U.S. patent application number 12/172082 was filed with the patent office on 2009-07-09 for multilane vehicle information capture system.
This patent application is currently assigned to Jim Allen. Invention is credited to Jim ALLEN, Balaraju Banna, Brijesh Rai Chawla, Shyamnath Harinath, Sangmesh Reddy, Fajie Sun, Raghavan Venugopal, Tiegang Xie, Sheng Zhong.
Application Number | 20090174778 12/172082 |
Document ID | / |
Family ID | 40844149 |
Filed Date | 2009-07-09 |
United States Patent
Application |
20090174778 |
Kind Code |
A1 |
ALLEN; Jim ; et al. |
July 9, 2009 |
MULTILANE VEHICLE INFORMATION CAPTURE SYSTEM
Abstract
A system and method for accurate express tolling of highway
vehicles. A multilane tolling system comprises a tolling (MVIC)
unit that collects information from tolling subsystems arranged to
take various vehicle measurements. Preferably, an intelligent
vehicle identification subsystem sends vehicle information to the
MVIC unit many times per second. Preferably, a vision tracking
system (VTS) communicates with the MVIC unit and sends the latter
information about the vehicle position using vision tracking
sensors. Preferably, an RF subsystem conducts multiple reads of a
transponder on a passing vehicle and forwards the read information
to the MVIC unit. Preferably, a vehicle image capture unit (VICU)
captures images of the passing vehicle when a camera in the VICU
receives a trigger from the MVIC unit. Preferably, a driver alert
module is used alert a driver passing through a tolling point as to
account balance associated with a silent toll tag or pay by plate
system.
Inventors: |
ALLEN; Jim; (Wetumpka,
AL) ; Zhong; Sheng; (Montgomery, AL) ;
Venugopal; Raghavan; (Montgomery, AL) ; Xie;
Tiegang; (Montgomery, AL) ; Sun; Fajie;
(Montgomery, AL) ; Reddy; Sangmesh; (Montgomery,
AL) ; Chawla; Brijesh Rai; (Montgomery, AL) ;
Banna; Balaraju; (Montgomery, AL) ; Harinath;
Shyamnath; (Montgomery, AL) |
Correspondence
Address: |
PILLSBURY WINTHROP SHAW PITTMAN, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Assignee: |
Allen; Jim
Wetumpka
AL
|
Family ID: |
40844149 |
Appl. No.: |
12/172082 |
Filed: |
July 11, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11138271 |
May 27, 2005 |
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12172082 |
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10953858 |
Sep 30, 2004 |
7071840 |
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11138271 |
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10206972 |
Jul 30, 2002 |
6864804 |
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10953858 |
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10098131 |
Mar 15, 2002 |
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10206972 |
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09977937 |
Oct 17, 2001 |
7136828 |
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10098131 |
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60574998 |
May 28, 2004 |
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60574997 |
May 28, 2004 |
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60574999 |
May 28, 2004 |
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60574996 |
May 28, 2004 |
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Current U.S.
Class: |
348/149 ;
348/E7.085 |
Current CPC
Class: |
G07B 15/063 20130101;
G08G 1/017 20130101; G08G 1/042 20130101; Y10S 707/92 20130101 |
Class at
Publication: |
348/149 ;
348/E07.085 |
International
Class: |
H04N 7/18 20060101
H04N007/18 |
Claims
1. A vehicle tracking system for tracking of a passing vehicle in a
highway environment, comprising: at least one capture unit for
continuously capturing vehicle images from the passing vehicle; a
set of lane straddling sensors arranged at a location on the
highway near the capture unit and providing vehicle position
information; an image capture program operable on the capture unit
to provide trajectory information using the captured vehicle
images; and a central process unit that compares the vehicle
position information and trajectory information associated with the
passing vehicle.
2. The system of claim 1, wherein the capture unit comprises a
videocamera and a video tracker light for illuminating the passing
vehicle.
3. The system of claim 1, wherein the capture unit is positioned on
a gantry located over at least one lane of the highway.
4. The system of claim 2, wherein the video camera is positioned in
line with a lane straddling sensor.
5. The system of claim 2, wherein the video camera is positioned
between borders of a lane containing a pair of adjacent lane
straddling sensors.
6. The system of claim 1, wherein the image capture program
comprises: a stabilization process to stabilize pixels to account
for camera movement; an identification process to locate moving
objects within the continuously captured vehicle images; a
segmentation process to group together pixels associated with a
moving object; and a trajectory calculating process to plot a
trajectory of a moving object.
Description
RELATED APPLICATIONS
[0001] This application is a Divisional application under 35 U.S.C.
.sctn.121 of co-pending U.S. application Ser. No. 11/138,271, filed
May 27, 2005, which is a continuation-in-part ("CIP") application
of U.S. patent application Ser. No. 10/953,858, filed Sep. 30,
2004, which is a continuation of U.S. patent application Ser. No.
10/206,972, now U.S. Pat. No. 6,864,804,which is a CIP application
of U.S. patent application Ser. No. 10/098,131, filed Mar. 15,
2002, which is a CIP application of U.S. patent application Ser.
No. 09/977,937, filed Oct. 17, 2001, all of which are incorporated
by reference herein in their entirety. This application further
claims the benefit of priority of the filing dates of U.S.
provisional Application Nos. 60/574,996, 60/574,997, 60/574,998,
and 60/574,999, all filed May 28, 2004, the contents of which are
also incorporated herein by reference.
[0002] This The above patent and all the above applications are
incorporated herein by reference in their entirety.
BACKGROUND
[0003] 1. Field of the Invention
[0004] The present invention relates generally to detection,
identification, and classification of metallic objects, and more
particularly, to a system and method for using ferromagnetic loops
to identify and classify vehicles.
[0005] 2. Background of the Invention
[0006] A typical automatic toll collection system for a highway
involves the use of a toll collection station or toll booth
positioned between each lane of traffic. Vehicles driving on the
highway must pass through a toll lane alongside the toll collection
station.
[0007] The passage of vehicles by the toll collection stations is
monitored with a combination of loop detectors, treadles, or other
such devices capable of detecting passing vehicles. These devices
provide vehicle classification information after the vehicle has
passed a payment point. Although these devices can be used for
audit purposes, they do not address the potential for error when an
attendant makes a mistake, nor do they address the ability to
properly classify all transactions.
[0008] In early toll collection systems, attendants were employed
to manually collect fares from the operators of vehicles and to
regulate the amount of tolls. Utilizing attendants to collect fares
involves numerous problems including, but not limited to, the
elements of human error, inefficiencies, traffic delays resulting
from manually collected tolls, employment costs of toll attendants,
and embezzlement or theft of collected toll revenues. As a result,
devices have been developed to automatically operate toll
collection systems without the need for toll attendants. In these
systems, the toll fees paid can be based on a combination of the
number of axles on a vehicle as well as a set price per
vehicle.
[0009] However, known tolling systems designed to operate without a
toll booth attendant intervention are typically based on several
heterogeneous components that are not optimized to work
together.
[0010] One example of a toll system that can collect tolls of
different toll rates from different classes or categories of
vehicles without user intervention is described in the '937
application. The '937 application discloses an intelligent vehicle
identification system (IVIS) that includes one or more inductive
loops. The inductive loops disclosed in the '937 application
includes signature loops, wheel assembly loops, intelligent queue
loops, wheel axle loops, gate loops, vehicle separation loops, and
enforcement loops.
[0011] The '972 application discloses additional designs,
configurations, installation, and other characteristics associated
with the loops previously disclosed in the '937 application. In
other words, a ferromagnetic loop in accordance with the teaching
of the '972 application can be adapted to be utilized as one or
more of the loops disclosed in the '937 application. Of course, the
ferromagnetic loops of the '972 application have applications
beyond those in the toll road context and those disclosed in the
'937 application. For example, the ferromagnetic loops of the '937
application can be adapted to serve various purposes including
traffic law enforcement, traffic surveys, traffic management,
detection of concealed metallic objects, treasure hunting, and the
like.
[0012] The present CIP application provides additional description
to the '972 application, and claims additional aspects of the
invention disclosed in the '972 application.
SUMMARY OF THE INVENTION
[0013] A ferromagnetic loop of the present invention has many
applications. For example, it can be used to detect metallic
objects, sensing moving vehicles, and classifying vehicles for toll
road applications. A preferred embodiment of the ferromagnetic loop
is characterized by a continuous wire. Preferably, the continuous
wire is shaped in a serpentine manner. Preferably, the continuous
wire is shaped in the serpentine manner on a plane having a
footprint. The footprint has an axis. A frequency associated with
the ferromagnetic loop is affected when there is a relative motion
between the ferromagnetic loop and a metallic object along the axis
of the footprint. For example, the frequency fluctuates when the
object moves along the axis above the ferromagnetic loop.
Similarly, the frequency can fluctuate if the ferromagnetic loop
moves in a direction along the axis above the object.
[0014] The footprint can take one of several shapes. For example,
the footprint can be one of a triangle, a rectangle, a square, a
circle, an ellipse, a rhombus, a parallelogram, and the like.
Preferably, the continuous wire forms multiple contiguous polygons
within the footprint. Preferably, each of the multiple contiguous
polygons can assume one of several shapes. For example, each of the
contiguous polygons can be one of a rectangle, a square, a rhombus,
a parallelogram, and the like. Preferably, there are at least three
contiguous polygons within the footprint. The contiguous polygons
may be parallel, perpendicular, or at an angle with respect to the
axis of footprint.
[0015] Each of the multiple contiguous polygons is associated with
a spacing dimension. The spacing dimension may be constant for all
the contiguous polygons. Alternatively, there may be different
spacing dimensions among the polygons. For example, the spacing
dimensions of the contiguous polygons may demonstrate a gradient
characteristic as shown in loop 4900 in FIG. 49.
[0016] In a specific implementation for vehicle detection
applications, the present invention provides a ferromagnetic loop
that is installed on a travel path for detection of vehicles moving
in a direction along the travel path. In the specific
implementation as shown in FIG. 27, ferromagnetic loop 2700 is
characterized by continuous wire 2702, which is shaped in a
serpentine manner within footprint 2704. Footprint 2704 has
footprint length dimension 2706, which is parallel to direction
2710 and footprint width dimension 2708, which is perpendicular to
direction 2710. Continuous wire 2702 forms multiple contiguous
polygons 2712 within footprint 2704. Each of multiple contiguous
polygons 2712 is characterized by polygon length dimension 2716
that is parallel to direction 2710 and polygon width dimension 2718
that is perpendicular to direction 2710. Polygon length dimension
2716 is also known as the spacing dimension. A frequency associated
with ferromagnetic loop 2700 is affected when a vehicle (not shown)
moves across footprint 2704 in direction 2710. The detection of the
vehicle can be done using loop detector 2720, which is connected to
continuous wire 2702 via lead-in 2714.
[0017] In one embodiment, each of polygon width dimensions 2718 is
substantially equal to footprint width dimension 2708 and a sum of
all the polygon length dimensions 2716 is substantially equal to
footprint length dimension 2706. In a different embodiment, any of
polygon length dimensions 2716 is as long as any other polygon
length dimensions 2716. In still a different embodiment, one or
more of polygon length dimensions 2716 is longer than at least one
other polygon length dimension 2716. In other words, the spacing
dimension 2716 between any two contiguous polygons may be the same
or vary.
[0018] In a different preferred embodiment of the ferromagnetic
loop shown in FIG. 49A, ferromagnetic loop 4910 includes left loop
4912 and right loop 4914. Left loop 4912 is characterized by a left
footprint with a left length dimension parallel to the direction
and a left width dimension perpendicular to the direction.
Similarly, the right loop is characterized by a right footprint
with a right length dimension parallel to the direction and a right
width dimension perpendicular to the direction. Left loop 4912 and
the right loop 4914 are part of a continuous wire that is
characterized by overall footprint 4920 having overall length
dimension 4922 parallel to the direction and overall width
dimension 4924 perpendicular to the direction. Left loop 4912 and
right loop 4912 are located offset relative to each other such that
a sum of the left length dimension and the right length dimension
equals overall length dimension 4922, and a sum of the left width
dimension and the right width dimension equals overall width
dimension 4924. When a vehicle moves in the direction over the
ferromagnetic loop, a left portion of the vehicle's wheel assembly
affects a first frequency associated with left loop 4912 and a
right portion of the vehicle's wheel assembly affects a second
frequency associated with right loop 4914. Each of left loop 4912
and right loop 4914 can assume one of several shapes. For example,
the shape for each of the left loop and the right loop can be one
of a rectangle, a square, a rhombus, a parallelogram, and the
like.
[0019] In another embodiment shown in FIG. 49B, the present
invention provides a different loop array 4950 for detection of
vehicles moving in a direction. Loop array 4950 includes front loop
4952 and rear loop 4954. Each of front loop 4952 and rear loop 4954
is associated with a frequency that is quantifiable by loop
detector 4902 in communication with loop array 4950. The frequency
associated with each of front loop 4952 and rear loop 4954 is
affected when a vehicle moves across each of front loop 4952 and
rear loop 4954 in direction 4906. Preferably, at least one of front
loop 4952 and rear loop 4954 is characterized by multiple
contiguous polygons. Preferably, at least one of front loop 4952
and rear loop 4954 is characterized by a continuous wire shaped in
a serpentine manner to form the multiple contiguous polygons.
Preferably, at least one of front loop 4952 and rear loop 4954 is
characterized by a footprint having a loop length dimension and a
loop width dimension, and each of the multiple polygons associated
with the loop is characterized by a polygon length dimension and a
polygon width dimension. Preferably, the sum of all polygon length
dimensions is substantially equal to the loop length dimension, and
each of the polygon length dimensions is substantially equal to the
loop length dimension.
[0020] The present invention further provides methods for
installing a ferromagnetic loop for detection of vehicles. A
preferred method includes the step of providing a web of grooves on
a traveling lane. The web of grooves is characterized by multiple
contiguous polygons. The method further includes the step of laying
a continuous wire in a serpentine manner within the web of grooves.
The method also includes the step of securing the continuous wire
within the web of grooves using a bonding agent. Preferably, the
method can further include the step of laying the continuous wire
at least two turns in at least one groove of the web of grooves.
Preferably, the at least two turns are laid side-by-side within the
at least one groove. Preferably, the web of grooves has a spacing
between any two parallel grooves. The spacing may be from about
three inches to about eight inches. Furthermore, the web of grooves
may have a gradient spacing between the parallel grooves. The
gradient spacing can range from between about three inches and
about eight inches.
[0021] The present invention further includes a method for
preparing a ferromagnetic loop. The method includes the step of
pre-forming a continuous wire shaped in a serpentine manner to form
multiple contiguous polygons. The method also includes the step of
attaching one or more fasteners along the continuous wire to
maintain the multiple contiguous polygons. The fasteners are
adapted to maintain the multiple contiguous polygons. The method
can further include the step of providing at least two turns of the
continuous wire to form at least one of the multiple contiguous
polygons. The at least two turns of the continuous wire are
preferably arranged side-by-side.
SUMMARY OF THE INVENTION
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a schematic diagram illustrating a vehicle
traveling through a path on which a classification loop array of
the present invention is located.
[0023] FIG. 1A is a schematic diagram illustrating preferred
locations of a classification loop array and an intelligent queue
loop.
[0024] FIG. 2 is a schematic diagram illustrating one embodiment of
the present invention as implemented in a toll road
application.
[0025] FIG. 3 is a schematic diagram illustrating another
embodiment of the present invention as implemented in a toll road
application.
[0026] FIG. 4 is a schematic diagram illustrating another
embodiment of the present invention as implemented in a toll road
application.
[0027] FIG. 5 is a schematic diagram illustrating another
embodiment of the present invention as implemented in a toll road
application.
[0028] FIG. 6 depicts exemplary signature information of a vehicle
traveling at a speed of ten miles per hour over a six feet by six
feet signature loop.
[0029] FIG. 7 depicts other exemplary signature information of the
same vehicle that comes to a complete stop at one time over the six
feet by six feet signature loop.
[0030] FIG. 8 depicts exemplary wheel assembly information of a
two-axle vehicle traveling over a wheel assembly loop at ten miles
per hour.
[0031] FIG. 9 depicts exemplary signature information of a vehicle
traveling at a speed of five miles per hour over a six feet by six
feet signature loop.
[0032] FIG. 10 depicts other exemplary signature information of a
vehicle traveling at a speed of 10 miles per hour over a signature
loop.
[0033] FIG. 11 depicts exemplary signature information of a vehicle
traveling at a speed of 30 miles per hour over a six feet by six
feet signature loop.
[0034] FIG. 12 depicts exemplary wheel assembly information of a
two-axle vehicle traveling over a wheel assembly loop.
[0035] FIG. 13 depicts exemplary signature information of a vehicle
traveling over an enforcement loop.
[0036] FIG. 14 depicts other exemplary wheel assembly information
of a two-axle vehicle traveling over a wheel assembly loop.
[0037] FIG. 15 is a diagram showing a view from a toll collection
station indicating that as a vehicle approaches the toll collection
station, the vehicle is classified and a fare is determined without
input from a toll attendant.
[0038] FIG. 16 is a screenshot indicating the classification for
the vehicle shown in FIG. 15 and a fare associated with the
classification.
[0039] FIG. 17 is a screenshot showing an image of a vehicle
category retrievable from a vehicle library that is accessible to
an intelligent vehicle identification unit.
[0040] FIG. 18 is a screenshot showing an image of another vehicle
category retrievable from a vehicle library that is accessible to
an intelligent vehicle identification unit.
[0041] FIG. 19 is a screenshot of the intelligent vehicle
identification unit of the present invention, indicating that the
vehicle library can be reviewed, updated, or otherwise modified
through a graphical user interface.
[0042] FIG. 20 is a screenshot of the intelligent vehicle
identification unit of the present invention, illustrating that
details of each transaction record can be stored in a database.
[0043] FIG. 21 depicts exemplary initial signature information
indicating a vehicle traveling at one speed over a signature loop
and an exemplary subsequent signature information indicating the
same vehicle traveling at another speed over an intelligent queue
loop.
[0044] FIG. 22 depicts exemplary signature information of a
four-axle vehicle.
[0045] FIG. 23 depicts exemplary signature information of a vehicle
towing a two-axle trailer.
[0046] FIG. 24 depicts exemplary signature information of a
five-axle truck.
[0047] FIG. 25 depicts exemplary signature information of a
three-axle dump truck as detected by an intelligent queue loop.
[0048] FIG. 26 is a schematic diagram showing the flow of
information among various components of the present invention.
[0049] FIG. 27 is schematic diagram showing characteristics
associated with a ferromagnetic loop of the present invention.
[0050] FIG. 28 is schematic diagram showing different wheel sizes
of typical vehicles.
[0051] FIG. 29 is schematic diagram showing the layout of a known
inductive loop design.
[0052] FIGS. 29A, 29B, 29C, 29D, and 29E are frequency vs. time
plots obtained using known loops of an existing technology.
[0053] FIG. 30 is schematic diagram showing the layout of another
known inductive loop design.
[0054] FIGS. 30A, 30B, 30C, 30D, and 30E are frequency vs. time
plots obtained using known loops of an existing technology.
[0055] FIG. 30F is schematic diagram showing the layout of a known
"coil within a coil design" loop technology.
[0056] FIG. 31 is schematic diagram illustrating a layout of two
ferromagnetic loops of the present invention.
[0057] FIG. 31A is schematic diagram illustrating a gradient
diagonal loop of the present invention.
[0058] FIG. 31B is schematic diagram showing an installation of the
ferromagnetic loop of the present invention.
[0059] FIG. 32 is schematic diagram showing a different embodiment
of the present invention.
[0060] FIGS. 33, 33A, 34, 35, 36, 37, and 38, are frequency vs.
time plots produced using a ferromagnetic loop of the present
invention.
[0061] FIG. 39 is schematic diagram showing different embodiments
of the present invention.
[0062] FIG. 40 is a schematic diagram showing how a continuous wire
can be shaped in a serpentine manner to form a ferromagnetic loop
of the invention.
[0063] FIG. 41 is a cross-sectional view along line A-A of FIG.
40.
[0064] FIG. 42 is an alternative cross-sectional view along line
A-A of FIG. 40.
[0065] FIG. 43 is another alternative cross-sectional view along
line A-A of FIG. 40.
[0066] FIGS. 43A, 43B, 43C, and 43D are frequency vs. time plots
produced using a ferromagnetic loop of the present invention.
[0067] FIG. 44 is a cross-sectional view of a ferromagnetic loop of
the present invention.
[0068] FIGS. 44A, 44B, 44C, 44D, and 44E are frequency vs. time
plots produced using a ferromagnetic loop of the present
invention.
[0069] FIG. 45 is schematic diagram showing different embodiments
of the present invention.
[0070] FIGS. 45A, 45B, 45C, 45D, 45E, 45F, 45G, 45H, and 45I are
frequency vs. time plots produced using a ferromagnetic loop of the
present invention.
[0071] FIGS. 46 and 46A are schematic diagrams showing
ferromagnetic loops of the present invention with offset left and
right segments.
[0072] FIGS. 46B, 46C, 46D, 46E, 46F, and 46G are schematic
diagrams showing how a ferromagnetic loop of the present invention
can be shaped using a continuous wire.
[0073] FIG. 47 is schematic diagram showing an offset loop of the
present invention having a left segment and a right segment offset
by a distance.
[0074] FIGS. 47A, 47B, 47C, 47D, 47E, 47F, 47G, 48A, 48B, 48C, 48D,
48E, and 48F are frequency vs. time plots produced using a
ferromagnetic loop of the present invention.
[0075] FIG. 49, 49A, 49B, and 49C are schematic diagrams showing
additional embodiments of the present invention.
[0076] FIGS. 50 and 51 are schematic diagrams showing additional
embodiments of the present invention involving loop arrays.
[0077] FIG. 52 is a schematic diagram showing a cross-sectional
view of an anchor or a locking mechanism of the present
invention.
[0078] FIG. 53 is a schematic diagram showing alternative anchors
of the present invention.
[0079] FIG. 54 is a schematic diagram showing a cross-sectional
view of a ferromagnetic loop of the present invention.
[0080] FIG. 55 is a schematic diagram showing a preferred
embodiment of the present invention.
[0081] FIGS. 55A, 55B, and 55C are frequency vs. time plots
produced using a ferromagnetic loop of the present invention.
[0082] FIG. 56 is a schematic diagram showing another preferred
embodiment of the present invention.
[0083] FIGS. 56A, 56B, and 56C are frequency vs. time plots
produced using a ferromagnetic loop of the present invention.
[0084] FIG. 57 is a schematic diagram of another preferred
embodiment of the present invention.
[0085] FIGS. 57A and 57B are frequency vs. time plots produced
using a ferromagnetic loop of the present invention.
[0086] FIG. 58 depicts a block diagram of a toll violation
enforcement system (VES), according to an exemplary embodiment of
the present invention.
[0087] FIG. 59 discloses details of an application program
according to one embodiment of the present invention.
[0088] FIG. 60 depicts details of operation of a plate location
module according to an exemplary embodiment of the present
invention.
[0089] FIG. 61 shows images captured using a capture unit according
to a preferred embodiment of the present invention.
[0090] FIG. 62 illustrates details of operation of a plate location
module according to an embodiment of the present invention.
[0091] FIG. 63 illustrates operation of an image enhancement module
according to another embodiment of the present invention.
[0092] FIG. 64 depicts interoperation of an image compression
module with other modules according to an embodiment of the present
invention.
[0093] FIG. 65 illustrates exemplary features of a violation
enforcement system according to an embodiment of the present
invention.
[0094] FIG. 66 illustrates exemplary steps for a method for toll
violation enforcement according to an exemplary embodiment of the
present invention.
[0095] FIG. 67 illustrates components of an MVIC system according
to an exemplary embodiment of the present invention.
[0096] FIG. 68 depicts a relative arrangement employed for an RF
read system and an IVIS system according to one embodiment of the
present invention.
[0097] FIG. 69 depicts additional sensors used in an IVIS system
according to an exemplary embodiment of the present invention.
[0098] FIG. 70 depicts a scenario in which an MVIC arrangement of
the present invention is used to detect a vehicle that straddles
two travel lanes.
[0099] FIG. 71 displays a typical frequency is time plot for a two
axle vehicle, taken by a gradient sensor arranged according to an
embodiment of the present invention.
[0100] FIG. 72 illustrates exemplary steps involved in a method for
determining a vehicle position using IVIS and RF data, according to
an exemplary embodiment of the present invention.
[0101] FIG. 73 depicts a scenario where a vehicle passes lane
straddling sensors arranged according to another embodiment of the
present invention.
[0102] FIG. 74 illustrates a scenario in which two vehicles in two
adjacent lanes pass through an MVIC arrangement of the present
invention at the same time.
[0103] FIG. 75 illustrates exemplary steps involved in a method for
determining the simultaneous presence of more than one vehicle in
an MVIC area using lane straddling sensors, according to an
exemplary embodiment of the present invention.
[0104] FIG. 76 illustrates a scenario in which two lane straddling
sensors of the present invention are activated when a vehicle
travels entirely within a single travel lane.
[0105] FIG. 77 illustrates a scenario in which two lane straddling
sensors of the present invention are activated when two vehicles
each travel directly over one sensor.
[0106] FIG. 78 illustrates a scenario in which two cars traveling
through adjacent lanes that only trigger two lane straddling
sensors to activate.
[0107] FIG. 79 illustrates exemplary steps for implementing a "read
zone prediction" process to accurately identify a vehicle,
according to an exemplary embodiment of the present invention.
[0108] FIG. 80 depicts a side view of a portion of an MVIC
arrangement, according to an exemplary embodiment of the present
invention.
[0109] FIGS. 81a-81d show a series of images of vehicle images
recorded using a vision tracking system according to one embodiment
of the present invention.
[0110] FIGS. 82a-82d display the results of motion analysis
collected for moving vehicle 8102 of FIG. 81.
[0111] FIG. 83 displays images from FIGS. 82a to 82d superimposed
on the same frame.
[0112] FIG. 84 illustrates a tandem RF read zone geometry employed
in conjunction with an IVIS sensor array according to another
exemplary embodiment of the present invention.
[0113] FIG. 85 depicts exemplary steps involved in a method for
conducting multiple RF transactions with vehicle passing through a
tandem RF read zone, according to a preferred embodiment of the
present invention.
[0114] FIG. 86 illustrates a sensor arrangement in a multiple
sensor array according to an embodiment of the present
invention.
[0115] FIG. 87 shows a control page of a master program for
controlling sampling periods in a multilane IVIS system, according
to a preferred embodiment of the present invention.
[0116] FIG. 88 illustrates a "four diamond one VTS" configuration,
according to an embodiment of the present invention.
[0117] FIG. 89 illustrates a "three diamond VTS" arrangement
according to another embodiment of the present invention.
[0118] FIG. 90 illustrates exemplary steps involved in a method for
vehicle tracking, according to an embodiment of the present
invention.
[0119] FIG. 91 illustrates another MVIC system, arranged according
to a further embodiment of the present invention.
[0120] FIG. 92 illustrates an embodiment of the present invention
in which a visible light signal is arranged within or above the
roadway.
[0121] FIG. 93 illustrates another embodiment of the invention, in
which multiple lighting sources are employed in travel lanes to
alert a passing vehicle as to toll account status.
DETAILED DESCRIPTION OF THE INVENTION
[0122] Overview of the '937 Application
[0123] It is noted the present invention can be adapted for a large
number of different applications. For example, the profile
information generated by a classification loop array using the
present invention can be used in traffic management and analysis,
traffic law enforcement, and toll collection.
[0124] FIG. 1 is a schematic diagram illustrating a preferred
location of classification loop array 110 of the present invention
on the surface of path 100. Path 100 can be, for example, a toll
lane, a roadway, an entrance to a parking lot, or any stretch of
surface on which vehicle 120 travels in direction 130.
Classification loop array 110 is located at a distance D upstream
from device 150 along path 100.
[0125] Classification loop array 110 comprises at least one
signature loop and at least one wheel assembly loop. Briefly, the
signature loop is adapted to indicate changes in electromagnetic
field which can be processed to produce initial signature
information as it detects the presence of vehicle 120 over it. The
initial signature information represents changes of inductance
which can be interpreted to identify, among other characteristics
of vehicle 120, a speed of the vehicle, an axle separation of the
vehicle, and a chassis height of the vehicle. The wheel assembly
loop is adapted to indicate changes in electromagnetic field which
can be processed to produce wheel assembly information as it
detects the presence of vehicle 120 over it. The wheel assembly
information represents changes of inductance which can be
interpreted to identify, among other attributes of vehicle 120, the
axle count and the axle separation with increased accuracy and
details. Specifically, the wheel assembly loop can detect, among
other things, the separation between two successive wheels of
vehicle 120 that is traveling in direction 130. The initial
signature information and the wheel assembly information,
collectively, are also known as profile information of the
vehicle.
[0126] Device 150 is in communication with classification loop
array 110. As discussed below, device 150 can be one of many
different devices that can be used in conjunction with
classification loop array 110. Although device 150 is shown in FIG.
1 to be located downstream of classification loop array 110 in
direction 130, device 150 can be located elsewhere, for example, at
a position upstream of classification loop array 110. In another
example, device 150 can located next to classification loop array
110. In still another example, device 150 can be at a remote
location. Distance D can be any distance depending on specific
applications. In a toll collection application in which path 100 is
a toll lane, distance D can be between zero and 110 feet.
Preferably, distance D is about 65 feet. It is noted that a length
of 65 feet is slightly longer than then the length of a typical
tractor trailer. The distance D should be increased to about 85
feet to 110 feet for toll lanes that are adapted to accommodate
tractor-trailers towing double trailers. Similarly, the distance D
can be shorter than 65 feet if tractor trailers are not expected to
use path 100.
[0127] In a traffic management and analysis application,
classification loop array 110 can be arranged such that it can be
used to sense movement of vehicle 120 along path 100 in direction
130. For example, path 100 can be a specific stretch of a highway.
In this application, device 150 can be, for example, a computer
adapted to perform statistical analysis based on data collected by
classification loop array 110. Device 150 can, for example, use the
data collected by classification loop array 110 to determine the
types of vehicles that use the highway, the number of vehicles
passing that point each day, the speed of the vehicles, and so
on.
[0128] In a traffic law enforcement application, classification
loop array 110 can be used in conjunction with other devices. For
example, device 150 can be a camera that is positioned to take a
photograph of the license plate of vehicle 120 if classification
loop array 110 detects a speed of vehicle 120 exceeding a speed
limit. In still another example, path 100 is a restricted lane that
prohibits large vehicles such as tractor trailers and device 150 is
a camera used to capture an image of the license plate of vehicle
120 if classification loop array 110 detects the presence of a
tractor trailer in path 100.
[0129] In a toll collection application in which device 150 is a
payment point (e.g., an automated toll collection mechanism),
profile information associated with vehicle 120 that is collected
by classification loop array 110 can be used to classify vehicle
120 before it arrives at the payment point. The classification can
then be used to notify an operator of vehicle 120 about an
appropriate fare associated with the classification. In this toll
collection application, vehicle 120 is classified and the
appropriate fare is determined before it arrives at device 150.
More importantly, the classification is made without input from a
toll attendant, thereby eliminating human errors associated with
classification of vehicles. When vehicle 120 arrives at device 150,
the appropriate fare can be collected from the operator. It is
noted that device 150 can be replaced by a toll attendant even
though in this application the toll attendant does not classify
vehicle 120 to determine the fare. In the toll collection
application of the present invention, it is preferable that vehicle
120 clears classification loop array 110 (i.e., the entire vehicle
120 must clear classification loop array 110 before vehicle 120
reaches device 150.
PREFERRED EMBODIMENTS FOR IMPLEMENTATION IN A TOLL LANE
[0130] FIG. 1A is a schematic diagram illustrating the layout of
components of another preferred embodiment of the present
invention. In this preferred embodiment, path 100 is a toll lane on
which vehicle 120 travels in direction 130. Device 150 is a payment
point. Classification loop array 110 is located at a distance D
upstream of device 150. At or near device 150, intelligent queue
loop 140 is located on toll lane 100 downstream of classification
loop array 110. Intelligent vehicle identification unit 170 is in
communication with classification loop array 110, intelligent queue
loop 140, and device 150.
[0131] Preferably, classification loop array 110 has a length and a
width. The width is preferably wide enough so that no vehicle can
travel on toll lane 100 without being detected by classification
loop array 110. The length, indicated in FIG. 1A as length L, is
preferably between about three and thirty feet. Preferably,
classification loop array 110 comprises at least one signature loop
that measures six feet by six feet. Intelligent queue loop 140
preferably has a length and width that is similar to the signature
loop. In other words, intelligent queue loop 140 is also preferably
six feet by six feet.
[0132] In this embodiment, the signature loop (not shown in FIG.
1A) of classification loop array 110 is adapted to indicate changes
in electromagnetic field which can be processed to produce initial
signature information of vehicle 120. Intelligent queue loop 140 is
adapted to indicate changes in electromagnetic field which can be
processed to produce subsequent signature information of vehicle
120. The initial and subsequent signature information of a common
vehicle exhibit similar characteristics on a inductance vs. time
plot. Exemplary inductance vs. time plots are shown in FIGS. 6-7,
9-11, 13, and 21-25. The Y-axis represents a unit of inductance and
the X-axis represents a unit of time. Preferably, the unit of
inductance is in kilo-henrys and the unit of time is in
milli-seconds.
[0133] Preferably, classification loop array 110 further comprises
at least one wheel axle loop (not shown in FIG. 1A). The wheel axle
loop is adapted to indicate changes in electromagnetic field which
can be processed to produce wheel assembly information. The wheel
assembly information can be represented in an inductance vs. time
plot. Exemplary inductance vs. time plots of wheel assembly
information is shown in FIGS. 8, 12, and 14.
[0134] Intelligent vehicle identification unit 170 is in
communication with classification loop array 110, intelligent queue
loop 140, and device 150. In the preferred embodiment, when vehicle
120 is traveling over classification loop array 110, profile
information of vehicle 120 is generated and provided to intelligent
vehicle identification unit 170. As noted above, the profile
information represents changes of inductance which can be
interpreted to identify, among other characteristics of vehicle
120, an axle count of the vehicle, an axle spacing of the vehicle,
a speed of the vehicle, and a chassis height of the vehicle.
[0135] As suggested above, the profile information includes initial
signature information that is produced based at least in part on
data collected by the signature loop of classification loop array
110. Preferably, the profile information also includes wheel
assembly information that is produced based at least in part on
data collected by the wheel assembly loop. When vehicle 120 travels
over intelligent queue loop 140, subsequent signature information
is produced based at least in part on data collected by intelligent
queue loop 140. The profile information and the subsequent
signature information are provided to intelligent vehicle
identification unit 170.
[0136] If the initial signature information and the subsequent
signature information indicate that the vehicle previously detected
by classification loop array 110 is now at device 150, intelligent
vehicle identification unit 170 notifies the operator of vehicle
120 of the appropriate fare associated with the profile
information. In other words, intelligent queue loop 140 verifies
that that the vehicle at device 150 is the same vehicle for which
the fare was determined from classification loop array 110. This
serves to detect if one or more vehicles have disturbed the queue
order.
[0137] FIG. 2 is a schematic diagram illustrating one embodiment of
the present invention as implemented in a toll road application.
Classification loop array 200 comprises a number of loops,
including, for example, one or more signature loops 210 and 230,
and at least one wheel assembly loop 220. Signature loops 210 and
230, and wheel assembly loop 220, are arranged such that a vehicle
traveling in direction 130 would initially encounter front
signature loop 210, and then wheel assembly loop 220, and finally
rear signature loop 230.
[0138] In addition to classification loop array 200, the preferred
embodiment shown in FIG. 2 further comprises intelligent queue loop
240 and gate loop 250. Intelligent queue loop 240 is preferably
similar to signature loops 210 and 230 in shape and dimensions.
Gate loop 250 is adapted to detect the presence of the vehicle
beyond or downstream of toll gate 252. Preferably, toll gate 252 is
kept open until the vehicle clears gate loop 250.
[0139] Each of front signature loop 210, rear signature loop 230,
and intelligent queue loop 240 is preferably generally rectilinear
or rectangular in shape. Preferably, each of these loops has two or
more turns of wire. The width of each of these loops is preferably
six feet. However, the width can be almost as wide as toll lane
100. In an example in which toll lane 100 is 12 feet wide, the
width of each of these loops can be between about three feet and
about eleven feet. Preferably, each of these loops is a square, in
other words, the length of each of these loops is the same as the
width. Preferably, each of these loops measures six feet by six
feet.
[0140] Each of front signature loop 210, rear signature loop 230,
intelligent queue loop 240, and gate loop 250 is basically an
inductive loop. Each of these loops is used to detect, among other
things, a presence of a vehicle over it, the vehicle's chassis
height, an axle count of the vehicle, and the movement of the
vehicle. Each of these loops preferably produces a flux field or an
electromagnetic field that is high enough to be affected by the
chassis of each vehicle that uses toll lane 100. The chassis of the
vehicle creates eddy currents and disperses the flux field of the
loop. This results in lowering the inductance of the loop circuit.
One of skill in the art could consult Traffic Detector Handbook,
Publication No. FHWA-IP-90-002, which is incorporated herein by
reference in its entirety, for further information regarding
inductive loops. The loop's detector (e.g., loop detector 260)
processes these inductive changes in the loop circuit.
[0141] Wheel assembly loop 220 is also an inductive loop.
Preferably, wheel assembly loop 220 is adapted to detect the wheel
assemblies of the vehicle and to minimize the detection of the
chassis of the vehicle and maximize the detection of the axles of
the vehicle. Wheel assembly loop 220 is adapted to indicate changes
in electromagnetic field which can be processed to produce wheel
assembly information.
[0142] Intelligent queue loop 240 preferably senses the beginning
of the vehicle, the end of the vehicle, the chassis height of the
vehicle, and the vehicle's presence over it. Gate loop 250 is
preferably adapted to detect the presence of the vehicle. The
detection of the vehicle by gate loop 250 controls toll gate
252.
[0143] Each of front signature loop 210, wheel assembly loop 220,
rear signature loop 230, intelligent queue loop 240, and gate loop
250 is in communication with one or more loop detector 260. Loop
detector 260 preferably has a loop signal processor and
discriminator unit (LSP&D) (not shown). Preferably, each of
front signature loop 210, rear signature loop 230, intelligent
queue loop 240, and gate loop 250 can be used to determined
signature information including one or more of vehicle presence,
vehicle speed, vehicle length, chassis height, and vehicle
movement. The signature information, as discussed above, can be
represented in an inductance vs. time plot.
[0144] FIG. 6 depicts an exemplary signature information of a
vehicle traveling at a speed of ten miles per hour over a six feet
by six feet signature loop. The speed can be calculated based on
the slope of curve 610. Point 612 indicates a moment in time when
the vehicle is first detected by the signature loop. Point 614
indicates a moment in time when the vehicle is at the center of the
signature loop. Point 616 indicates a moment in time when the
vehicle has gone beyond the detection zone of the signature
loop.
[0145] FIG. 7 depicts other exemplary signature information of the
same vehicle that comes to a complete stop at one time over the six
feet by six feet signature loop. Curve 710 represents the movement
of the vehicle over the signature loop. The flat portion of curve
710 between point 712 (at time=1027) and 714 (at time=1606)
indicates that the vehicle is stationary.
[0146] FIG. 9 depicts an exemplary signature information of a
vehicle traveling at a speed of five miles per hour over a six feet
by six feet signature loop. Curve 910 shows changes in inductance
detected by the signature loop as the vehicle moves over the
signature loop.
[0147] FIG. 10 depicts other exemplary signature information of a
vehicle traveling at a speed of 10 miles per hour over a signature
loop. Curve 1010 shows changes in inductance detected by the
signature loop as the vehicle moves over the signature loop.
[0148] FIG. 11 depicts an exemplary signature information of a
vehicle traveling at a speed of 30 miles per hour over a six feet
by six feet signature loop. Curve 1110 shows changes in inductance
detected by the signature loop as the vehicle moves over the
signature loop.
[0149] Note that each of curves 910, 1010, and 1110 exhibits a
similar pattern. Each of these curves shows that when the vehicle
is not detected, the inductance value is in between 121000 units
and 121200 units. Each of these curves also shows that when the
vehicle is in the center of the signature loop, the inductance
value is in between 120000 units and 120200 units. The noticeable
difference between these three curves is the width of the gap
between two points on the curve when the presence of the vehicle is
detected. Indeed, each of these curves characterizes the same
vehicle (incidentally, the vehicle is a pickup truck) moving at
speeds of five miles per hour, 10 miles per hour, and 30 miles per
hour, as represented by curves 910, 1010, and 1110, respectively,
over the same signature loop.
[0150] FIG. 13 depicts an exemplary signature information of the
same vehicle traveling over an enforcement loop or an intelligent
queue loop. Note that curve 1310 exhibits similar pattern of
inductance change over time as those characterized by curves 910,
1010, 1110.
[0151] FIG. 8 depicts an exemplary wheel assembly information of a
two-axle vehicle traveling over a wheel assembly loop at ten miles
per hour. Curve 810 indicates changes in inductance as the vehicle
travels over the wheel assembly loop. First peak 812 indicates the
detection of a front wheel of the vehicle. Second peak 814
indicates the detection of a rear wheel of the vehicle.
[0152] FIG. 12 depicts an exemplary wheel assembly information of a
two-axle vehicle traveling over a wheel assembly loop. Curve 1210
indicates changes in inductance as the vehicle travels over the
wheel assembly loop. First peak 1212 indicates the detection of a
front wheel of the vehicle. Second peak 1214 indicates the
detection of a rear wheel of the vehicle.
[0153] FIG. 14 depicts other exemplary wheel assembly information
of a two-axle vehicle traveling over a wheel assembly loop. Curve
1410 indicates changes in inductance as the vehicle travels over
the wheel assembly loop. First peak 1412 indicates the detection of
a front wheel of the vehicle. Second peak 1414 indicates the
detection of a rear wheel of the vehicle.
[0154] Referring now to FIG. 21, initial curve 2110 characterizes a
vehicle traveling at a first speed over a signature loop.
Subsequent curve 2120 characterizes the vehicle slowing down
significantly when it was detected by an intelligent queue loop
240. Both curve 2110 and curve 2120 have identical lowest
inductance between 119600 units and 119800 units, indicating that
each of curve 2110 and curve 2120 characterizes the same
vehicle.
[0155] FIGS. 22-25 are additional exemplary inductance vs. time
plots representing signature information of different categories of
vehicles. FIG. 22 depicts an exemplary signature information of a
four-axle vehicle. FIG. 23 depicts an exemplary signature
information of a vehicle towing a two-axle trailer. FIG. 24 depicts
an exemplary signature information of a five-axle truck. FIG. 25
depicts an exemplary signature information of a three-axle dump
truck.
[0156] Referring back to FIG. 2, intelligent vehicle identification
unit 270 comprises a microprocessor. The microprocessor is
preferably capable of gathering data from one or more distinct
inductive loop measurement and processing units such as loop
detector 260. One example of loop detector 260 is a microprocessor
that provides an oscillating circuit. Loop detector 260 can be
incorporated into intelligent vehicle identification unit 270. Loop
detector 260 receive the profile information from classification
loop array 200 and the subsequent signature information from
intelligent queue loop 240. Furthermore, intelligent vehicle
identification unit 270, given the signals received (which
comprises the profile information and the subsequent signature
information), can perform various calculations on the signals to
determine core information about a vehicle passing over the
inductive loops such as relative vehicle mass, vehicle length,
average passing speed of the vehicle, direction of movement of the
vehicle, number of axles present on the vehicle, and the spacing
between subsequent axles on the vehicle.
[0157] Intelligent identification unit 270 is in communication with
display and local interface 272 and remote access and interface
274. Intelligent identification unit 270 has access to a vehicle
library comprising predefined vehicle classifications or
categories, and their associated fares. The vehicle library can be
modified through a graphical user interface associated with
intelligent identification unit 270. Modification of the vehicle
library can involve, for example, adding, deleting, and editing of
vehicle categories. The modification can be performed through a
computer associated with a local area network with which
intelligent vehicle identification unit 270 is associated.
Preferably, the modification can also be performed through a
computer associated with a wide area network with which intelligent
vehicle identification unit 270 is associated.
[0158] Once the information received from loop detector 260 is
processed by intelligent vehicle identification unit 270, the
resultant signature data of the vehicle is utilized in a comparison
engine. The comparison engine employs both stored typical vehicle
signatures for various distinct categories of vehicles and neural
network processing to intelligently associate the exact data
received with a representative vehicle signature previously
defined. Also, the initial signature information is stored for
later comparison with the subsequent signature information received
from intelligent queue loop 240.
[0159] After processing this data against the vehicle library and
through the neural network processing, the microprocessor assigns a
distinct classification identifier to the vehicle and internally
queues the data thus received and awaits a detection signal from
intelligent queue loop 240. The vehicle library is preferably
stored in a database accessible by intelligent vehicle
identification unit 270.
[0160] Once the subsequent signature information is received from
intelligent queue loop 240 by the microprocessor, the
microprocessor performs an analysis on this signature information
to see if it properly represents the next internally queued vehicle
for purposes of ascertaining that the vehicle arriving at payment
point 290 is the same vehicle that the system expects to be
arriving at payment point 290. Under one circumstance, a vehicle,
e.g., a motorcycle, could potentially pass over classification loop
array 200 and then exit toll lane 100 early. In another instance,
the vehicle could potentially miss passing over classification loop
array 200 and move into toll lane 100 at a later point, thus
missing being correctly classified by the system beforehand.
Intelligent queue loop 240 is utilized in both circumstances to
detect such queuing anomalies.
[0161] The microprocessor that is utilized to analyze the various
loop signatures can preferably send data to another main processing
device to gather data, control traffic flow, or otherwise process
the data in a meaningful manner. In a toll collection embodiment of
the invention, this collection processing device would be another
microprocessor unit designed to assimilate various input data and
toll collection device control to assist in collecting proper fare
amounts for vehicles passing through the toll lane.
[0162] If a vehicle crosses intelligent queue loop 240 and is not
recognized as the next classified vehicle, the microprocessor will
check any other queued classified vehicles to see if the signature
matches any other vehicles thus queued. If the subsequent signature
information matches a later vehicle, then the microprocessor will
assume that any earlier queued vehicles have exited the lane after
crossing classification loop array 200 and will discard those
vehicles from the queue.
[0163] If a vehicle crosses intelligent queue loop 240 and is not
recognized as the next classified vehicle or as any of the vehicles
subsequent in the vehicle classification queue, the microprocessor
will then make the assumption that the vehicle entered toll lane
100 late and that it was not properly classified. A new vehicle
classification record will then be inserted into the queue at that
point and marked such that the system does not reliably know what
type of vehicle is currently at the head of the queue.
[0164] If a vehicle entered toll lane 100 late, thus causing an
anomaly in the proper queuing of vehicles, an appropriate message
will be sent from the microprocessor to the main processing device
so that the main processing device can make an appropriate decision
based on the type of anomaly that occurred in queuing and present
the toll attendant with the appropriate information for making an
informed decision on how to handle the errant vehicle, if the toll
lane is a manual collection lane. The collection-processing device
must make a decision on the expected toll based on rules
established by the authority (default fare) if the main processing
device is utilized to automatically operate a toll collection lane
without the use of a toll attendant.
[0165] Other than the previously specified anomaly situation in
queuing, the microprocessor will normally pass information
regarding the next queued vehicle to the toll collection processing
device. The processing device receives this classification
identifier from the inductive loop control microprocessor and
cross-references the classification identifier against a
cross-reference database of identifiers and toll classifications as
defined by the tolling authority. This cross-reference action is
used to assign a particular authority classification and, thus, an
appropriate fare amount expected for the vehicle.
[0166] Since many vehicles with distinct classification identifiers
are of the same general type as it pertains to the local tolling
authority's fare structure, this cross-reference action serves to
reduce the number of distinct vehicle classifications to just those
distinct classifications and associated fare amounts as defined by
the tolling authority. For example, a particular tolling authority
might assign the same general classification to a motorcycle and a
passenger car even though these two vehicles would generate two
distinct classification identifiers or profile information.
[0167] Once the collection processing device has received and
cross-referenced the vehicle data internally, it will communicate
the appropriate classification and fare expected for the vehicle to
the toll attendant if the lane is operating in a manual operational
mode. If the toll lane is operating in an automatic mode, the data
will be used to communicate to any attached automatic toll
collection equipment the expected fare amount that the vehicle
operator must present to gain passage through toll lane 100.
[0168] In order to provide the cross-reference database utilized in
the toll collection processing device, a user program is provided
with the corresponding toll management system. This program allows
the toll authority to select each vehicle type that is distinctly
identified by the loop system microprocessor program and match it
with one of the predefined or predetermined classifications set up
by the authority, which subsequently defines the amount of the fare
expected for that vehicle type.
[0169] The user program can preferably be adapted to employ the use
of digital photographs for each type of vehicle to further
illustrate the exact type of vehicle (or vehicles) which would fall
under each category of vehicles classified by the loop system
microprocessor for visual reference. The authority personnel would
then create the cross-reference table by matching up each loop
microprocessor classification with the corresponding authority
classification. FIGS. 17-20 are exemplary screenshots of such
information.
[0170] Additionally, for vehicles with too many axles to be
classified by the authority's base classification system, the
cross-reference table also allows the user to define the additional
number of axles to add to the base classification axle count to
determine the total fare for such vehicles.
[0171] As the user completes the cross-reference process utilizing
the user program for such purposes, the data is saved to the plaza
system database and subsequently distributed to each toll lane
processing computer for subsequent use in cross-referencing
subsequent vehicles for automatic classification purposes.
[0172] Preferably, intelligent identification unit 270 includes
management software tools. The software tools enable every
transaction (e.g., each vehicle's passing through the toll lane) to
have a complete audit trail. Tracking each transaction increases
the accuracy of the revenue collection process.
[0173] The system shown in FIG. 2 further comprises payment point
290, which is preferably located upstream of toll gate 252, but
downstream of classification loop array 210 in direction 130.
Payment point 290 may be equipped with an automated toll collection
mechanism. Alternatively, payment point 290 may be staffed with a
toll attendant. When an appropriate fare is received at payment
point 290, toll gate 252 opens to allow the vehicle to continue to
move in direction 130. It is noted that other traffic control
apparatus may be used in lieu of toll gate 252. For example,
traffic lights may be used.
[0174] As disclosed above, the capability to charge different toll
fees for different vehicle types at payment point 290 without a
toll attendant is possible with the present invention.
[0175] For convenience, a system of the present invention as shown
in FIG. 2 may be hereinafter referred to as an intelligent vehicle
identification system (IVIS). The IVIS of the present invention can
have a number of embodiments including but not limited to those
shown in FIGS. 2-5.
[0176] The IVIS, as implemented in FIGS. 2-5, combines hardware and
software to identify or classify a vehicle using an arrangement of
inductive loops. The shapes, layout, and number and type of loops
in each of the arrangements can vary depending on how the toll lane
is to be used. For example, different layouts and designs may be
required for slow speed and high speed toll lanes.
[0177] In FIG. 3, for example, classification loop array 300 is
adapted to indicate changes in electromagnetic field which can be
processed to produce profile information of a vehicle that travels
over it in direction 130. The profile information includes initial
signature information, which is produced based at least in part on
data collected by front signature loop 310 and rear signature loop
330, as well as wheel assembly information which is produced based
at least in part on data collected by left wheel assembly loop 320
and right wheel assembly loop 322. One or more of an axle count,
axle spacing, speed, and height of axles from the surface of the
toll lane can be determined using the profile information. The data
collected by the loops is provided to loop detector 260 for
processing. Furthermore, loops 340 and 342 can also be adapted to
indicate changes in electromagnetic field which can be processed to
produce subsequent signature information at locations downstream of
payment point 390.
[0178] Each of the wheel assembly loops 320 and 322 is designed to
detect primarily tires and wheel assemblies of a vehicle. The small
concentrated field width of each of the wheel assembly loops 320
and 322 is obtained by controlling the spacing between the wire
turns. Preferably, the spacing ranges between four and seven
inches. The wheel assembly loops are designed in accordance with
the range of ground clearance present in the vehicle population.
Preferably, the single wire that is used to form each wheel
assembly loop is looped at least twice, thus creating two
overlapping layers of wire for each wheel assembly loop.
[0179] Design of wheel assembly loops 320 and 322 depends on a
number of factors. The factors include characteristics of vehicles
anticipated for the toll lane at which the loop is to be installed.
The characteristics include number of axles, distance between
axles, speed of vehicle through the toll lane, height of chassis
from top of roadway, and other attributes of vehicles detectable by
inductive loops.
[0180] Vehicle separation loops 340 and 342 are designed to be used
to gain additional information on the target vehicle. For example,
vehicle separator loops 340 and 342 can determine the beginning and
end of a vehicle by analyzing the percent in change of inductance.
Also, the magnitude of the percent change in inductance is
proportional to the chassis size and distance from the vehicle
separation loops 340 and 342. In addition, vehicle separation loops
340 and 342 can be used to, as it's name suggests, "separate" each
vehicle one from another.
[0181] The use of vehicle separation loops 340 and 342 provides
vehicle presence, vehicle speed, and chassis length information. A
special signal discriminator is preferably provided with the two
processed signals received from vehicle separation loops 340 and
342. Preferably, the signal discriminator processes this
information and compares the vehicle speed, chassis length, axles,
and chassis height information being collected from vehicle
separation loops 340 and 342. The signal discriminator considers
several factors during this process. For example, the percent in
the change of inductance is used to sense the beginning of a
vehicle and the end of a vehicle. Also, the magnitude of the
percent change in inductance is proportional to the bottom chassis
height and distance from each of the loops. For example, a
motorcycle being followed closely by a car or truck would have a
significant difference in the percent of inductance change. The
movements or speed of the vehicle is also measured on each of these
loops. The movements or speed of the vehicle is determined as a
function of percent change of inductance over time. These two
factors are used to calculate the speed of the vehicle. When the
vehicle is not moving or static the percent change in inductance
becomes constant.
[0182] These constant values for the percent change of inductance
appear as flat horizontal lines when displayed on an inductance vs.
time plot in which the Y-axis represents the percent change in
inductance and the X-axis represents time. A single vehicle or a
vehicle towing another vehicle will normally maintain the same
speed. When two vehicles are following each other in close
proximity, the vehicles typically have somewhat different speeds or
start and stop independently of each other. The signal
discriminator measures these differences to separate the vehicles.
Also the length of the vehicle chassis is calculated to determine
if it is a single vehicle.
[0183] Again, this processor is unique since it performs this
function independently, provides outputs and transfers the
information within the IVIS. This information can be used to
provide volume counts. This process can be used in tolling or other
applications to replace light curtains, optical scanners, video
detectors, and microwave detectors.
[0184] A single vehicle or a vehicle towing another vehicle will
normally maintain the same speed. When two vehicles are following
each other in close proximity, the vehicles typically have
different speeds. Vehicle separation loops 340 and 342 measure
these differences to separate the vehicles. Also, the length of the
vehicle chassis is calculated to verify the existence of one or
multiple vehicles. Accordingly, vehicle separation loops 340 and
342 can be used in the tolling application to replace light
curtains, optical scanners, video detection, and microwave
detectors that are currently in use.
[0185] The loop signal processor and discriminator (LSP&D) unit
preferably has two or more channels of detection that compares the
information processed on a continuous basis to determine when a
vehicle ends and when a new vehicle starts. The end of the vehicle
is used to end the collection of the transaction information. The
LSP&D has the ability to determine the beginning of a vehicle,
the end of a vehicle and distinguish when two vehicles are
traveling in close proximity to each other and/or a vehicle is
towing another vehicle. The LSP&D processes information from
two loops and compares the information to determine if the
information represents a single vehicle or multiple vehicles. When
the end of the vehicle is determined the processor can set a timer
based on the speed of the vehicle.
[0186] In a different arrangement in which loop 342 is an
enforcement loop, as the timer completes its countdown, violation
enforcement camera 370, which is in communication with enforcement
loop 342, receives the signal output to take a picture.
[0187] Enforcement loop 342 is designed to work with camera 370 as
part of a violation enforcement system. If a vehicle leaves
separation loop 340 before the fare is collected at payment point
390, camera 370 takes a photograph of the vehicle when the vehicle
triggers enforcement loop 342. Preferably, camera 370, enforcement
loop 342, vehicle separation loop 340, and payment point 390 are
located such that the photograph would clearly show the license
plate of the vehicle.
[0188] Intelligent vehicle identification unit 270 in one
embodiment of the present invention may be an assembly of
electronic equipment and software that can control other equipment,
store vehicle information, and distribute vehicle information to
other devices or remote locations using an integrated remote
access. Intelligent vehicle identification unit 270 can be adapted
to assemble collected data from classification loop array 300 and
one or more of vehicle separation loops 340 and 342 to create a
composite signature information for the vehicle. One exemplary
composite signature is shown in FIG. 21.
[0189] This collective body of profile information can include tire
information, axle count, axle spacing, chassis height, chassis
length, and vehicle speed. The vehicle record is associated with a
vehicle type or combination vehicle type (i.e., motorcycle, car,
car with trailer) from a database or vehicle library of available
signatures. The database is accessible to intelligent vehicle
identification unit 270. The vehicle type is then placed into a
toll category, defined by the toll authority, to generate the
proper fare for the vehicle. This is then used to drive the toll
system, prompting the toll attendant when using a manual
embodiment, or notifying the driver of the vehicle when using an
automated embodiment, of the proper fare which is due.
[0190] Again, the vehicle types and categories are definable by the
toll authority. Each vehicle type is placed in a category using the
graphical user interface associated with intelligent vehicle
identification unit 270. The graphical interface includes a library
of vehicle types or vehicle combinations using captured digital
images of the local vehicle population. The user interface may be a
local interface, e.g., local interface 272. The user interface may
also be a remote interface, e.g., remote interface 274. The visual
interface allows the assignment of the magnetic and/or inductive
composites of the vehicle records into different categories by
selecting from a menu of captured images. The graphical user
interface is a display of digital images of different vehicle
categories that are used to represent groups of vehicle types. A
group of these categories make up a vehicle library. New vehicle
types can be added to the intelligent vehicle identification unit
by incorporating the captured image and vehicle signature into the
vehicle library. Exemplary screenshots of the vehicle library are
shown as FIGS. 17-20.
[0191] An intelligent vehicle queuing system of the present
invention can be used to insure proper matching of designated toll
amounts to each vehicle. The queuing system profiles the
approaching vehicle at payment point 390 and compares the data with
the profile information held in queue by intelligent vehicle
identification unit 270. If the profile is found to be an incorrect
match, intelligent vehicle identification unit 270 attempts to
properly match the indicated profile with other vehicles waiting in
queue, thus insuring that the profiled vehicle is properly
associated with the system's indicated amount of fare.
[0192] FIG. 4 is a schematic diagram illustrating another
embodiment of the present invention as implemented in a toll road
application. In this embodiment, classification loop array 400
comprises front wheel assembly loop 410, signature loop 420, and
rear wheel assembly loop 412. Furthermore, the embodiment shown in
FIG. 4 comprises intelligent queue loop 430 and enforcement loop
440, payment point 490, rear view camera 470, and front view camera
472. These components are laid out such that rear view camera 470
and front view camera 472 can capture a photograph for vehicle
violation enforcement purposes.
[0193] FIG. 5 is a schematic diagram illustrating another
embodiment of the present invention as implemented in a toll road
application. In this embodiment, classification loop array 500
comprises one or more bi-symmetrical offset wheel assembly loops
510 and 530. Each of the bi-symmetrical offset wheel assembly loops
510 and 530 has a left member and a right member. For example,
front bi-symmetrical offset wheel assembly loop 510 includes left
member 512 and right member 514. Similarly, rear bi-symmetrical
offset 530 comprises left member 532 and right member 534. Each of
the bi-symmetrical offset wheel assembly loops 510 and 530
preferably has a leading edge offset and a trailing edge
offset.
[0194] The offset of the left member and the right member of each
of these bi-symmetrical offset wheel assembly loops is designed to
capture left wheel information and right wheel information at two
different instances in time. A more accurate average speed, axle
separation, and other axle information can be calculated based on
data collected by these bi-symmetrical offset wheel assembly loops
510 and 530.
[0195] As indicated in FIG. 5, classification loop array 500 can
work with additional loops 540 and 542. As used in different
arrangements, one or both additional loops 540 and 542 may be an
intelligent queue loop, a vehicle separation loop, an enforcement
loop, and a gate loop.
[0196] One or more of additional loops 540 and 542 can be adapted
to work with camera 570 and payment point 590. A photograph of a
vehicle can be captured for violation enforcement purposes if an
appropriate fare is not received at payment point 590 when the
vehicle is detected by additional loops 540 and 542.
[0197] FIG. 15 is a diagram showing a view from a payment point
indicating that as vehicle 1520 approaches the payment point that
is associated with toll lane 1500, vehicle 1520 is classified and a
fare is determined and shown on display 1510 without input from a
toll attendant.
[0198] FIG. 16 is a screenshot of display 1510 indicating
classification 1612 for vehicle 1520 and fare 1614, which is
associated with classification 1612. As indicated on FIG. 16,
display 1510 can be adapted to display a number of records
associated with a transaction. Areas 1610 comprises fields
1610-1618. Field 1612 can display the class or category of vehicle
1520 as identified using the profile information of vehicle 1520.
Field 1614 can be used to display the fare associated with the
classification shown in field 1612. In addition, fields 1616 can be
used to display an axle count associated with vehicle 1520. Field
1618 can be used to indicate whether the fare has been received at
a payment point associated with toll lane 1500.
[0199] Area 1620, which comprises fields 1622 through 1632, can be
used to display specifics of the transaction. For example, field
1622 is used to indicate that lane 1500 is Lane No. 3 of the
particular toll plaza. Field 1624 can be used to indicate which
shift of workers is on duty. Fields 1626, 1628 can be used to
display the time and date on which the transaction occurs. Field
1630 can be used, for example, to indicate the status of a toll
gate or other status of the toll lane. Field 1632 can be used to
indicate which, if any, toll attendant is on duty. This information
can be used to increase accountability among toll attendants.
[0200] In some embodiments, field 1640 can be used to manually
operate a toll gate by a toll attendant. In an embodiment in which
a toll attendant is staffed at toll lane 1500, field 1650 can be
adapted to close the transaction after the toll attendant verifies
that the toll has been paid. Field 1660 can be adapted, for
example, to be pressed by the toll attendant in a situation in
which classification made by the IVIS is verified by the toll
attendant. Finally, a toll attendant or an operator of the vehicle
can press a field 1670 to obtain a receipt.
[0201] In FIG. 26, as vehicle 120 travels in direction 130 along
toll lane 100 and passes over classification loop array 2600,
vehicle 120's profile information is collected by intelligent
vehicle identification unit 2670. Intelligent vehicle
identification unit 2670 organizes the raw profile data and
generates a classification for vehicle 120. As vehicle 120 then
passes over the intelligent queue loop 2640, a second set of
profile information is gathered by intelligent vehicle
identification unit 2670. This profile is matched with profiles in
queue generated by the classification loop array 2600. Intelligent
vehicle identification unit 2670 then forwards the proper
classification and/or toll amount to toll system interface 2672 as
the vehicle approaches the payment point.
Overview of the '972 Application [Patent, do we Incorporated by
Reference the '972 Patent so we can Properly Refer to it in these
Paragraphs?]
[0202] Among other things, the present CIP application discloses
additional design and configurations of loops that can be adapted
for use in conjunction with the IVIS disclosed in the '937
application. The present CIP application further provides methods
for installing the loops. The loops associated with the present CIP
application are referred to hereinafter as ferromagnetic loops. It
is noted that the present invention is not limited to vehicles
identification and classification although the preferred
embodiments disclosed herein relate to such purposes.
[0203] In a specific implementation for vehicle detection
applications, the present invention provides a ferromagnetic loop
that is installed on a travel path for detection of vehicles moving
in a direction along the travel path. In the specific
implementation as shown in FIG. 27, ferromagnetic loop 2700 is
characterized by continuous wire 2702, which is shaped in a
serpentine manner within footprint 2704. FIG. 40, which is
described further below, demonstrates the serpentine
characteristics of continuous wire 2702. Footprint 2704 has
footprint length dimension 2706, which is parallel to direction
2710 and footprint width dimension 2708, which is perpendicular to
direction 2710. Continuous wire 2702 forms multiple contiguous
polygons 2712 within footprint 2704. Each of multiple contiguous
polygons 2712 is characterized by polygon length dimension 2716
that is parallel to direction 2710 and polygon width dimension 2718
that is perpendicular to direction 2710. Polygon length dimension
2716 may also be referred to as a spacing dimension. Loop 2700 has
lead-in 2714. Lead-in 2714 connects loop 2700 to loop detector
2720. A frequency associated with ferromagnetic loop 2700 is
affected when a vehicle (not shown) moves across footprint 2704 in
direction 2710. Loop detector 2720 is adapted to output frequency
vs. time plots based on information received from loop 2700.
[0204] In one preferred embodiment, each polygon width dimension
2718 is substantially equal to footprint width dimension 2708 and a
sum of all polygon length dimensions 2716 is substantially equal to
footprint length dimension 2706. In one embodiment, all polygon
length dimensions 2716 are equally long. In a different embodiment,
at least one of polygon length dimensions 2716 is longer than at
least one other polygon length dimension 2716. In other words, the
spacing dimension between any two contiguous polygons may be the
same or vary. For toll road implementation purposes, footprint
length dimension 2706 can range from about 10 inches to about 56
inches. Footprint width dimension 2708 can range from about 24
inches to about 144 inches. Preferably, polygon length dimension
2716 ranges from about three inches to about eight inches.
Preferably, polygon width dimension 2718 ranges from about 24
inches to about 144 inches.
[0205] A ferromagnetic loop of the present invention such as loop
2700 can be adapted to collect a large variety of information
associated with vehicles that move over it. Specifically, the
ferromagnetic loop can, among other things, detect the spacing or
the distance between two successive wheel assemblies of a vehicle,
count the total number of wheel assemblies associated with the
vehicle, calculate the vehicle speed, and determine a category of
the vehicle based on the characteristics of the vehicle. The
ferromagnetic loop is designed to maximize the detection of the
wheel assemblies while minimizing the detection of the vehicle
chassis. As a result of its enhanced capabilities for detection of
wheel assemblies, the ferromagnetic loop can be adapted for use in,
among other applications, traffic law enforcement, toll road
operations, vehicle classification for data collection, and traffic
management. One unique characteristics of the ferromagnetic loop of
the invention is that one single loop can be used to replace the
combination of piezo electric or resistive axle sensors, road tube,
treadles, and multiple figure-of-eight or dipole axle loops that
are currently used to detect wheels and axles.
Review of Various Wheel Sizes
[0206] FIG. 28 is a schematic diagram showing different wheel sizes
of typical vehicles that can be found on the highways. As
illustrated in FIG. 28, the length of the bearing surface of each
wheel (e.g., lengths 2814, 2824, and 2834) is proportional to the
diameter of the wheel. Similarly, the chassis height of the vehicle
(e.g., heights 2812, 2822, 2832) is also proportional to the
diameter of the wheel and the length of bearing surface. Three
typical wheel sizes found in random traffic are illustrated in FIG.
28. Automobile wheel 2810 is smaller than pickup truck wheel 2820,
which is smaller than large truck wheel 2830. Automobile chassis
height 2812 is shorter than pickup truck chassis height 2822, which
is shorter than large truck chassis height 2832. Similarly, bearing
surface length 2814 for automobile is shorter than bearing surface
length 2824 for pickup truck, which is shorter than bearing surface
length 2834 for large truck.
[0207] As shown in Table 1 below, the range for vehicle wheel
diameters as found in random traffic can range from about 12 inches
to about 44 inches in diameter. Typical length of a tire bearing
surface or the length of contact area of a vehicle tire with the
road can range between about 6 inches and about 12.5 inches.
[0208] Table 1 below summarizes selected categories of vehicles and
their associated dimensions.
TABLE-US-00001 TABLE 1 Type of Typical Wheel Typical Chassis
Typical Bearing Vehicle Diameter (inches) Height (inches) Surface
(inches) Trailers 12 to 26 6 6 Motorcycles 12 to 23 6 9 Automobiles
23 to 26 7 8 Pick-ups and 26 to 30 9 9 SUVs Light trucks 30 to 32
12 10 Large trucks 40 to 44 15 12.5
Review of Existing Inductive Loop Technology
[0209] During the development of the ferromagnetic loops of the
present invention, the inventors conducted a series of tests to
evaluate inductive response that are obtainable by existing loop
designs. For example, the inventors evaluated the performance of
the inductive loops disclosed in U.S. Pat. No. 5,614,894 issued to
Daniel Stanczyk on Mar. 25, 1997 (hereinafter "the Stanczyk
patent"). In addition, the inventors evaluated the performance of
the loop designs disclosed in WIPO Publication Nos. WO 00/58926 and
WO 00/58927 (both published on Oct. 5, 2000) (hereinafter "the Lees
applications"). The results of these tests and evaluations are
described below.
[0210] In each of the tests conducted, the same loop detector was
used to measure the results. In other words, no operating changes
was made to the loop detector from test to test. Thus, the only
variable that existed during the tests was the design of each of
the loops being tested. The objective was to understand the
technology disclosed in the Stanczyk patent and the Lees
applications. Specifically, the limitations of these known
technologies for detecting and counting vehicle wheels in random
traffic were evaluated.
[0211] To illustrate the effectiveness of the loop designs
disclosed in the Stanczyk patent and the Lees applications, and to
demonstrate advantages of the present invention, the inductance
changes obtained from each technology were plotted using the same
loop detector. Each of the graphs or plots disclosed herein
represents the changes in the loop circuits as a plot of frequency
on the Y axis and time on the X axis. In other words, each of these
graphs illustrates the effect of a vehicle traveling over a loop in
a traveling lane.
The Stanczyk Patent
[0212] The Stanczyk patent discloses inductive loops having a
rectilinear shape. Loops 2910, 2920, and 2930 shown in FIG. 29
illustrate typical rectangular shapes of this loop geometry. Each
of the rectilinear loops consists of one or several turns of
wire.
[0213] Loop 2910, which has a wider width dimension 2916, can
detect the wheels from the left and right sides of a vehicle
traveling on roadway 2902 in direction 2904. Loops 2920 and 2930
(each having a narrower width 2926) are designed to detect
separately the left wheels and the right wheels of the vehicle. The
Stanczyk design uses an ideal loop length 2908 of 0.3 meter (11.81
inches) for heavy vehicles and 0.15 meter (5.91 inches) for light
vehicles. Each of these loop length dimensions is shorter than the
bearing surface length of the vehicle wheels to be detected. This
design provides a short travel time as wheels move through the
inductive field of the loop, and it limits the sample size
available for the wheel detection. Dimension 2908 affects the field
height of the loop circuit. If dimension 2908 of this loop design
is increased to a size larger than the diameter of the wheels it is
designed to detect the field height of the loop detection is also
increased. This is a limitation to the Stanczyk patent because when
length dimension 2908 is increased, a stronger detection of the
vehicle chassis is resulted, which inhibits the detection of
wheels.
[0214] Therefore, the loop disclosed in the Stancyzk patent is
limited by its geometric design since its performance is dependent
on the bearing surface of the wheel of the vehicles being detected.
In random traffic, vehicles have wheels that range from 12 inches
to 40 inches in diameter with bearing surface widths ranging from
six to 12.75 inches. To properly detect all the different vehicle
wheel sizes in random traffic, multiple rectilinear loops of the
Stancyzk patent would be required in the roadway. In other words,
multiple loops each with a different length dimensions 2908 would
be required to provide wheel detection for all vehicles that exist
in random traffic. Using the technology disclosed in the Stancyzk
patent, a single loop size will not work on both large wheeled
trucks and smaller wheeled vehicles. For example, when a loop that
has a specific length dimension 2908, which is designed to detect a
tire bearing surface of 12 inches, the loop cannot be used to
detect tires with a bearing surface of 7.5 inches long.
[0215] FIGS. 29A-29C are frequency vs. time plots obtained from the
use of a rectangular loop in accordance with the teaching of the
Stanczyk patent. The rectangular loop that was used to generate
plot 2942 shown in FIG. 29A was 10 feet wide by 10 inches long and
it had two turns. When a car with a tire diameter larger than 10
inches traveled over this loop, eddy currents created by the car
chassis were detected by the loop. As shown on plot 2942 in FIG.
29A, it was impossible to determine the presence of wheel
assemblies of the car due to strong detection of the chassis.
[0216] Similarly, plot 2944 shown in FIG. 29B illustrates the
detection of a pickup truck (with a tire diameter of 26 inches)
traveling over the same loop. Again, the detection of the vehicle
wheels was impossible because the eddy currents created by the
chassis could not be separated. This explains why the length of the
loop circuit, or dimension 1 as shown in FIG. 1 of the Stanczyk
patent must be smaller than the diameter of the wheel being
detected. (See Stanczyk patent, Abstract and col. 2, lines 61-64.)
This is because when the length of the loop (dimension 2908 shown
in FIG. 29 of the present invention or dimension 1 shown in FIG. 1
of the Stanczyk patent) is increased to a size larger than the
diameter of the wheel being detected, the loop senses the chassis
of the vehicle, making it impractical to be used as a sensor for
counting wheels. Plot 2946 shown in FIG. 29C further illustrates
this observation as a vehicle having a wheel diameter of 24 inches
was detected using a loop 10 feet wide by 20 inches long. As
indicated in FIG. 29C, wheel assemblies of the vehicle were not
discernable on plot 2946 even though the loop length has not
exceeded the wheel diameter of 24 inches.
[0217] Plot 2948 shown in FIG. 29D demonstrates that vehicle wheels
can be detected if the loop length (dimension 2908) is
significantly shorter than vehicle wheel diameter. In FIG. 29D, the
rectangular loop was 10 feet by 20 inches and the pickup truck had
a wheel diameter of 29.5 inches. The tire bearing lengths for the
rear and front wheels were 9.75 inches and 10.25 inches,
respectively. As shown in FIG. 29D, the front and rear wheel
assemblies are discernable from plot 2948 because the frequency
fluctuation associated with the wheels on the pickup truck can be
distinguished from the frequency associated with the chassis eddy
currents. Plot 2950 shown in FIG. 29E illustrates a parcel delivery
truck (with a wheel diameter of 30 inches) traveling over a loop 10
feet wide by 20 inches long. Even though the wheel assemblies were
detected, the eddy currents from the chassis were also detected.
Thus, while the loop was suitable to detect a smaller wheel, it can
not be used to detect larger wheels without also detecting the
vehicle chassis of the vehicle with large wheels. Therefore, FIGS.
29D and 29E indicate that more than one loop size would be required
to detect the various wheels sizes found in random traffic.
[0218] Accordingly, the rectilinear design of the Stanczyk patent
has geometric constraints that limit the size of sample or sensing
area. This limits the sample length of the each wheel and prevents
the ability to accurately measure the speed of the vehicle. When
the length of the loop is increased, the field height increases and
eddy currents also increase making this design not practical to
calculate wheel speed on a single loop. As indicated in the
Abstract and in at least Col. 2, lines 61-64, the Stanczyk patent
specifically teaches that the length of the loop must be smaller
than the diameter of the wheel. The preferred length of the loop
tends to be limited to the bearing length of the tire, or the tire
bearing lengths tend to be longer than the loop length, to provide
distinct wheel detection.
[0219] In addition, the rectangular design of the Stanczyk patent
uses multiple turns of wire around the perimeter, and the design is
limited to a length that is shorter than the diameter of the wheel
it is detecting. As the length of the loop is made small, the loop
would detect smaller vehicles but not larger ones.
[0220] In contrast to the Stanczyk patent, as explained below, the
ferromagnetic loop of the present invention offers greater
flexibility in size and shape of the loop geometry and provides a
longer travel area for the wheel paths. As explained below, a
single ferromagnetic loop of the present invention is capable of
detecting different size wheels found in random traffic.
Significantly, the length of a ferromagnetic loop of the present
invention can be greater than the diameter of the wheel being
detected. Thus, it is possible to use a single ferromagnetic loop
of the present invention to detect the entire population of wheels
in random traffic. The loop can also detect the difference between
single-tire and dual-tire assemblies. Also, the longer loop sample
time associated with the ferromagnetic loop provides the ability to
calculate speed using just a single loop.
The Lees Applications
[0221] The figure-of-eight loop design (also referred to
hereinafter as the dipole loop design) disclosed in the Lees
applications has a central winding, with the two outer segments in
the direction of travel having a length shorter than about 23.6
inches (or about 60 cm), and preferably about 17.7 inches (or about
45 cm). FIG. 30 illustrates the typical loop geometry in accordance
with the Lees applications. Loop 3010 illustrates the use of a
single loop to detect both left and right wheels of the vehicle.
Loop 3010 has front segment 3011 and rear segment 3012. Loops 3020
and 3030 are used to separately detect the left wheels and the
right wheels, respectively. Each of loops 3020 and 3030 also has
front and a rear segments.
[0222] A figure-of-eight loop similar to loop 3010 with dimensions
10 feet wide by 18 inches long (i.e., each front segment 3011 and
rear segment 3012 is nine inches long), built and installed in
accordance with the Lees applications, was used for evaluation
purposes by the inventors. Plot 3042 shown in FIG. 30A is a
frequency versus time plot that was obtained during the detection
of a car traveling over the loop. As shown on plot 3042, the
detection of wheels was not well defined. The same loop was used to
detect the wheels on a pickup truck with a larger wheel diameter.
As indicated by plot 3044 shown in FIG. 30B, a loop of this size
provided improved wheel detection on the larger size wheels. As
indicated by plot 3046 shown in FIG. 30C, this loop size also
provided good wheel detection on truck wheels having a diameter of
30 inches. The truck associated with FIG. 30C had dual wheel
assemblies on the rear axle. The 10 feet wide by 18 inches long
loop detected the wheels on the truck but does not reflect any
difference in amplitude from the front to the rear dual tires.
[0223] For the dipole (figure-of-eight shape) loop with the
dimensions of 10 feet by 18 inches, the test results indicated that
it is not suitable for detection of small-wheeled vehicles. The
wheels are not clearly defined in plots generated by this loop
because the chassis of vehicles with small wheels lowers the
frequency of the loop circuit.
[0224] As further explained below, the ferromagnetic loop of the
present invention is different from the loops disclosed in the Lees
applications since the geometry allows the loop's length to be
longer than the diameter of the wheel to be detected. Furthermore,
a single loop design can detect the different wheel sizes. It
should be noted that the design of the present invention also has
the ability to detect dual wheels. The amplitude of the front wheel
can be compared to the rear wheel to determine the presence of dual
tires on the rear axle using the ferromagnetic design of the
present invention.
[0225] Plot 3048 shown in FIG. 30D shows the detection of a car
traveling over a five feet wide by 18 inches long dipole loop
(e.g., loop 3020). As shown in FIG. 30D, wheels of the car were not
properly detected using a loop of this size. Plot 3050 shown in
FIG. 30E shows that a five feet wide by nine inches long loop was
able to detect the same wheels that were not detected in FIG. 30D.
FIGS. 30D and 30E demonstrate that different lengths of the dipole
loop were required to detect different wheel sizes.
[0226] FIG. 30F illustrates the use of inductive loops with a "coil
within a coil" design. The design includes a left pair of loops
3070 and a right pair of loops 3080 to count wheels. Each pair of
loops 3070 and 3080 includes a smaller dipole loop nine inches long
(dimension 3067) and approximately five feet wide (dimension 3066)
and a larger dipole loop 18 inches long (dimension 3068) and
approximately five feet wide (dimension 3066). A total of four
wheel loops were used per lane and therefore four lead-ins 3040 are
indicated. When each loop used in this wheel detection design was
examined on an individual basis, the results indicated that the
smaller loop nine inch long detected small wheels of cars and the
larger loop 18 inches long detected larger wheels.
[0227] For the smaller dipole loop with the dimensions of nine
inches by five feet, the test results revealed that this loop
design has a low field height with a stronger field in the center
of the loop. Thus, the ability to detect wheels on vehicles was
biased to small vehicle wheels, which are normally found on cars
and small trailers. Accordingly, this loop design does not detect
the wheels of vehicles with larger diameters, such as those found
in pickup trucks, small trucks, and other larger vehicles.
[0228] For the larger dipole loop with the dimensions of 18 inches
by five feet, the test results revealed that this loop design has a
slightly higher field height with a stronger field in the center of
the loop. The detection of wheels on small vehicles (e.g., cars)
was not very clear, however, because the higher field found in this
loop design was influenced by the chassis of the vehicle. This
influence caused the frequency of the loop circuit to be lowered.
The wheels were not clearly defined since the chassis effect and
the wheel effect tend to cancel each other out. However, this
design does provide better detection of vehicles that have larger
wheels and more ground clearance.
[0229] Thus, the "coil within a coil" design (i.e., a smaller loop
with dimension 3067 located within a larger loop with dimension
3068) as referenced in the Lees applications relies on two separate
loop sizes to detect smaller and larger wheels. The use of four
loops per lane is designed to detect the entire vehicle population,
but the arrangement is dependent on both the nine and 18 inches
long dipole loop design to detect the different sizes of the wheels
found in the vehicle population. Also, these designs have a smaller
dimension in the direction of travel than the wheel diameters. This
provides a short signal sample rate from the wheels.
[0230] In contrast, and as explained below, the ferromagnetic loop
of the present invention requires only a single loop to detect all
the different wheel sizes that exist in random traffic. The
ferromagnetic loop design also has the ability to provide wheel
detection and vehicle speed on the same loop.
Ferromagnetic Loops of the Present Invention
[0231] Various configurations and designs of the ferromagnetic
loops disclosed herein can be used for difference purposes. One
exemplary purpose of the preferred embodiments of the invention, as
described below, is to detect, identify, and classify vehicles. In
the preferred embodiments, the ferromagnetic loop is adapted to
communicate with a signal-processing device (e.g., a loop detector)
to generate an electromagnetic field in a traveling path of a
vehicle, measure the changes in frequency and inductance associated
with the vehicle passing over the ferromagnetic loop, and output
the results. The results can be used to determine, among other
things, various characteristics of the vehicle including, for
example, number of axles, distances between axles, and speed.
[0232] A preferred embodiment of the ferromagnetic loop has a
unique loop geometry that provides a flux field. The loop circuit
and geometry creates a flux field that responds to the
ferromagnetic loop effect of wheel assemblies on vehicles. This
ferromagnetic effect results in an inductance increase and
frequency increase that can be detected by a loop signal-processing
device (e.g., loop detector 260 shown in FIG. 2) in communication
with the ferromagnetic loop. The changes in inductance and
frequency can be quantified and used for characterization of
vehicles.
[0233] Key elements of the ferromagnetic loops of the invention
include the magnetic strength of the flux field height and length.
The shallow installation of the wire and wire orientation of the
coil in permanent and temporary installations is very important for
optimal performance of the ferromagnetic loop design. The flux
field created by the loop circuit is concentrated and low to the
road surface to maximize the ferromagnetic effect of the wheel
assemblies and minimize the eddy currents created by vehicle
chassis.
[0234] The increase in inductance is detected by the ferromagnetic
loop and the information can be used to count wheel assemblies. The
ferromagnetic effect occurs when a ferrous object is inserted into
the field of an inductor and reduces the reluctance of the flux
path and therefore, increases the net inductance and frequency.
This loop design and geometry responds to the wheel assemblies in
this manner.
[0235] The geometry of the loop wire turnings can be oriented in
different directions relative to the direction that vehicles travel
in order to vary the response of the loop sensor to the vehicle
wheels. The geometry and orientation of the loop wires can be
designed to minimize ground resistance. For example, as the
presence of reinforcing steel (a ferrous material) affects the
magnetic field of the loop, the orientation of the lines of flux
created by the loop geometry can be changed to minimize the
environmental influences of the reinforcing steel. This is
reflected in the wire turnings that are diagonal to the travel
direction of the vehicle and diagonal to the typical orientation of
reinforcing steel used in pavement design. This is an important
design feature since it can help to reduce the magnetic influence
that reinforcing steel has on the lines of flux created by the loop
and improve the loops circuit response to wheels assemblies.
[0236] The ferromagnetic loops as disclosed herein provides a
number of improvements over existing inductive loops. For example,
the ferromagnetic loops can be made to have various unique
geometric shapes and coil spacing (of the wire used in the wire
turnings) to obtain a desirable flux field. Preferred embodiments
of the ferromagnetic loops of the invention include the following
characteristics:
[0237] A unique design of molded loops that incorporates a locking
mechanism or an anchor to secure the loops in permanent
installations.
[0238] A design of a single loop that has the ability to detect
vehicle wheel assemblies and provide the distinction between single
tire assemblies, dual tire assemblies, and grouped axles.
[0239] A design that is capable of providing wheel speed, vehicle
speed, axle spacing, number of axles, and vehicle classification
with a single loop.
[0240] A unique sensor arrangement and sensor spacing using two
ferromagnetic loops that pairs two axle vehicles together by
providing loop detections on both loops at the same time or in
extremely close proximity of each other therefore greatly
simplifying the vehicle classification process in congested
traffic.
DISCLOSURE OF PREFERRED EMBODIMENTS
[0241] FIG. 31 is a schematic diagram illustrating a layout of two
ferromagnetic loops of the invention. Path 3102 is a roadway on
which vehicles travel in direction 3104. Path 3102 may be a toll
lane, a driveway, the entrance to a parking garage, a
high-occupancy (HOV) lane, and the like. Gradient diagonal loop
3110 and regular diagonal loop 3120 are located on path 3102 in
such a way that one or more of the wheel assemblies of a vehicle
will pass over loops 3110 and 3120 when traveling on path 3102 in
direction 3104. Although shown together in FIG. 31, only one of
loops 3110 and 3120 is sufficient to implement the invention.
[0242] In this embodiment, each of loops 3110 and 3120 has wire
turnings that are oriented in a diagonal manner relative to
direction 3104. Note that each of polygonal axis 3111 and polygonal
axis 3121 forms angle A with direction 3104. In other words, the
contiguous polygons confined with a footprint of the loop form
angle A with the direction. Angle A can range between zero and 90
degrees. Specifically, angle A can be, for example, 30 degrees, 45
degrees, or 60 degrees. The diagonal orientation of the wire
turnings helps null or minimize the environmental influences that
reinforcing steel has on the lines of flux (to the extent that the
reinforcing steel are present and embedded within path 3102).
[0243] Note that gradient diagonal loop 3110 and regular diagonal
ferromagnetic loop 3120 have different loop configurations. Regular
diagonal loop 3120 has uniform spacing dimensions 3124 between wire
turnings. In other words, the parallel diagonal lines within the
footprint of loop 3120 have the same distance from each other. This
uniform loop spacing provides detection in random traffic but can
be designed for detection of specific wheel sizes. For example, the
spacing can be one that which is optimum to detect the presence of
a tractor-trailer in a traffic lane in which tractor-trailers are
prohibited. Gradient diagonal loop 3110 is characterized by varying
spacing dimension 3114, which are represented by different widths
of spacing between the parallel diagonal lines within the footprint
of loop 3110. The different spacing used in loop 3110 improves the
loop circuit field by increasing the sensing range from small to
large wheels on a single ferromagnetic loop design. The shorter or
narrow sections detect small wheel assemblies and the longer or
wider sections detect larger wheels. The gradient loop
configuration is suitable for detecting a wide range of vehicle
categories. Preferably, spacing dimensions 3114 and 3124 ranges
between about three inches and about eight inches.
[0244] Loops 3110 and 3120 are associated with lead-ins 3112 and
3122, respectively. Lead-ins 3112 and 3122 are in communication
with one or more loop detector, a device previously disclosed in
the '937 application (e.g., detector 260 shown in FIG. 2).
[0245] FIG. 31A is a schematic diagram illustrating gradient
diagonal loop 3110 in greater details. As shown in FIG. 31A, loop
3110 has width W. A typical dimension for width W is about 10 feet.
Width W can vary depending on specific applications. Leading edge
3114 and trailing edge 3116 are separated by length L. A typical
length L is about 32 inches. Depending on specific applications,
the separation between leading edge 3114 and trailing edge 3116
(i.e., length L) can vary. For example, distance L can be longer or
shorter than 32 inches.
[0246] In the specific embodiment shown in FIG. 31A, wire turnings
3118 (the diagonal lines within the footprint of loop 3110) are
parallel, and each of wire turnings 3118 forms an angle A with
respect to leading edge 3114 and trailing edge 3116. Angle A can
range between zero and 90 degrees. For example, angle A can be
about 30 degrees. In addition, wire turnings 3118 have at least two
spacings. Wider spacings 3111 can be about seven inches wide
between two adjacent wire turnings 3118. The spacing is suitable
for detection of larger vehicles such as buses, large trucks and
the like. Narrower spacing 3113 can be about 3.5 inches wide
between two adjacent wire turnings 3118. This spacing is suitable
for smaller vehicles such as trailers, small cars, SUV, pick up
trucks, and the like.
[0247] FIG. 31B is a schematic diagram showing the unique
installation of the wire coils. Wire turnings 3118 are installed in
slots 3130 in path 3102. Slots 3130 can be about 0.5 to about 0.75
inches wide and about one inch deep. Note that wire turnings 3118
are installed parallel to the surface of path 3102 and laid
side-by-side with each slot 3130 (see also FIG. 41).
[0248] FIG. 32 is a schematic diagram illustrating another
embodiment of the invention. This layout is preferable in locations
that require a wider detection area. For example, this layout is
desirable if traveling path 3202 is greater than 11 feet wide. As
shown in FIG. 32, each of ferromagnetic loops 3210 and 3220
contains more than one portion or segment. For example, left
ferromagnetic loop 3210 includes right segment 3212 and left
segment 3214. Similarly, right ferromagnetic loop 3220 includes
right segment 3222 and left segment 3224. This design provides a
wider area of detection without using additional wire in central
regions 3213 and 3223. This two-segment design provides detection
in two wheel paths. In other words, each of right segments 3212 and
3222 detects the right wheels of a vehicle traveling in direction
3204. Similarly, each of left segments 3214 and 3224 detects the
left wheels of the vehicle traveling in direction 3204.
[0249] The ferromagnetic loop is designed to detect primarily the
wheel assemblies by providing an increase in the frequency and
inductance of the loop circuit thereby maximizing the ferromagnetic
effect. The design provides detection of the entire range of wheel
sizes illustrated in FIG. 28 using a single loop circuit. The loop
is designed to have a low field height that minimizes the eddy
currents created by the chassis traveling through the coils field
of flux.
[0250] The ferromagnetic effect of the present invention is
illustrated in frequency vs. time plots shown in FIGS. 33, 33A, 34,
35, 36, 37, and 38. It is noted that these plots and subsequent
plots disclosed herein were produced using the same
signal-processing device that was used to generate the plots shown
in FIGS. 29A, 29B, 29C, 29D, 29E, 30A, 30B, 30C, 30D, and 30E. No
adjustments were made to the signal-processing device for
generating the plot shown in FIG. 33 and the subsequent plots,
which are described in Example Numbers 1 through 46 below. The only
variable was the loop circuit and the geometry of the loop circuit.
The scale for each of these plots is 5.5 milliseconds per point on
the time or X-axis. The Y-axis represents the resonant frequency
(in Hertz) of the loop circuit. The information presented in each
of these plots was provided as a serial output using a sample time
of 5.5 milliseconds. The information can also be made available as
a discrete output from the signal-processing unit to be processed
to count wheel assemblies.
Example No. 1
[0251] Plot 3300 shown in FIG. 33 illustrates the detection of an
automobile. The time that the front wheels of the automobile were
detected occurred between point 3302 (where x1=228 and y1=80078)
and point 3304 (where x2=274 and y2=80104) on plot 3300. This
represented a detection sample length that was 253 milliseconds
long (i.e., (x2-x1) multiplied by 5.5) and a change in frequency of
26 hertz (i.e., y2-y1). The time that the rear wheels of the car
were detected occurred between point 3306 where x3=348 and point
3308 where x4=390 on plot 3300. This represented a sample length of
227 milliseconds and a frequency change of 33 hertz. [can't find
any reference to this being changed in a previous application].
Example No. 2
[0252] Plot 3310 shown in FIG. 33A demonstrates the detection of a
smaller car with a lower ground clearance that passed over the same
ferromagnetic loop discussed in Example No. 1. As shown on plot
3310, the first wheel was detected between points where x1=830 and
x2=928, with a sample length of 539 milliseconds and a frequency
change of 35 hertz. The second wheel was detected between points
where x3=1214 and x4=1317, with a sample length of 566 milliseconds
and a frequency change of 38 Hertz. The eddy currents created from
the chassis were detected between points where x2=928 and x3=1214,
which had the opposite effect, which lowered the frequency by 23
hertz.
Example No. 3
[0253] Plot 3400 shown in FIG. 34 demonstrates the detection of the
wheel assemblies of a pickup truck traveling at 10 mph over the
same loop. The front wheel assemblies were detected at the between
points where x1=1795 and x2=1850. This represented a sample length
of 303 milliseconds for the front wheel assembly. The rear wheel
assemblies were detected at the time between points where x3=1954
and x4=2011. This represented a sample length of 314 milliseconds
for the rear wheel assembly.
[0254] In plots shown in FIGS. 35-38, the ferromagnetic loop used
to detect the vehicle was 10 feet wide by 28 inches long. The
ferromagnetic loop used had diagonal turnings with equal spacing.
Information associated with the vehicle was collected by the
ferromagnetic loop after the vehicle stopped prior to traveling
over the loop and then proceeded to move over the loop. During the
vehicle detection period, the acceleration of the vehicle was
reflected in the decreasing sample lengths of the wheel detections.
The sample length and loop geometry provided vehicle speed on the
basis of the length of the loop and the length of the sample.
Example No. 4
[0255] Plot 3500 shown in FIG. 35 demonstrates the detection of a
two-axle truck. Plot 35 shows that the front set of wheels of the
two-axle track were detected between points where x1=1818 and
x2=1883, a sample length of 358 milliseconds. The rear set of
wheels were detected between points where x3=2036 and x4=2082, a
sample length of 253 milliseconds. This vehicle was detected while
accelerating and that is why the sample lengths are different. The
shorter sample time indicates the rear of the vehicle was traveling
faster over the loop than the front wheel assembly did. This
vehicle also had dual wheel assemblies (i.e., two tires per wheel
hub) on the rear axle. This is indicated by the difference in the
frequency change when comparing the front frequency change of 89
Hertz and the rear frequency change of 198 Hertz.
Example No. 5
[0256] Plot 3600 shown in FIG. 36 demonstrates the detection of a
three-axle truck. The front wheels were detected between points
where x1=882 and x2=966 with a sample length of 366 milliseconds.
The second set of wheels were detected between points where x3=1129
and x4=1185 with a sample length of 308 milliseconds. The third set
of wheels were detected between points where x5=1191 and x6=1245
with a sample length of 297 milliseconds. This vehicle was detected
while accelerating and that is why the sample lengths are
different. The short sample time indicates the rear of the vehicle
was traveling faster over the loop than the front wheel assembly
did. This vehicle also had dual wheel assemblies on the rear two
axles, which is indicated by the difference in the frequency change
when comparing the front frequency change of 178 Hertz, second
frequency change 418 Hertz, and the third frequency change of 597
Hertz.
Example No. 6
[0257] Plot 3700 shown in FIG. 37 demonstrates the detection of a
five-axle truck. The front set of wheels was detected between
points where x1=1531 and x2=1593 with a sample length of 341
milliseconds and frequency change of 139 Hertz. The second set of
wheels was detected between points where x3=1766 and x4=1817 with a
sample length of 281 milliseconds and a frequency change of 172
Hertz. The third set of wheels was detected between points where
x5=1827 and x6=1876 with a sample length of 270 milliseconds and a
frequency change of 216 Hertz. The fourth set of wheels was
detected between points where x7=2016 and x8=2059 with a sample
length of 172 milliseconds and a frequency change of 254 Hertz. The
fifth set of wheels was detected between points where x9=2059 and
x10=2095 with a sample length of 198 milliseconds and a frequency
change of 209 Hertz. This vehicle was detected while accelerating
and that is why the sample lengths are different. The short sample
time indicates the rear of the vehicle was traveling faster over
the loop then the front wheel assembly. This vehicle also had dual
wheel assemblies on the second through fifth sets of wheels, which
is indicated by the difference in the frequency changes.
Example No. 7
[0258] Plot 3800 shown in FIG. 38, demonstrates the detection of a
six-axle truck. The front set of wheels detected from points where
x1=73 and x2=158 with a sample length of 468 milliseconds and
frequency change of 218 Hertz. The second set of wheels was
detected between points where x3=346 and x4=404 with a sample
length of 319 milliseconds and a frequency change of 327 Hertz. The
third set of wheels was detected between points where x5=411 and
x6=479 with a sample length of 374 milliseconds and a frequency
change of 290 Hertz. The fourth set of wheels was detected between
points where x7=894 and x8=954 with a sample length of 330
milliseconds and a frequency change of 418 Hertz. The fifth set of
wheels was detected between points where x9=961 and x10=1018 with a
sample length of 314 milliseconds and a frequency change of 121
Hertz. The sixth set of wheels was detected between points where
x11=1022 and x12=1079 with a sample length of 314 milliseconds and
a frequency change of 317 Hertz. This vehicle was detected while
accelerating and that is why the sample lengths are different. The
short sample time indicates the rear of the vehicle was traveling
faster over the loop than the front wheel assembly.
[0259] The wire turnings in this ferromagnetic design can also be
oriented parallel or perpendicular to the travel direction of
traffic. The perpendicular orientation is illustrated in the
typical ferromagnetic loop geometry shown in FIG. 39. Loop 3910
shows gradient characteristics having contiguous polygons of
different coil lengths. The shorter coil lengths (preferably 3.5
inches) within longer lengths (preferably 7 inches) provide good
flux field density for wheel detection. These dimensions are
designed specifically for the range of wheel sizes found in random
traffic. These dimensions can be adjusted to change the field
height of the loop. This unique geometry and method of wire
turnings is illustrated in FIG. 40, in which arrows 4002 indicate
directions of wire turnings.
[0260] As shown in FIG. 40, the wire is installed in a serpentine
manner as indicated by arrows 4002. Preferably, there are at least
two complete turns as indicated by a solid line and a dashed line.
A cross section of the loop along line A-A is shown in FIG. 41,
which indicates the two turns. As indicated in FIG. 41, the wire
turnings in each slot 4106 are preferably laid side by side. The
spacing illustrated includes coils 3.5 inches and 7 inches long.
This provides a unique flux field that can detect a wider range of
wheel sizes than a single spacing can. This loop has a field height
that provides an even field strength and has the ability to detect
small vehicle wheels like those found on trailers as well as larger
wheels such as those found on pickup trucks and larger
vehicles.
[0261] The preferred method of installation involves installing the
wire within one inch of the road surface. In other words, depth
4108 is preferably about one inch. It is also preferable to install
the wire turnings parallel to the road surface (i.e., wire turnings
4102 and 4104 are side-by-side as shown in FIG. 41) and not
perpendicular to the road surface (i.e., wire turnings 4202 are on
top of wire turnings 4204 as shown in FIG. 42). A saw cut 3/4
inches wide is preferable for slots 4106. The serpentine method
used to make the wire turnings helps keep the wire turnings
horizontal to the road and in close proximity to the wheels being
detected. FIG. 42 illustrates the ferromagnetic loop being
installed in a typical saw cut 4206 used for an inductive loop
(note that one wire turning is on top of the other wire turning).
The performance of the loop design shown in FIG. 42 will not
provide the maximum desired wheel detection when the loop design is
installed using conventional loop installation saw depths of 11/2
to 2 inches deep. In FIG. 42, the cross-sectional view shows the
results of using a conventional saw cut 0.125 inches wide instead
of the preferred 0.75 inches wide.
[0262] The number of wire turnings can be increased in the gradient
in order to increase the detection response of smaller or larger
wheels by increasing the number of wire turns in a particular
spacing. This increases the field of flux at the appropriate level.
This is illustrated in FIG. 43, which shows two or more wire
turnings in slots 4106 with 7 inch spacing for the detection of
larger wheels and dual wheel assemblies. Plots shown in FIGS.
43A-43D demonstrate the detection of vehicles using the gradient
loop design shown in FIG. 43.
Example No. 8
[0263] Plot 4310 shown in FIG. 43A demonstrates the detection of a
car using a gradient loop 10 feet wide by 31.5 inches long. The
approximate wheel diameter on the car was 24 inches. The first tire
was detected between points where x1=1643 and x2=1750. The second
wheel was detected between points where x3=1902 and x4=1999.
Example No. 9
[0264] Plot 4320 shown in FIG. 43B illustrates the detection of the
wheels of a pickup truck with dual tire assemblies on the second
axle using the gradient loop 10 feet wide by 31.5 inches long. The
approximate wheel diameter on this vehicle was 29 inches. The first
tire was detected between points where x1=568 and x2=682. The
second wheel was detected between points where x3=994 and x4=1153.
The amplitude for the first wheel was 96 hertz and the amplitude
for the second wheel was 152 hertz. The second wheel detection was
greater because of the presence of the dual tire assembly.
Example No. 10
[0265] Plot 4330 shown in FIG. 43C illustrates the detection of the
wheels of a pickup truck towing a trailer having two axles. The
wheel assemblies were detected using the gradient loop 10 feet wide
by 31.5 inches long. The approximate wheel diameter on the truck
was 29 inches and the trailer wheels were 12 inches in diameter.
The first tire was detected between points where x1=2206 and
x2=2525. The second wheel was detected between points where x3=3210
and x4=3641. The trailer wheels were detected between points where
x5=4795 and x6=4922 and between points where x7=4922 and
x8=5067.
Example No. 11
[0266] Plot 4340 shown in FIG. 43D illustrates the detection of a
pickup truck towing a trailer having one axle. The wheel assemblies
were detected using the gradient loop 10 feet wide by 31.5 inches
long. The approximate wheel diameter on the truck was 29 inches and
the trailer wheels were 12 inches in diameter. The first tire was
detected between points where x1=331 and x2=412. The second wheel
was detected between points where x3=592 and x4=663 and the trailer
wheel was detected between points where x5=832 and x6=876.
[0267] Referring back to FIG. 39, note that loop 3920 has equal
spacing. The cross-sectional view of loop 3920 is illustrated in
FIG. 44. Plots shown in FIGS. 44A to 44E show vehicles being
detected on ferromagnetic loop that is 28 inches long and 56 inches
wide.
[0268] The longer loop length can be used to detect grouped axles.
Vehicles having two or more axles with a spacing shorter than the
loop length can be easily detected on a single loop. The detection
of grouped axles results in distinct patterns of detection that is
directly related to the axle spacing of the group of axles. The
pattern includes such parameters as the number of peaks, amplitude
of the peaks, lengths of the peaks, and speed of the wheels.
Example No. 12
[0269] Plot 4410 shown in FIG. 44A illustrates the detection of a
car having two axles using a loop 10 feet wide by 56 inches long
having coils with 7 inches of spacing. The approximate wheel
diameter on the car was 24 inches. The first wheel was detected
between points where x1=656 and x2=726. The second wheel was
detected between points where x3=776 and x4=843.
Example No. 13
[0270] Plot 4420 shown in FIG. 44B illustrates the detection of a
truck having two axles using a loop 10 feet wide by 56 inches long
having coils with 7 inches of spacing. The approximate wheel
diameter on a truck was 40 inches. The first wheel was detected
between points where x1=327 and x2=440. The second wheel was
detected between points where x3=553 and x4=652. Note that in slow
speed conditions the wheel detection contains small peaks that
occurred during the wheel detection. The time indicated between two
small peaks represents seven inches of wheel travel. This
demonstrates the ability of this unique loop geometry to obtain
wheel speed information.
Example No. 14
[0271] Plot 4430 shown in FIG. 44C illustrates the detection of a
truck having two axles and dual tires on the second axle using a
loop 10 feet wide by 56 inches long having coils with 7 inches of
spacing. The approximate wheel diameter on the truck was 40 inches.
The first wheel was detected between points where x1=325 and
x2=440. The second wheel was detected between points where x3=555
and x4=649. The amplitude of the first wheel detection was 75 hertz
and the amplitude of the second dual wheel detection was 134 hertz.
Note that in slow speed conditions the wheel detection contains six
small peaks that occurred during the wheel detection. These small
peaks represent a seven inches of wheel travel between the peaks.
This demonstrates the ability of this unique loop geometry to
obtain wheel speed information.
Example No. 15
[0272] Plot 4440 shown in FIG. 44D illustrates the detection of a
pickup truck having two axles with dual wheels on the second axle
and towing a two-axle trailer using a loop 10 feet wide by 56
inches long having coils with 7 inches of spacing. The approximate
wheel diameter on a truck was 29 inches. The first wheel was
detected between points where x1=475 and x2=563. The second dual
wheel was detected between points where x3=659 and x4=727. The
third wheel was detected between points where x5=795 and x6=835.
The fourth wheel was detected between points where x7=835 and
x8=876. The amplitude for the first wheel detection was 84 hertz
and the amplitude for the second wheel detection was 178 hertz. The
wheels of the trailer with two axles were detected between points
where x9=795 and x10=835 and between points where x11=835 and
x12=876. The wheels being detected at point where x11=835 had an
amplitude of 134 hertz. In contrast, the amplitude for the leading
edge of the first wheel was 74 hertz and the trailing edge for the
second wheel was 78 hertz. The higher amplitude at point where
x11=835 is due to the presence of the four trailer wheels on the
loop at the same time. The detection of this axle group provides a
distinct pattern of detection.
Example No. 16
[0273] Plot 4450 shown in FIG. 44E illustrates the detection of a
truck having four axles using a loop 10 feet wide by 56 inches long
having coils with 7 inches of spacing. The approximate wheel
diameter on a truck was 39 inches. The first wheel was detected
between points where x1=448 and x2=571. The second wheel was
detected between points where x3=678 and x4=755. The third wheel
was detected between points where x5=766 and x6=842. The fourth
wheel was detected between points where x7=842 and x8=949. The
spacing between the second axle and third axle was greater than the
axle spacing between the third axle and the forth axle on this
vehicle. This difference in axle spacing was reflected in the
pattern of the detection of the axle group consisting of the third
and fourth axles.
[0274] This loop design provides good increases in the frequency of
the loop circuit when wheels of vehicles travel through the field
of the loop even when the length of the loop is made longer than a
group of wheels. This unique single loop design provides good wheel
detection for the population of vehicles from motorcycles to
tractor-trailers. This design can be wide enough to provide
detection of both the left and right wheels of a vehicle on a
single loop. This efficient design only requires one loop per lane
for wheel detection of the entire wheel population. Examples of the
different wheel sizes found in random traffic include, for example:
motorcycles, 12 to 23 inches in diameter; automobiles, 23 to 26
inches in diameter; pickup or SUV, 26 to 29 inches in diameter;
small trucks, 30 to 32 inches in diameter; and large trucks, 40 to
44 inches in diameter.
[0275] Both loop geometries, i.e., the gradient spacing and the
equal spacing designs, can be installed using one continuous wire
in two adjacent segments. This provides detection of the left and
right wheel paths in a roadway. This design can be used on wider
roadways. The use of two segments reduces the amount of wire in the
middle section of the loop. This design provides a wider detection
area without dramatically increasing the amount of wire being used.
The advantage of not increasing the amount of wire is that adding
additional wire does not decrease the loop sensitivity. This is
illustrated in FIG. 45 where a loop array has two adjacent loop
segments. Loop array 4502 has a gradient of different spacing
between the wire turnings. Loop array 4504 has wire turnings with
equal spacing.
[0276] Plots shown in FIGS. 45A-45I were produced using a loop that
is 10 feet wide by 28 inches using the same spacing 7 inches
wide.
Example No. 17
[0277] Plot 4510 shown in FIG. 45A illustrates the detection of a
car having two axles. The approximate wheel diameter on the car was
24 inches. The first wheel was detected between points where x1=290
and x2=435. The second wheel was detected between points where
x3=577 and x4=640.
Example No. 18
[0278] Plot 4520 shown in FIG. 45B illustrates the detection of a
pickup truck having two axles. The approximate wheel diameter on
the pickup truck was 29 inches. The first wheel was detected
between points where x1=591 and x2=638. The second wheel was
detected between points where x3=717 and x4=752.
Example No. 19
[0279] Plot 4530 shown in FIG. 45C illustrates the detection of a
pickup truck towing a trailer having two axles. The approximate
wheel diameter on the pickup truck was 29 inches. The first wheel
was detected between points where x1=774 and x2=878. The second
wheel was detected between points where x3=1052 and x4=1144. The
trailers wheels were detected between points where x5=1367 and
x6=1426 and between points where x7=1426 and x8=1480.
Example No. 20
[0280] Plot 4540 shown in FIG. 45D illustrates the detection of a
SUV having two axles. The approximate wheel diameter on the SUV was
29 inches. The first wheel was detected between points where x1=495
and x2=562. The second wheel was detected between points where
x3=641 and x4=696.
Example No. 21
[0281] Plot 4550 shown in FIG. 45E illustrates the detection of a
truck having two axles and towing a single axle device. The
approximate wheel diameter on the truck was 30 inches. The first
wheel was detected between points where x1=150 and x2=304. The
second wheel was detected between points where x3=556 and x4=692
and the amplitude for this detection was greater because of the
presence of the dual tire assembly. The third wheel was detected
between points where x5=968 and x6=1055.
Example No. 22
[0282] Plot 4560 shown in FIG. 45F illustrates the detection of a
truck having three axles. The approximate wheel diameter on the
truck was 40 inches. The first wheel was detected between points
where x1=462 and x2=533. The second wheel was detected between
points where x3=669 and x4=733. The third wheel was detected
between points x5=733 and x6=786.
Example No. 23
[0283] Plot 4570 shown in FIG. 45G illustrates the detection of a
truck having four axles. The approximate wheel diameter on the
truck was 40 inches. The first wheel was detected between points
where x1=347 and x2=448. The second wheel was detected between
points where x3=575 and x4=645. The third wheel was detected
between points where x5=645 and x6=713. The fourth wheel was
detected between points where x7=713 and x8=775.
Example No. 24
[0284] Plot 4580 shown in FIG. 45H illustrates the detection of a
truck having five axles. The approximate wheel diameter on the
truck was 40 inches. The first tire was detected between points
where x1=183 and x2=304. The second wheel was detected between
points where x3=544 and x4=647. The third wheel was detected from
points where x5=647 and x6=747. The fourth wheel was detected
between points where x7=1144 and x8=1207. The fifth wheel was
detected between points where x9=1207 and x10=1274.
Example No. 25
[0285] Plot 4590 shown in FIG. 45I illustrates the detection of a
truck having six axles. The approximate wheel diameter on the truck
was 40 inches. The first wheel was detected between points where
x1=70 and x2=1.60. The second wheel was detected between points
where x3=340 and x4=411. The third wheel was detected between
points where x5=411 and x6=482. The fourth wheel was detected
between points where x7=887 and x8=959. The fifth wheel was
detected between points where x9=959 and x10=1020. The sixth wheel
was detected between points where x11=1020 and x12=1082.
[0286] Another unique feature of this design is its ability to
increase the length of the loop without dramatically changing the
field height. This is very beneficial in supplying a longer sample
length time from the loop. The other benefit of having a longer
loop length is it provides wheel speed information. The travel path
length of the loop is longer than the diameter of the wheels it is
detecting. The additional field length provides improved wheel data
samples by providing a longer sample length. These longer samples
allow more information about each wheel to be processed.
[0287] The geometry of the ferromagnetic design can also be used to
calculate the speed of the vehicle. The speed can be measured using
the length of the sample time as the wheel assembly travels from
the leading edge of the loop to the trailing edge of the loop. The
sample time is used by the signal analyzer to calculate the speed
and provides an accuracy level of plus or minus about four
milliseconds. Also, the size and type of wheel assembly can be
determined using this loop geometry. The size of the wheel diameter
and/or a dual-wheel assembly is reflected in the increased
amplitude of the change in the frequency of the loop circuit. All
these factors contribute to the area of the curve represented in
the graphs for the detection of the wheel. The physical factors
about the wheel assembly are represented by the slope and amplitude
of the wheel detection. This also allows the processing unit to
validate the detection of a wheel and discriminate between an
object on a vehicle that is close to the ground but lacks the
amplitude and slope to be a valid wheel assembly. This information
is supplied on each wheel. In low speed applications or in
congestion, this can accurately measure changes in the vehicle
speed between the first axle and any of the following axles.
[0288] The width of the loop that is perpendicular to the direction
of travel can be adjusted to provide the proper width for detection
area. The length of the loop can be increased to increase the
length of the sample time. The chassis height of the vehicle can
also be detected providing the discrimination between cars, pickup,
small trucks, or large trucks on a single loop.
[0289] Using the ferromagnetic loop of the present invention, it is
now possible to detect wheel assemblies and measure vehicle speed
using only one single loop. The loop field can be made longer when
vehicle wheels travel at high speeds. This change in loop length
provides good axle detection even when the loop field length is
longer than the diameter of the wheels being detected. The loop
length can also be longer than a group of axles. The spacing width
of the coils within the loop can be varied to as small as two
inches to provide a lower field height. The spacing could also be
increased to 20 inches or more to detect very large vehicle wheels.
Thus, different coil spacing can be used on a single loop circuit.
The benefit of the geometry design is that the field density and
uniform field height can be adjusted by changing the spacing. The
loop circuit frequency increases when wheels travel through the
detection field and this provides easy identification of the
wheels.
[0290] There is another unique loop geometry design that has a
bi-symmetrical off-set of the left and right leading and trailing
edge of the loop. The left segment of the loop detects the wheels
from the left side of a vehicle and the right segment detects
wheels from the right side of a vehicle. The use of the offset
provides a longer travel distance over the loop and this provides a
longer sample time which is desirable particularly at high speeds.
In addition, this approach doubles the length of the sample time
but only slightly increases the amount of the loop wire by the
length of the offset. This loop design is illustrated in FIG. 46.
The loops shown in FIG. 46 have wires diagonal to the direction of
traffic. However, in other embodiments, the wire need not be
diagonal as shown. For example, in FIG. 46A, the gradient and equal
coil spacing is oriented perpendicular to the direction of
travel.
[0291] In FIG. 46B, the wire turnings of an offset loop are
illustrated.
[0292] In FIG. 46C, the wire turnings of the offset loop are
confined within a footprint with the shape of a parallelogram. This
shape provides additional detection in the center of a lane or
roadway.
[0293] FIG. 46D illustrates the wire turnings with the wire
perpendicular to the direction of travel.
[0294] FIG. 46E illustrates the use of additional wire turnings
(e.g., three or more turns) that can be used to increase the field
strength of the loop in regard to specific wire spacing in the
coils.
[0295] FIG. 46F illustrates the wire turnings of the offset loop
gradient characteristic.
[0296] FIG. 46G illustrates the offset gradient loop with diagonal
turnings at about 30 degrees to the leading and trailing edge of
the loop.
[0297] This offset loop design can also be used to calculate the
speed of the vehicles. This unique single loop design detects the
left wheel and right wheel of an axle assembly at different moments
in time. This design provides several methods of calculating the
speed on this offset wheel loop. These include loop total
activation time, activation time of the left and/or right segment,
sample time between left and right activation point, sample time
between left and right saturation point, and sample time between
left and right deactivation point. This is accomplished by having
the left segment of the loop and the right segment of the loop
being saturated by the left and right wheel at different moments in
time. This difference of time is related to the distance in the
offset between the left and right leading edge of the loop. Each
wheel provides an increase in the loop circuit frequency during
detection. These two increases mark the time it takes for the left
and right wheel to travel the distance equal to the offset of the
leading edge of the loop.
[0298] Also, the total time of the activation of the loop
represents the time the vehicle wheel travels the entire length of
the loop. These references can be used to calculate the speed of
the vehicle (i.e., distance divided by time) on each passing pair
of wheels. The axle spacing of the vehicle can also be calculated
providing vehicle classification information from a single wheel
loop.
[0299] Following are examples that illustrate how speed and axle
spacing of a vehicle can be determined using a single offset
wheel-loop shown in FIG. 47. The single offset wheel loop had a
left and right segment each of which was 28 inches long. The loop
had an offset length of 24 inches. The distance between the left
leading edge and the right leading edge is 52 inches (28+24). Note
that the offset distance between the left trailing edge and the
right leading edge can range preferably between zero and 46 inches.
The effective length of the loop equals 2835 milliseconds at one
mile per hour (mph). This is based on the fact that it takes 681.82
milliseconds to travel 12 inches or one foot at one mile/hour,
i.e., 1000 milliseconds/seconds.times.60seconds/minute.times.60
minutes/hour.times.hour/mile.times.5280 feet/mile, and 681.82
milliseconds/foot.times.52 inches.times.1 foot/12 inches=2954.55
milliseconds.
[0300] In each of Example Numbers 26 through 32 below, an
automobile having a known axle spacing of 8.3 feet was used. The
car was driven over the loop using a speed between 10 and 60 mph.
The speed of the vehicle was first determined. The axle spacing
were then calculated based on the determined speed of the vehicle.
The speed was calculated using the activation time between the left
and right wheel. The axle spacing was calculated using the sample
time between the activation of the first axle and the activation
point of the second axle. The spacing was calculated using the
vehicle speed measured on the first axle. It should be noted that
the speed calculation was available for each passing pair of
wheels. This speed information can also be used to determine if the
vehicle was accelerating or decelerating as it traveled over the
loop. It was also possible to use other or multiple speed points
and/or use the average of these points. When this offset distance
is used a valley or deactivation period appears on the graph (the
frequency vs. time plot) between the left and right wheel
detection. When a vehicle that has a group of axles with a spacing
that is less then the distance of the offset was detected, an axle
group pattern is produced on the graph.
Example No. 26
[0301] Plot 4710 shown in FIG. 47A illustrates the detection of the
car. The first left leading edge activation was at point where
x1=774 and the first right leading edge activation was at point
where x2=815. This represented a lapse of time of 225.5
milliseconds (i.e., (815-774) multiplied by 5.5). The 225.5
milliseconds sample time was divided into the effective length of
the loop value of 2954.55 milliseconds per one mph. This resulted
in 13.10 mph (2954.55/225.5) for the vehicle speed. This speed
factor was used with the sample time from the activation of the
first left leading edge of the first axle at point where x1=774 and
the activation of the left leading edge of the second axle at point
where x3=855. This represented a sample length of 445 milliseconds
((855-774).times.5.5). This resulted in an axle spacing of 8.54
feet.
Example No. 27
[0302] Plot 4720 shown in FIG. 47B illustrates a second detection
of the car. The first left leading edge activation was at point
where x1=546 and the first right leading edge activation was at
point where x2=594. This represented a lapse of time of 264
milliseconds. The 264 milliseconds sample time was divided into the
effective length of the loop value of 2835 milliseconds per one mph
to provide a result of 11.19 mph for the vehicle speed. This speed
factor was used with the sample time from the activation of the
first left leading edge of the first axle at point where x1=546 and
the activation of the left leading edge of the second axle at point
where x3=639. This represented a sample length of 511.5
milliseconds. This resulted in an axle spacing of 8.39 feet.
Example No. 28
[0303] Plot 4730 shown in FIG. 47C illustrates the third detection
of the car. The first left leading edge activation was at point
where x1=390 and the first right leading edge activation was at
point where x2=442. This represented a lapse of time of 286
milliseconds. The 286 milliseconds sample time was divided into the
effective length of the loop value of 2954.55 milliseconds per one
mph to provide a result of 10.33 mph for the vehicle speed. This
speed factor was used with the sample time from the activation of
the first left leading edge of the first axle at point where x2=442
and the activation of the left leading edge of the second axle at
point where x3=540. This represented a sample length of 539
milliseconds. This resulted in an axle spacing of 8.16 feet.
Example No. 29
[0304] Plot 4740 shown in FIG. 47D illustrates the fourth detection
of the car. The first left leading edge activation was at point
where x1=518 and the first right leading edge activation was at
point where x2=555. This represented a lapse of time of 203.5
milliseconds. The 203.5 milliseconds sample time was divided into
the effective length of the loop value of 2954.55 milliseconds per
one mph to provide a result of 14.51 mph for the vehicle speed.
This speed factor was used with the sample time from the activation
of the first left leading edge of the first axle at point where
x1=518 and the activation of the left leading edge of the second
axle at point where x3=589. This represented a sample length of 391
milliseconds. This resulted in an axle spacing of 8.31 feet.
Example No. 30
[0305] Plot 4750 shown in FIG. 47E illustrates the fifth detection
of the car. The first left leading edge activation was at point
where x1=409 and the first right leading edge activation was at
point where x2=429. This represented a lapse of time of 110
milliseconds. The 110 milliseconds sample time was divided into the
effective length of the loop value of 2954.55 milliseconds per one
mph to provide a result of 26.85 mph for the vehicle speed. This
speed factor was used with the sample time from the activation of
the first left leading edge of the first axle at point where x1=409
and the activation of the left leading edge of the second axle at
point where x3=447. This represents a sample length of 209
milliseconds. This resulted in an axle spacing of 8.23 feet.
Example No. 31
[0306] Plot 4760 shown in FIG. 47F illustrates the sixth detection
of the car. The first left leading edge activation was at point
where x1=275 and the first right leading edge activation was at
point where x2=286. This represented a lapse of time of 60.5
milliseconds. The 60.5 milliseconds sample time was divided into
the effective length of the loop value of 2954.55 milliseconds per
one mph to provide a result of 48.83 mph for the vehicle speed.
This speed factor was used with the sample time from the activation
of the first left leading edge of the first axle at point where
x1=275 and the activation of the left leading edge of the second
axle at point where x3=297. This represented a sample length of 121
milliseconds. This resulted in an axle spacing of 8.66 feet.
Example No. 32
[0307] Plot 4770 shown in FIG. 47G illustrates the seventh
detection of the car. The first left leading edge activation was at
point where x1=536 and the first right leading edge activation was
at point where x2=545. This represented a lapse of time of 49.5
milliseconds. The 49.5 milliseconds sample time was divided into
the effective length of the loop value of 2954.55 milliseconds per
one mph to provide a result of 59.68 mph for the vehicle speed.
This speed factor was used with the sample time from the activation
of the first left leading edge of the first axle at point where
x1=536 and the activation of the left leading edge of the second
axle at point where x3=554. This represented a sample length of 99
milliseconds. This resulted in an axle spacing of 8.66 feet.
[0308] The slope of the frequency vs. time plot can also be used to
calculate the speed of the wheel in slower speed conditions. The
slope of the wheel activation (rise over time) and/or wheel
deactivation (fall over time) can be calculated and compared to the
predetermined values of a loop calibration table or loop
calibration factor. The area under the slope of the wheel
activation (rise over time) and wheel deactivation (fall over time)
can also be calculated and compared to the predetermined values of
a loop calibration table or loop calibration factor. These three
methods are not as direct as using the left wheel to right wheel
saturation points or total activation time to provide calculations
for the speed of the vehicle to be measured with each pair of
wheels. This sensor is unique in shape and function by providing
accurate measurement of vehicle speed using only a single wheel
loop. This also provides the ability to supply vehicle
classification on a single loop.
[0309] The information from one offset loop can be processed to
provide axle counts, axle speeds, and axle spacing information. The
information is obtained from a single inductive loop and a single
loop detector. This loop design makes it possible to provide
vehicle classification on the basis of axle detection and axle
spacing using a single loop and single channel of detection in a
travel lane. The following examples illustrate the vehicle speed
and axle spacing being detected on a single offset wheel loop. The
speed of the vehicle was calculated and the axle spacing was
calculated based on the determined speed of the vehicle. This loop
had a left and right segment each 28 inches long and an offset
length of 24 inches. The effective length of the loop equals
2954.55 milliseconds at one mph. The speed was calculated using the
activation time between the left and right wheel. The axle spacing
was determined using the sample time between the activation of the
first axle and the activation point of the second axle. The spacing
is calculated using the vehicle speed measured on the first axle.
It should be noted that the speed calculation is available for each
passing pair of wheels. This speed information can also be used to
determine if a vehicle is accelerating or decelerating as it
travels over the loop. It is also possible to use other sample
points or multiple speed points and/or use the average of multiple
samples.
[0310] In the following Example Nos. 33-38, all the vehicles were
accelerating as they traveled over the offset loop.
Example No. 33
[0311] Plot 4810 shown in FIG. 48A illustrates the detection of a
car towing a one-axle trailer. The first left leading edge
activation was at point where x1=569 and the first right leading
edge activation was at point where x2=644. This represented a lapse
of time of 412.5 milliseconds. The 412.5 milliseconds sample time
was divided into the effective length of the loop value of 2954.55
milliseconds per one mph to provide a result of 7.16 mph for the
vehicle speed. This speed factor was used with the sample time from
the activation of the first left leading edge of the first axle at
point where x1=569 and the activation of the left leading edge of
the second axle at point where x3=728. This represented a sample
length of 874.5 milliseconds. This resulted in an axle spacing of
9.18 feet. The sample time to the trailer was 874.5 milliseconds,
which represented a spacing of 9.07 feet.
Example No. 34
[0312] Plot 4820 shown in FIG. 48B illustrates the detection of a
pickup truck. The first left leading edge activation was at point
where x1=276 and the first right leading edge activation was at
point where x2=340. This represented a lapse of time of 352
milliseconds. The 352 milliseconds sample time was divided into the
effective length of the loop value of 2954.55 milliseconds per one
mph to provide a result of 8.39 mph for the vehicle speed. This
speed factor was used with the sample time from the activation of
the first left leading edge of the first axle at point where x1=276
and the activation of the left leading edge of the second axle at
point where x3=437. This represented a sample length of 885.5
milliseconds. This resulted in an axle spacing of 10.89 feet. The
sample time for the second speed was 286 milliseconds, which
represented a speed of 10.33 mph.
Example No. 35
[0313] Plot 4830 shown in FIG. 48C illustrates the detection of a
pickup truck towing a two-axle trailer. The axle spacing on the
trailer produced an axle group pattern on plot 4830 since the axle
spacing was shorter than the length of 52 inches. The first left
leading edge activation was at point where x1=620 and the first
right leading edge activation was at point where x2=710. This
represented a lapse of time of 495 milliseconds. The 495
milliseconds sample time was divided into the effective length of
the loop value of 2954 milliseconds per one mph to provide a result
of 5.96 mph for the vehicle speed. This speed factor was used with
the sample time from the activation of the first left leading edge
of the first axle at point where x1=620 and the activation of the
left leading edge of the second axle at point where x3=827. This
represented a sample length of 1138.5 milliseconds. This resulted
in an axle spacing of 9.95 feet. The sample time for the second
axle speed was 402 milliseconds, which represented a speed of 7.34
mph. The sample time to the first trailer axle was 1419
milliseconds, which represented a spacing of 15.29 feet. The sample
time to the second trailer axle is 319 milliseconds, which
represented a spacing of 3.43 feet.
Example No. 36
[0314] Plot 4840 shown in FIG. 48C illustrates the detection of a
truck with 3 axles. The axle spacing between the second and third
axle produced an axle group pattern on plot 4840 since the axle
spacing was shorter than 52 inches. The first left leading edge
activation was at point where x1=326 and the first right leading
edge activation was at point where x2=388. This represented a lapse
of time of 341 milliseconds. The 341 milliseconds sample time was
divided into the effective length of the loop value of 2954.55
milliseconds per one mph to provide a result of 8.66 mph for the
vehicle speed. This speed factor was used with the sample time from
the activation of the first left leading edge of the first axle at
point where x1=326 and the activation of the left leading edge of
the second axle at point where x3=530. This represented a sample
length of 1122 milliseconds. This resulted in an axle spacing of
14.25 feet. The sample time for the second axle speed was 286
milliseconds, which represented a speed of 10.33 mph. The sample
time to the third axle was 275 milliseconds, which represented a
spacing of 4.16 feet.
Example No. 37
[0315] Plot 4850 shown in FIG. 48E illustrates the detection of a
truck with 4 axles. The axle spacing between the second, third, and
fourth axle produced an axle group pattern since each axle spacing
was shorter than 52 inches. The left leading edge activation of the
first axle wheel was at point where x1=107 and the right leading
edge activation of the first axle wheel was at point where x2=190.
This represented a lapse of time of 457 milliseconds. The 457
milliseconds sample time was divided into the effective length of
the loop value of 2954.55 milliseconds per one mph to provide a
result of 6.46 mph for the vehicle speed. This speed factor was
used with the sample time from the activation of the left leading
edge of the first axle at point where x1=107 and the activation of
the left leading edge of the second axle at point where x3=303.
This represented a sample length of 1078 milliseconds. This
resulted in an axle spacing of 10.22 feet. The left leading edge
activation point of the second axle was at point where x3=303 and
the first right leading edge activation of the second axle wheel
was at point where x4=364. This represented a sample length of
335.5 milliseconds. This represented a speed of 8.08 mph. The
saturation point of the left second axle wheel was at point where
x5=321. The saturation point of the left third axle wheel was at
x6=389. This represented a sample length of 374 milliseconds and a
spacing of 4.83 feet for the third axle. The saturation point of
the left third axle wheel was at point where x6=389. The saturation
point of the left fourth axle wheel is at point where x7=448. This
represented a sample length of 325 milliseconds and a spacing of
3.85 feet for the fourth axle.
Example No. 38
[0316] Plot 4860 shown in FIG. 48F illustrates the detection of a
truck with 5 axles. The axle spacing on this vehicle produced two
axle group patterns between the second and third axles, and between
the fourth and fifth axle since each of these axle spacing was less
than 52 inches. The left leading edge activation of the first wheel
was at point where x1=101 and the first right leading edge
activation of the first axle wheel was at point where x2=200. This
represented a lapse of time of 545 milliseconds. The 545
milliseconds sample time was divided into the effective length of
the loop value of 2954.55 milliseconds per one mph to provide a
result of 5.42 mph for the vehicle speed. This speed factor was
used with the sample time from the activation of the left leading
edge of the first axle at point where x1=101 and the activation of
the left leading edge of the second axle at point where x3=428.
This represented a sample milliseconds length of 1799 milliseconds.
This resulted in an axle spacing of 14.30 feet. The left leading
edge activation was at point of the second axle was at point where
x3=428 and the first right leading edge activation of the second
axle wheel was at point where x4=516. This represented a sample
length of 484 milliseconds. This represented a speed of 6.10 mph.
The saturation point of the left second axle wheel was at point
where x5=476. The saturation point of the left third axle wheel is
at point where x6=560. This represented a sample length of 462
milliseconds and a spacing of 4.13 feet for the third axle. The
saturation point of the left third axle wheel was point where
x6=560. The saturation point of the left fourth axle wheel was at
point where x7=643. This represented a sample length of 457
milliseconds and a speed of 6.46 mph. The left leading edge
activation was at point of the third axle was point where x8=516
and the first left leading edge activation of the fourth axle wheel
was at point where x9=757. This represented a sample length of 1326
milliseconds. This represented an axle spacing of 12.56 feet. The
left leading edge activation was at point of the fourth axle was at
point where x9=757 and the first right leading edge activation of
the fourth axle wheel was at point where x10=833. This represented
a sample length of 418 milliseconds. This represented a speed of
7.06 mph. The saturation of the fourth left axle wheel was at point
where x11=798, and the saturation of the left axle wheel on the
fifth axle was at point where x12=872. This represented a sample
length of 407 milliseconds and a spacing of 4.21 feet for the fifth
axle.
[0317] With respect to the wire spacing and the orientation of the
wire for the ferromagnetic loop, a number of factors should be
considered. For example, the orientation of the wire turnings with
respect to the path on which the wheel travels through the field
affects the loop frequency change. When the wire wrappings are
parallel to the direction of traffic, the field detects not only
the wheels but also the chassis of the vehicles. Using larger
spacing in wire turnings that are parallel to the direction of
travel affect the loop's ability so that it detects wheels
exclusively. However, when the large spacing is used, the chassis
of smaller vehicles such as motorcycles and cars with low ground
clearance can create eddy currents, which cause the frequency of
the loop circuit to lower and thereby reduces detection of wheels.
Accordingly, it is desirable to design the spacing of the loop
based on anticipated vehicles wheels to be detected. One novel
arrangement of the wire spacing is to route the wire at a 30 to 60
degrees angle to the direction of travel. This arrangement reduces
the eddy currents from the chassis. As a result, the arrangement
provides improved wheel detection and wheel speed information.
[0318] As discussed above, a ferromagnetic loop of the invention
can be used to determine, among other things, the presence, speed,
and number of axles of a vehicle. This can be accomplished as shown
in FIG. 49. Gradient loop 4900 is installed on path 4904. Gradient
loop 4900 is in communication with device 4902 via lead-in 4908.
Device 4902 can be a loop detector, a traffic counter, or a traffic
classifier. A vehicle (not shown) traveling on path 4904 in
direction 4906 is detected by loop 4900 when the vehicle moves over
loop 4900.
[0319] FIG. 49A shows that a ferromagnetic loop can be configured
in an offset orientation. For example, loop 4910 may be configured
so that it has a left segment 4912 and a right segment 4914.
[0320] The use of more than one ferromagnetic loop in a roadway can
be used to provide vehicle classification. FIGS. 49B and 49C
illustrate the use of two wheel loops 4952 and 4954 in loop array
4950 for vehicle classification. Inner spacing 4930 is preferably
from about five feet to about eight feet long and outer spacing
4940 should be from about nine feet to about 15 feet. Both loops
4952 and 4954 are in communication with device 4902.
[0321] The use of spacings 4930 and 4940 provides sensor activation
or deactivation on both wheel loops from the wheels located on the
same two-axle vehicle. The wheel detections on the two wheel loops
occur at the same time or within a few milliseconds. This provides
wheel, wheel assembly, speed, and axle spacing information from the
same vehicle during the wheel detection. This wheel information
provides critical vehicle information about the vehicle speed and
axle spacing that pairs the vehicle axles and greatly simplifies
the vehicle classification process by providing matches for the for
vehicle classification. The sensor arrangement provides the linking
or pairing of front and rear wheels of a vehicle for about 80 to
85% of the vehicles in random traffic. This percentage of vehicles
represent the axle spacing for cars, sport utility vehicles, vans,
and pickup trucks that have axle spacing that is between the inner
and outer spacing of the two wheel loops.
[0322] FIG. 50 illustrates the arrangement of a loop array having
multiple wheel loops 5010, 5020, and 5030 that have different
lengths. This unique sensor arrangement can provide individual
wheel information with additional axle group information on a
longer loop and individual wheel information on a shorter wheel
loop. For example, by combining a wheel loop 56 inches long and a
gradient wheel loop 31.5 inches long, the 56-inch loop would
provide single axle and axle group information. The second wheel
loop would provide axle information. This combination of different
sensor lengths would increase the amount of vehicle information
about the vehicle. This could have an inner spacing of 84 inches
and an outer spacing of 321.5 inches. This wheel information
provides critical vehicle information about the vehicle speed, axle
spacing, and axle groups. Again, the spacing of these two wheel
sensors provides pairs of sensor activations occurring at the same
time or within a few milliseconds of each other. This arrangement
greatly simplifies the vehicle classification process by providing
matches of the vehicle axles and axle groups for the vehicle
classification. This sensor arrangement provides linking for about
85 to 90% of the vehicles in random traffic.
[0323] The addition of single rectangular or dipole loop located
between the two wheel loops could be used in heavy congested
traffic conditions to supply additional vehicle processing
information. The rectangular or dipole loop would provide
additional vehicle presents detection for axle spacing that are
greater than 19 feet long. FIG. 51 illustrates one embodiment of
this sensor arrangement that provides additional vehicle processing
information.
Installation
[0324] The ferromagnetic loops and its various configurations,
variations, arrangements, and arrays of loops of the present
invention can be installed as a surface mount loop for temporary
installation. In addition, the loops can be installed for permanent
applications using a pavement saw, drill, wire, and loop
sealant.
Installation Procedure for a Ferromagnetic Loop
[0325] The loop can be installed on a pavement as follows. The
pavement is marked using paint to outline the locations or a web of
grooves to be cut using a pavement saw. A slot is made by the saw
that is between about 0.75 inches wide by about 1.5 inch deep. The
loop is formed using a single conductor of preferably stranded wire
AWG number 14 with high density polyethylene insulation with a
jacket diameter of 130 to 140 mils. However, single or stranded
conductor wire gauge of 12, 14, 16, or 18 could be used for this
installation. It is recommended that the loop coils of wire are
kept parallel to the roadway surface (i.e., the coils of wire are
laid side-by-side). The wire is installed in the cut slot (see,
e.g., FIGS. 41, 43, and 44). The wire and slot is then filled with
a bonding agent. The bonding agent can be, for example, a loop
sealant. The lead-in wire is twisted continuously from the loop to
the signal processor.
[0326] Molded Ferromagnetic Loop and Installation Procedure
[0327] The unique design of the ferromagnetic loop can be made in a
molded loop in the same variety of geometric shapes, sizes, and
coil spacing as those formed using a pavement saw and wire method.
Molded loop 5300 shown in FIG. 53 has a unique shape 5302 that
provides a positive anchoring of the loop in the pavement. FIG. 53
illustrates several examples of the anchors 5304, 5306, 5308, 5310,
and 5312 that can be incorporated in the molded ferromagnetic loop.
Loop 5300 is secured by at least one fastener 5320 to maintain the
multiple contiguous polygons of loop 5300. The advantages for using
the molded loop included:
[0328] easy control of the loop depth during installation;
[0329] consistent wire turnings in the coils; and
[0330] reduction of the loop installation time.
[0331] The loop can be installed using a molded loop that can be
placed in a saw cut or a web of grooves created within a pavement.
For example, an outline of the loop is painted or marked on the
pavement. A pavement saw is used to cut slots about 0.75 inches
wide by about 1.5 inches deep. The molded loop is then placed in
the slots and a loop sealant or another bonding agent is used to
secure the molded loop in the saw cut. FIGS. 52 and 53 illustrate
various cross sectional views of the molded loop. An alternative
method involves the step of filling the web of grooves with the
loop sealant before placing the molded loop in the saw cut. The
molded loop is pressed down until the top of the loop is even with
the road surface. The molded loop has a twisted lead-in cable
continuously from the loop to the signal processor. The advantages
of using the molded loop is the wire turnings are horizontal and
parallel with the road surface. The depth of the loop installation
is easy to control by installing the top of the molded loop flush
to the surface of the road.
[0332] Installing Temporary Ferromagnetic Loop
[0333] Temporary loops can be made using a combination of wire and
seal tape having a woven Polypropylene mesh. The adhesive of the
road tape holds the loop in place in the road way. FIG. 54
illustrates a cross section of the construction of a temporary
wheel loop.
[0334] FIG. 55 illustrates temporary loop 5500 that is 10 feet wide
by 28 inches long having diagonal coils 5502.
Example No. 39
[0335] Plot 5510 shown in FIG. 55A illustrates the detection a
vehicle using loop 5500. The front wheels activation was between
points where x1=231 and x2=272. The rear set of wheels activation
was between points where x3=348 and x4=390.
Example No. 40
[0336] Plot 5520 shown in FIG. 55B illustrates the detection of a
pickup truck as it moves above temporary loop 5500. The front
wheels activation was between points where x1=2022 and x2=2074. The
rear set of wheels activation was between points where x3=2167 and
x4=2217.
Example No. 41
[0337] Plot 5530 shown in FIG. 55C illustrates the detection of a
truck with four axles moving above temporary loop 5500. The front
wheels activation was between points where x1=2204 and x2=2299. The
second set of wheels activation was between points where x3=2479
and x4=2547. The third set of wheels activation was between points
where x5=2563 and x6=2626. The fourth set of wheels activation was
between points where x7=2644 and x8=2705.
[0338] FIG. 56 illustrates temporary loop 5600 that is 10 feet wide
by 28 inches long having coils 5602 perpendicular to the travel
direction.
Example No. 42
[0339] Plot 5610 shown in FIG. 56A illustrates the detection of a
car moving above temporary loop 5600. The front wheels activation
was between points where x1=855 and x2=901. The rear set of wheels
activation was between points where x3=1005 and x4=1044.
Example No. 43
[0340] Plot 5620 shown in FIG. 56B illustrates the detection of a
pickup truck moving above temporary loop 5600. The front wheels
activation was between points where x1=181 and x2=242. The rear set
of wheels activation was between points where x3=372 and
x4=242.
Example No. 44
[0341] Plot 5630 shown in FIG. 56C illustrates the detection of a
truck with five axles moving above temporary loop 5600. The front
wheels activation was between points where x1=1240 and x2=1330. The
second set of wheels activation was between points where x3=1588
and x4=1651. The third set of wheels activation was between points
where x5=1670 and x6=1726. The fourth set of wheels activation was
between points where x7=2096 and x8=2138. The fifth set of wheels
activation was between points where x9=2144 and x10=2189.
[0342] FIG. 57 illustrates temporary offset loop 5700 that can be
installed on a roadway so that its coils 5704 can be perpendicular
or parallel to the direction of travel. Lead-in 5902 is connected
to a loop detector.
Example No. 45
[0343] Plot 5710 shown in FIG. 57A illustrates the detection of a
truck with two axles being detected on temporary offset loop 5700,
which is having coils 5704 perpendicular to the flow of travel in
direction 5706.
Example No. 46
[0344] Plot 5720 shown in FIG. 57B illustrates the detection of a
truck with two axles being detected on an offset loop having coils
parallel to the direction of travel.
[0345] Together, plots 5710 and 5720 indicate that offset loop 5700
can be used to detect vehicle wheels regardless of whether coils
5704 are parallel or perpendicular (or diagonal) to the direction
of travel.
[0346] The ferromagnetic loop of the present invention has many
characteristics including the following.
[0347] The loop geometry associated with the present invention is
unique. Preferred embodiments of the invention use wire turnings in
a serpentine fashion to provide a low density magnetic field for
the ferromagnetic loop. Preferably, the ferromagnetic loop provides
a wire coil with multiple turns to remain parallel (side-by-side)
and preferably one inch or less below the road surface.
[0348] The loop width can be larger than the diameter of the wheels
being detected to provide a longer sample time of each wheel
assembly.
[0349] The ferromagnetic loop design can detect and provide
distinctions for single wheel assemblies on small vehicle wheels,
automobiles, trucks and dual wheel assemblies on vehicles.
[0350] The loop design can be installed on a temporary basis using
flexible adhesive sheets. Alternatively, the loop can be formed to
contain the continuous wire. For example, the continuous wire can
be encapsulated or encased in a molding process to give form to the
loop circuit.
[0351] The loop circuit encapsulated or encased in a molding
process can be further secured by an anchoring system. The
anchoring system may consist one or more of plastic, rubber,
synthetic, and other resinous product for permanent
installations.
[0352] A molded loop designed specifically for temporary
installations can be installed as a surface mount loop. This loop
is designed to be reusable and more durable than the temporary
loops made of a combination of wire and seal tape having a woven
polypropylene mesh.
[0353] The permanent installations can use a shallow saw cut 0.5 to
0.75 inches wide and one inch deep to maintain close proximity of
the ferromagnetic circuit to the road surface.
[0354] The permanent installations can be installed in a saw cut
using a loop circuit that has been encapsulated or encased using a
molding process using one or more of plastic, rubber, synthetic,
and other resinous products.
[0355] The shape of the molded ferromagnetic loop design can be
adapted to be secured by a mechanical anchor in the saw cut.
[0356] The loop design has the ability to discriminate between a
single wheel assembly and a dual wheel assembly.
[0357] The unique serpentine method of wire turns can utilize
different length sizes of spacing to create a low dense gradient
field for different wheel diameters.
[0358] Temporary loops can be made from a combination of wire and
seal tape having a woven Polypropylene material with adhesive.
These temporary loops can be installed for short term or temporary
installations.
[0359] Vehicle classification by detecting axle counts, vehicle
spacing, and axle spacing can be done using a single loop.
[0360] Vehicle classification using two loops in series can have
spacing from 3 feet to 15 feet between loops.
[0361] Overview of the Present CIP Application
[0362] The foregoing disclosure of preferred embodiments of the
present invention has been presented for purposes of illustration
and description. Other embodiments and additional aspects on the
invention have been contemplated by the inventors. In particular,
aspects of the ferromagnetic loop sensor system described above can
be integrated with additional features in several additional
embodiments. In addition, vehicle sensors other than ferromagnetic
loops can be used in conjunction with the intelligent vehicle
identification system (IVIS), vehicle image capture unit (VICU),
multilane vehicle information capture system (MVIC), and vehicle
tracking system (VTS) of the present invention.
[0363] In one aspect, a vehicle sensor, e.g., a ferromagnetic loop
sensor, is incorporated in a VICU. In one aspect, the VICU may act
as a violation enforcement system (VES) for enforcing toll
violations. The VICU system includes a trigger unit, a capture
unit, and a lighting unit. The trigger unit is coupled to an IVIS,
which detects the presence of a vehicle and sends a trigger signal
to the capture unit. The capture unit takes vehicle images of the
vehicle that is lit by the lighting unit that provides a lighting
source incident on the vehicle. The system further includes a
processing unit that processes the vehicle images and controls the
exposure employed by the capture unit. The processing unit contains
an application program running in the processing unit, and
containing modules for vehicle image processing and exposure.
[0364] In another aspect, vehicle sensors, e.g., ferromagnetic loop
sensors, are incorporated in a system that contains an MVIC unit
for collecting information from MVIC subsystems. The tolling system
can also include an IVIS system. Preferably, the IVIS system
contains the ferromagnetic loop sensors, but other sensors may be
used. The IVIS system sends to the MVIC unit vehicle information.
Preferably, the information is sent at a rate of many times per
second. Also included are a vehicle tracking system (VTS) that
collects information about the vehicle position using vision
tracking sensors, and an RF system designed for reading a
transponder on a passing vehicle, as well as a vehicle image
capture system (VICU) for capturing images of the passing vehicle
when a camera in the VICU receives a trigger from the MVIC
unit.
[0365] In a further aspect, lane straddling sensors are
incorporated in a dual RF read zone system for conducting
transactions with high speed vehicles traveling on a road.
Preferably, the lane straddling sensors are diamond-shaped loop
sensors (also termed "lane straddling sensors"). The system
includes one or more gantries that contain RF read sources that
each extend over at least one lane of the highway. The system
creates multiple RF read zones for passing vehicles, so that
vehicle transactions can be completed with a high degree of
accuracy.
[0366] In another aspect of the invention, a system for IVIS
vehicle sensor synchronization includes a master program that
coordinates sampling periods of vehicle sensors so that adjacent
sensors do not have sampling periods at the same time.
Toll Violation Enforcement System
[0367] FIGS. 58 and 65 depict a block diagram and a schematic,
respectively, of a VICU 5800, acting as a toll violation
enforcement system (VES). VICU 5800 includes trigger unit 5802.
VICU 5800 is only one example of a VICU, designed for capturing
vehicle images to help enforce tolling operations. However VICU
5800 can be used for any application in which capturing of a
vehicle image is useful, such as law enforcement, or data
collection. Trigger unit 5802 is configured to detect the presence
of a vehicle in a toll environment or other traffic environment
when vehicle image capture is important. Unit 5802 can be in any
combination of one or more vehicle detection ferromagnetic loop
sensors, pressure sensors, radar sensors, and laser sensors.
Preferably, ferromagnetic loops are used in trigger unit 5802, for
example as shown in FIG. 65 for IVIS sensors 6503. Trigger unit
5802 can also be configured to include one or more vehicle
detectors that are based on digital video from one or more camera.
Trigger unit 5802 can be activated to send a triggering signal when
a vehicle triggers the triggering unit. In a preferred embodiment,
trigger unit 5802 comprises an IVIS system that includes a
processor (not shown) for sending a triggering signal to capture
unit 5804.
[0368] VICU 5800 also includes a capture unit 5804, which can
include a frame grabber and one or more cameras. The cameras can be
digital video cameras or analogue video cameras plus a frame
grabber. A preferred embodiment of the invention uses at least one
digital video camera. Capture unit 5804 can be mounted either
roadside or on a gantry above a traveling lane. Capture unit 5804
is configured to receive a trigger signal (or trigger) from trigger
unit 5802. Upon receiving the trigger signal, capture unit 5804 can
take one or more images of a passing vehicle that is detected by
trigger unit 5802.
[0369] VICU 5800 preferably includes lighting unit 5806. Lighting
unit 5806 can comprise a visible wavelength or infrared strobe
light, or flood light. In a preferred embodiment of the invention,
lighting unit 5806 employs a white strobe light. Preferably, a
diffuser is arranged in front of lighting unit 5806 to make a
lighting field created by the unit more uniform. When lighting unit
5806 is operational, it creates a lighting field that can
illuminate a passing vehicle. In one embodiment, lighting unit 5806
is also configured to receive the triggering signal from trigger
unit 5802 that can, for example, activate a strobe in lighting unit
5806.
[0370] VICU 5800 also includes processing unit 5808, which can be a
standard or embedded computer system that is located locally or at
a remote distance from capture unit 5804. Processing unit 5808
contains a processing program 5810 running therein. Preferably,
processing program 5810 is used for processing vehicle images sent
by capture unit 5804. Further, processing unit 5810 can be
configured to control exposure in capture unit 5804. In preferred
embodiments of the invention, unit 5808 comprises a standard
desktop computer, an industrial computer, or single-board
computer.
[0371] Application program 5810 is configured to run processing
unit 5808. Further, application program 5810 contains several
modules that can be used to process images received from capture
unit 5804, as described further below with reference to FIG.
59.
[0372] VICU 5800 further includes storage media 5812, which can be
local or remote memory, and in hard disk, flash disk, CD, or DVD
form. Storage media 5812 is used to store information such as
vehicle images received in digital form from processing unit 5808.
In general, the images received for storage can be digital data
representing as-received pictures of a passing vehicle taken by
capture unit 5804, or they can be digital data that has been
manipulated in some manner after being received from capture unit
5804 by processing unit 5808. For example, processing unit 5808 may
receive a "raw" vehicle image from capture unit 5808 and create a
brightened or darkened image, an extracted image, and the like (see
discussion below). All of these images can be stored as digital
data in storage media 5812. In the case where storage media 5812 is
located remotely, communication from processing unit 5808 to
storage media 5812 can be through a wireless, cable, or satellite
network. In preferred embodiments of the invention, a local hard
disk, local memory, or local flash disk are used for storage
media.
[0373] FIG. 59 discloses details of one exemplary embodiment of the
present invention in which application program 5810 contains plate
location module 5902, exposure control module 5904, resolution
resetting module 5906, image enhancement module 5908, and image
compression module 5910.
[0374] Plate location module 5902 is configured to find and extract
a license plate area in a vehicle image (also referred to as "whole
vehicle image") received from capture unit 5804. Typically, there
is a conflict between the needs to increase resolution for taking
accurate images of vehicles, and the limitations in storage
capacity and transmission rate of vehicle images. For example,
camera resolution and original image size are increasing to the
extent that image transmission and storage have become significant
problems. From the point view of both transmission and storage, low
image resolution (and therefore less data generated per image) is
preferred. From the point of view of optical character recognition
(OCR) and other processing purposes, higher image resolution image
is preferred, so that accurate information regarding a vehicle in
question is retained.
[0375] To solve this conflict, the present invention employs plate
location module 5902. As depicted in FIG. 60, plate location module
5902 is configured to find and extract a license plate area within
a whole vehicle image 6002, to create extracted plate area image
6004. Plate location module 5902 then maintains the extracted plate
area image 6004 at an original image resolution as received from
capture unit 5804.
[0376] Capture unit 5804 transmits whole vehicle image 6002 to
plate location module 5902, which processes the image to find and
extract a plate area image. Module 5902 can then output plate area
image 6004 at the original resolution as received in vehicle image
6002. However, the amount of data in plate area image 6004 is only
a fraction of the amount of data contained in original whole
vehicle image 6002, due to the relatively small size of a license
plate compared to a whole vehicle. For example, a typical whole
vehicle image 6002 can comprise about 1.4 megapixels (one megapixel
equals one million pixels), equivalent to 4.2 Mbytes of data, where
each pixel of a color image uses 3 bytes of data to represent a
red-blue-green image. On the other hand, plate area image 6004
having the same resolution as vehicle image 6002 comprises only
about forty thousand pixels, or about 120 Kbytes of data. In order
to minimize storage space associated with collecting a high
resolution plate image, such as image 6004, original image 6002 can
be discarded after being transmitted to and operated on by plate
location module 5902.
[0377] FIG. 61 includes whole vehicle image 6102 that depicts a
back portion of a passing vehicle including a plate area 6104. As
mentioned above, image 6102 is recorded at a first resolution,
where, for example, the total number of image pixels can be in the
range of one to one hundred megapixels or greater. In one
embodiment, the first resolution, in which vehicle image 6102 is
captured, is a relatively lower image resolution. Also displayed in
FIG. 61 is extracted plate image 6106, which in large part contains
an image of license plate, 6108. Preferably, plate image 6106 is
extracted from a full vehicle image (not shown) that is taken at a
second image resolution that is relatively higher than the first
resolution used for capturing whole vehicle image 6102. Characters
in image 6106 clearly read "4A1365D". Below image 6106 are
extracted character image 6110 that display images of each
character in the license plate "number." Preferably, an optical
character recognition (OCR) program or similar tool can be used to
determine a character corresponding to each extracted character
region and to display a corresponding determined character sequence
6112, which reads "4A1365D." Below each character of sequence 6112,
are confidence values 6114 reflecting the degree of probability
that a character has been determined accurately. In the example
shown in FIG. 61, the confidence values range from 0.89 to 1.00,
which indicates a high probability of reading the numbers
accurately.
[0378] Capture unit 5804 is preferably configured to rapidly change
between a plurality of different image resolution modes for taking
pictures. Accordingly, capture unit 5804 can take pictures in rapid
succession of a passing vehicle at a higher image resolution and a
lower image resolution. For example, after capturing a high
resolution whole vehicle image 6002, resolution resetting module
5906 can receive a signal so that capture unit 5804 can be reset to
take a second whole vehicle image 6006 at a lower resolution. For
example, image 6006 could comprise about 353 kilopxels, or about
one quarter of that of image 6002. This lower resolution image can
be used for image enhancement as described in more detail
below.
[0379] Also displayed in FIG. 61 is an image portion 6116 of lower
resolution vehicle image 6102 that includes low resolution license
plate area 6118. The legibility of downsized plate area 6118 is
comparatively poorer than a similar sized original resolution
extracted plate image 6108. However, portions of the lower
resolution image outside of area 6118 are sufficiently clear that
license plate position on the vehicle, taillight shape, and logo of
the vehicle manufacturer are discernable. Thus, lower resolution
image 6116 may not be appropriate for accurate automatic license
plate number determination, but is adequate for recording general
vehicle features.
[0380] Images 6004 and 6006 can then be transmitted to storage
media 5812 (see FIG. 59) for storage. In the example above, plate
image 6004 and lower resolution vehicle image 6006 together
comprise only about 393 thousand pixels. Preferably, the resolution
of whole vehicle image 6006 is sufficient for any needed purposes
of identification additional to the license plate identification
provided by image 6004. Thus, far less memory space is needed to
store images 6004 and 6006 as compared to 6002, but the reliability
of critical identifying information, such as a license plate
number, and other specific vehicle features, is maintained.
[0381] As further depicted in FIG. 59, exposure control module 5904
is configured to communicate with capture unit 5804 to control
exposure settings employed by capture unit 5804. In existing toll
violation enforcement systems, exposure setting of a capture unit
is based on intensity information from a whole vehicle image, so
that there is no guarantee that consistent intensity in the crucial
license plate area will be obtained.
[0382] In an embodiment of the present invention illustrated in
FIG. 62, plate location module 5902 receives a vehicle image from
capture unit 5804 and locates the plate area from the vehicle
image. It then forwards information from the plate area, preferably
including, e.g., image 6004, to exposure control module 5904.
Exposure control module 5904 then forwards exposure control
information 6202 to capture unit 5804 to control a camera exposure
setting. Exposure control information 6202 is preferably based on
intensity information associated solely from plate area image 6004.
Such exposure control process improves the consistency of image
intensity of vehicle plate areas that are captured by capture unit
5804. This acts to further increase the reliability of license
plate information received and stored by system 5800.
[0383] Referring back to FIG. 59, image enhancement module 5908 is
configured to receive whole vehicle images transmitted from capture
unit 5804. Image enhancement module 5908 can be used to improve
image features of a received whole vehicle image, for example.
[0384] In current systems that are used to take vehicle images for
law enforcement purposes, a typical reflectorized license plate
frequently appears much brighter than other parts of a vehicle.
This is especially true when a lighting unit is used to illuminate
a passing vehicle. Moreover, under certain circumstances, the
license plate may actually appear darker than the rest of the
vehicle. In general, the license plate area of an image differs in
brightness compared with the rest of the vehicle. This creates an
undesirable tradeoff: if the plate area has a normal intensity, the
vehicle body is too dark (or light) to see vehicle details; and if
the vehicle body is bright enough for resolution of vehicle
details, the plate area appears overexposed (or underexposed).
[0385] In an embodiment of the present invention, the above
conflict is addressed by initially controlling the exposure setting
of capture unit 5804 to capture a vehicle image so that the plate
area has normal brightness or intensity. As illustrated in FIG. 63,
capture unit 5804 transmits whole vehicle image 6302 to image
enhancement module 5908. Image 6302 contains plate area 6304 of
normal intensity, as well as whole vehicle area 6306 having a
different appearance, for example, a darker appearance. Image
enhancement module 5908 then processes image 6302 to brighten
pixels in area 6306 outside plate area 6304, such that brightened
vehicle image 6308 is produced, Where both plate and vehicle body
areas have reasonable brightness.
[0386] Image compression module 5910 (see FIG. 59) is configured to
perform compression on images received from capture unit 5804.
After compression, compressed images can be transmitted from image
compression module 5910 to storage media 5812 for storage. Image
compression is performed such that compression can be either lossy
(like JPEG etc.) or lossless (like Huffrnan, Arithmetic, LZW, GIF,
lossless JPEG, or other known compression techniques). Compression
may be performed, for example on images received from capture unit
5804 via modules 5902 or 5908. In an embodiment of the present
invention depicted in FIG. 64, image compression module 5910
receives input from plate location module 5902 and image
enhancement module 5908. For example, plate location module 5902
transmits plate image 6401 derived from higher resolution vehicle
image 6402 to compression module 5910. Image enhancement module
5908 receives a second, lower resolution vehicle image 6402 and
transmits a brightened lower resolution full vehicle image 6406 to
module 5910. Module 5910 then compresses images 6404 and 6406 to a
predetermined format for output to storage media 5812.
[0387] FIG. 65 illustrates more details of features of VES 6500
according to an embodiment of the present invention. When a vehicle
passes over trigger unit 6502 comprising ferromagnetic induction
loop regions 6503, a change in inductance measured in the loops
causes a signal to be sent to camera 6504. Note that in other
embodiments, vehicle detectors other than ferromagnetic loops may
be used. Camera 6504 is configured to take images of a passing
vehicle that may be illuminated by strobe light 6506. In a
preferred embodiment, strobe 6506 is triggered to activate when a
vehicle is detected by trigger unit 6502. Preferably, a camera
setting for camera 6504 is performed during an installation
procedure for the camera. The setting of the camera's iris can be
done in such a way that under normal exposure setting, a license
plate image is clearly visible only when a lighting unit, such as
strobe 6506, is working. Such a setting minimizes the influence of
variations in ambient light on images of vehicle license
plates.
[0388] A lighting unit in existing conventional toll enforcement
systems works as compensation lighting and is turned on only when
the ambient light is low due to a time of day or poor weather
conditions. However, the ambient light still varies widely over the
range of conditions where the ambient light is bright enough for no
use of a lighting unit. Sunlight might shine in the field of view
of a camera in an unpredictable manner due to floating clouds.
Additionally, sunlight incident directly on a license plate, such
as during sunrise, sunset or other coincident situations, can make
a plate appear extremely bright and completely overexposed. These
factors render it difficult to control exposure to capture images
with consistent intensity.
[0389] By employing a major light source adjusted so that a license
plate is not over-exposed when the source is on, the effects of
ambient light can be greatly reduced. Thus, in a preferred
embodiment, to minimize the influence of ambient light, a lighting
unit of the present invention uses a major lighting source that is
preferably operating substantially all the time, with camera
settings adjusted so that a plate image is clearly visible only
when the lighting source is operational. For example, a strobe unit
6506 is continuously operational so that it is triggered to expose
a vehicle every time a passing vehicle is detected.
[0390] To further reduce the effect of direct sunshine on the
ability to obtain good images, in an embodiment of the present
invention, multiple different predetermined capture positions of
cameras are employed so that two or more images are taken for each
passing vehicle. Since the intensity of direct sunshine reflected
from a plate and detected in a capture unit depends highly on the
sunshine angle and view angle of the capture unit, changing a
capture position, which also changes the view angle of the capture
unit, likely results in at least one image position not receiving
directly reflected sunlight. In addition, since often at lease one
capture position might be located in the shadow of a surrounding
object, such as a toll plaza canopy, use of multiple capture
positions greatly increases the chance of capturing at least one
good image when direct sunshine is present. Thus, as a vehicle
passes by, images are collected at different points in time by a
capture unit camera, such that each different image reflects a
different capture position. Preferably, the strobe unit and capture
unit are positioned to capture a license plate image of consistent
intensity every time a passing vehicle is photographed at least one
predetermined capture position.
[0391] VES system 6500 may include a frame grabber (not shown) that
is coupled to a lane controller interface 6508. Lane controller
interface 6508 is also coupled to IVIS board 6512 that collects
signals from IVIS 6503. Lane controller interface is additionally
coupled to camera 6504 and strobe 6506.
[0392] FIG. 66 illustrates exemplary steps for a method for toll
violation enforcement according to an exemplary embodiment of the
present invention. In the following discussion, reference to FIGS.
58-63 is made to add clarity. Note that in some embodiments of the
invention, some of the steps are optional.
[0393] In step 6602, a trigger unit detects the presence of a
passing vehicle. As discussed above, trigger unit 5802 preferably
includes an induction loop sensor embedded in the roadway that is
configured to detect the presence of a vehicle overhead by sensing
changes in inductance, but may include any other convenient means
for detecting passing vehicles.
[0394] In step 6604, trigger unit 5802 send a trigger signal to
capture unit 5804.
[0395] In step 6606, the trigger signal is also sent to lighting
unit 5806, if unit 5806 includes a strobe light. The trigger signal
can cause the strobe light to illuminate the passing vehicle.
[0396] In step 6608, capture unit 5804 takes a first image of the
passing vehicle. In one embodiment of the present invention, the
first image is taken at a predetermined image resolution. For
example, camera 6504 can be configured to capture a first image of
a passing vehicle at high resolution. Accordingly, after a vehicle
is detected by trigger unit 6503, camera 6504 is automatically set
for higher resolution vehicle image capture.
[0397] In step 6608, the exposure setting may also be set at a
predetermined value based on, for example the type of image to be
collected. If the first image is to be used to produce an extracted
plate image, the capture exposure setting can be adjusted to
produce optimum lighting conditions for obtaining a legible plate
image.
[0398] In step 6610, the first vehicle image is transmitted to
processing unit 5808 to be processed by program 5810 residing
therein.
[0399] In step 6612, the image resolution of capture unit is
changed from that employed in step 6608. Following the example of
step 6608, if the image resolution for image capture at that step
was a higher resolution, then in step 6612, the image resolution
for image capture by capture unit 5804 is reduced to a lower
resolution. However, in another embodiment, the image resolution
for capture unit 5804 can be lower in step 6608 and relatively
higher in step 6612.
[0400] In step 6614, a second vehicle image, for example, a lower
resolution vehicle image, is taken. System 6500 is configured so
that the first and second vehicle images can be taken with a
minimum time lapse between successive images. For example, the
second vehicle image can be taken at an interval ranging between
about two and three hundred] milliseconds after the first vehicle
image. Thus, the first and second vehicle images can represent very
similar views of the passing vehicle, for example, in terms of
vehicle size and angle of view.
[0401] In one embodiment of the present invention, the second
vehicle image taken in step 6614 is captured at an exposures
setting different from that of the first vehicle image taken in
step 6608. For example, if the second vehicle image is to be used
to produce and store a whole vehicle image, the exposure setting
may be adjusted to be greater than that used in step 6608, if the
image in step 6608 is used to produce an extracted plate image.
This is because the extracted plate region typically is more highly
reflective and may appear much brighter than the rest of the
vehicle, and accordingly require a lower exposure setting than that
to be used to capture whole vehicle information.
[0402] In one embodiment, exposure control module 5904 and
resolution resetting module 5906 are set to automatically toggle
between different exposure and different resolution settings. For
example, in an initial state, exposure control module 5904 is set
at a lower exposure time and a higher resolution in order to
capture a clear license plate image. After capture unit 5804 takes
an initial picture of a passing vehicle a signal is received by
units 5904 and 5906, upon which the image capture exposure time for
capture unit 5804 is reset to a longer time and the image
resolution for capture unit 5804 is set at a lower resolution.
Accordingly, a second vehicle image appropriate for whole vehicle
image capture can be taken at the longer exposure time and lower
resolution that are more appropriate for capturing and storing a
whole vehicle image. For example, the vehicle as a whole may be
typically less reflective than a plate area, requiring a longer
exposure time, but less resolution is generally required to resolve
the general vehicle features besides those license plate features
captured in the higher resolution image. In this manner, in this
embodiment, the "capture state" of capture unit 5804, where the
"capture state" includes the image resolution setting and the
exposure setting, can be automatically and rapidly toggled between
settings appropriate for plate image capture and whole vehicle
image capture.
[0403] In step 6616, the second image is transmitted to unit 5810
for processing.
[0404] In step 6618, the resolution for image capture of capture
unit 5804 is reset to the predetermined resolution, for example, a
higher resolution, used in step 6608. Accordingly, a subsequent
passing vehicle will have a first image taken at the same
predetermined resolution as the first vehicle.
[0405] In step 6620, an extracted plate image is taken from one of
the first or second vehicle images, whichever is higher. Following
the example where the image resolution of a first vehicle image
taken in step 6608 is a higher resolution, then the plate image is
extracted from the first vehicle image. As discussed above, this
allows for optimal identification of plate image information by
preserving a high resolution image of the plate.
[0406] In step 6622, intensity information taken from the plate
region of the high resolution image (in the example of steps 6608
and 6620 of FIG. 66, this is the first image) is forwarded to an
exposure control module.
[0407] In step 6624, the intensity information from the plate
region of the high resolution image is compared to stored intensity
data.
[0408] In step 6626, the settings on a capture unit, for example,
unit 5804, are adjusted based on the comparison of stored intensity
data and that received from the most recent high resolution plate
image. For example, lighting conditions may have varied between the
time when the stored intensity data was collected and the time when
the intensity data from the plate region of the most recent vehicle
was taken. In this manner, the exposure settings for capture of the
next vehicle can be adjusted, both for the high resolution image to
be used to capture an image of a highly reflective plate, and a
lower resolution image, to be used to collect an image from a less
reflective whole vehicle.
[0409] In step 6628, a brightened image of the lower resolution
image is produced as described above with respect to FIG. 63.
[0410] In step 6630, the brightened image is forwarded for image
compression.
[0411] In step 6632, the brightened image and extracted plate image
are compressed.
[0412] In step 6634, the compressed brightened whole vehicle image
and plate image are stored in an appropriate storage medium.
[0413] Although the above example focuses on the processing of one
original whole vehicle image taken at one image resolution and one
vehicle image taken at a higher resolution (and, preferably, at a
different exposure setting) for the purposes of extracting a plate
image, it is contemplated that multiple low resolution and/or high
resolution images of a passing vehicle can be captured and
processed according to the appropriate steps outlined in FIG. 66
for the type of image captured. Thus, for example, in addition to
capturing at least one low resolution vehicle image, system 6500
may be configured to produce two high resolution images of each
passing vehicle to ensure that at least one extracted plate
intensity has an appropriate level, as described above.
[0414] Additionally, it is contemplated that the procedures
described above for embodiments of the present invention can be
used in combination. For example, a capture unit might initially
employ multiple capture positions to take multiple images of a
passing vehicle at a first camera exposure setting. Subsequently,
the plate location module processes one or more of the images taken
at the first exposure setting, and sends a signal to the capture
unit indicating the plate intensity data is not in a targeted
range. Finally, the capture unit takes further images of the same
passing vehicle at a second exposure setting adjusted based on the
set of intensities received from the plate location module.
[0415] In additional embodiments, an enforcement system extracts
only a plate region at an original resolution from a whole vehicle
image while discarding the rest of the image rather than capturing
and preserving a downsized image. This is useful in the case where
system 5800 is employed only for a license plate study where other
identifying vehicle information need not be preserved.
[0416] Furthermore, it is contemplated that embodiments of the
present invention can be used to track and identify vehicles in
areas other than tolling areas, such as parking lots, or
predetermined locations on public streets. In exemplary
embodiments, the system of the present invention can be triggered
to capture vehicle information such as a license plate whenever a
vehicle passes a point of interest. Such information could be used
for law enforcement or public safety purposes.
Multilane Vehicle Information Capture
[0417] Aspects of the ferromagnetic induction loop sensor systems
of the present invention can additionally be implemented in systems
and processes for multilane vehicle information capture (MVIC).
MVIC is an alternative approach to conventional transactions
conducted with vehicles traveling along roads, where the term
"road" includes multilane highways, toll plazas, bridges, tunnels,
parking lots, and other vehicle traffic locations. These
conventional transactions include toll collection at toll booth
stations or in an open road environment using manual or RF-tag
collection; vehicle identification using license plate image
capture; vehicle detecting using loop sensors, and other methods of
vehicle detecting. In a preferred embodiment of the present
invention, a vehicle information collection process is completely
automatic without use of human intervention, such as a toll
attendant, for collecting tolls. In one aspect, vehicles traveling
on multilane highways can be classified accurately using induction
loop sensors of the invention and appropriately charged tolls to
respective RF transponders placed on each vehicle. Preferably,
vehicles do not have to stop or slow down in a lane to pay tolls.
Preferably, vehicle information capture operates without requiring
vehicles to move in a confined lane, so that, for example, during
toll collection or other information capture, vehicles can straddle
between lanes as typically occurs in an open road environment.
Preferably, the MVIC system has the ability to capture a first type
of information about a vehicle in order to determine if further
information (or data) capture is required. In some embodiments, the
MVIC system can send a trigger to a VICU if it determines based on
initial data collection, that further vehicle data capture is
needed. For example, the MVIC system has the ability to detect
vehicles that do not have RF toll transponders passing through a
tolling area, and to alternatively capture an image of the license
plate of such vehicles. Preferably, the captured license plate
information can then be used to record payment of users that are
registered to pay toll based on their vehicle license plate ("pay
by plate") or to send the plate information to a toll violation
enforcement system for users that are not paying by means of an RF
transponder or vehicle license plate.
[0418] Embodiments of the present invention utilize multiple
intelligence units or subsystems to overcome current problems that
are associated with multilane vehicle information capture in an
open highway environment. In general, desirable features for an
multilane vehicle information capture system include the following:
[0419] 1) Ability to classify vehicle axles accurately and charge a
vehicle transponder appropriately in the case of RF toll
operations; [0420] 2) In case of vehicles not having RF
transponders, ability to capture a vehicle image that can be used
for the purposes of collecting toll payment or to send the image to
a violation enforcement system. [0421] 3) Ability to capture
vehicle images for pay by plate transactions; [0422] 4) Ability to
perform general data capture operations to collect vehicle
information that can be used for the purposes of surveys,
statistical traffic information, and the like; [0423] 5) Ability to
provide appropriate system failure notifications; and [0424] 6)
Stability and accuracy of the system.
[0425] There are many problems associated with conventional open
road tolling (ORT) systems. One of the most significant problems
involves the identification of a vehicle that is located in
multiple lanes (e.g., a vehicle that straddles more than one lane).
When a vehicle straddles more than one lane, the toll system may
fail to capture the vehicle for purposes of paying the toll,
misassociate the paying customer with the wrong vehicle, or over-
or under-count vehicle axles for the purposes of data capture.
Another common problem is the inability of the system to properly
manage multiple transactions occurring at about the same time and
involving multiple vehicles in close proximity. For example, the
following scenario representing a series of transactions that are
difficult to manage may occur frequently: identify a first vehicle
that has a toll transponder (tag); capture payment from the toll
tag; associate the captured payment with the first vehicle;
simultaneously identify a second nearby vehicle that did not pay by
toll tag; and capture a license plate image of the second vehicle,
the latter step followed by charging of payment for those vehicles
authorized to pay be license plate, or sending the plate image of
non-authorized vehicles to a toll enforcement system. These
problems limit usefulness of conventional open road tolling
schemes.
[0426] The present invention utilizes multiple intelligence units,
or subsystems, to overcome current existing problems that are
associated with toll collection in an open highway environment. In
a preferred embodiment, the subsystems include an intelligent
vehicle identification system (IVIS), an RF system, and a vision
tacking system (VTS). The MVIC system of the present invention
operates to consolidate intelligence obtained from the multiple
subsystems.
[0427] FIG. 67 illustrates components of an multilane vehicle
information capture system according to an exemplary embodiment of
the present invention. MVIC system 6700 includes an multilane
vehicle information capture (MVIC) central unit 6702, that acts as
the central processing unit for MVIC system 6700. It is responsible
for gathering information from the various subsystems 6704-6710
discussed individually below. Control unit 6702 consolidates input
data received from the subsystems to make decisions about toll
transactions, including a determination of a vehicle position and
an associated transponder.
[0428] In the embodiment illustrated in FIG. 67, system 6700
includes IVIS 6704 that includes IVIS sensors that preferably
comprise ferromagnetic induction loops. However, in other
embodiments, IVIS 6704 can be replaced by any other type of vehicle
sensor, such as a loop sensor, that can detect a vehicle's presence
in a roadway. When a vehicle passes through an embedded roadway
containing IVIS sensors, IVIS system 6704 reads many times per
second (e.g., about 333 times/sec) to determine a vehicle position
with respect to the sensors. IVIS system 6704 logs various types of
information such as axle entry/exit times using sensors as
described above, as well as axle amplitudes generated by vehicle
tires on the sensors. All this information is then transmitted to
MVIC unit 6702 for further processing to determine, for example,
the vehicle position.
[0429] System 6700 includes VTS 6706 that collects information
about a vehicle position when the vehicle passes through vision
tracking sensors included in the VTS. This information is
transmitted to MVIC central process unit 6702 for further
processing.
[0430] System 6700 contains RF System 6708 that reads a properly
mounted transponder in a side of the vehicle multiple times per
second (e.g., about 90 to 300 times/sec) when the vehicle passes
under an antenna located in system 6708. Typically, in tolling
applications, where RF systems are used, an RF system reads only
one time from a vehicle transponder and subsequently puts the
transponder in a "sleep" mode to avoid cross-reads for that
transponder from adjacent lanes. A cross-read occurs when a
transponder is read by a system in a lane other than where the
vehicle containing the transponder is traveling. RF system 6708 of
the present invention differs in operation from this typical
approach. Rather, system 6708 is configured to perform transponder
reads as many times as possible, including cross-reads, late reads,
and early reads. The latter two types of reads occur when a
transponder is read after or before, respectively, a vehicle is in
a proper area for conducting a "normal" RF read. The later reads
are problematic for a conventional RF system, that may assign late
reads to trailing vehicles, and early reads to leading vehicles,
rather than the vehicle of interest. RF system 6708 passes the read
data to MVIC unit 6702.
[0431] Lane Controller (LC) Unit 6710 of system 6700 is responsible
for sending appropriate transactions to a database unit 6712. LC
6710 receives necessary information from MVIC central process unit
6702 for generating a unique transaction for each vehicle.
[0432] Database Unit (DB) 6712 is responsible for storing
transaction information sent by lane controller 6710. Such
information is used for revenue collection and audit purposes, as
well as for generating reports and/statistics related to vehicle
transactions.
[0433] System 6700 additionally includes VICU 6714 that is
responsible for capturing vehicle images whenever a trigger source
such as central process unit 6702, IVIS 6704, or another loop based
triggering device (not shown) triggers a VICU camera. Exemplary
operation of a VICU in a toll violation enforcement system is
described above in detail. Preferably VICU 6714 contains at least
one camera for capturing vehicle images, and is configured for
storing the captured images with a proper file name associated with
a vehicle transaction and sent by MVIC central process unit 6702.
In exemplary embodiments, VICU 6714 additionally comprises a
program running in a processing unit, such as program 5810
described above that contains individual image processing and
exposure modules to ensure that a clear image of a violating
vehicle and license plate are obtained.
[0434] In an open highway environment, VICU 6714 may be activated
under one of several circumstances. For example, in an MVIC
environment, certain vehicle travel lanes may be reserved for
vehicles equipped with RF transponders to automatically record
tolling transactions. Vehicles without transponders may be required
to travel in other lanes that are equipped with conventional toll
collection facilities. Therefore, a transponderless vehicle
traveling in a reserved lane may be flagged as a potential
violator, triggering VICU 6714 to capture vehicle images of the
passing vehicle. Additionally, a vehicle equipped with a
transponder that indicates insufficient funds within an account to
pay a toll can be flagged as a potential violator. The vehicle
information, for example, a license plate image, can then be used
to assess a payment if the vehicle is registered for pay by plate,
or it can be forwarded to a violation enforcement system.
[0435] In alternative embodiments, VICU 6714 is configured to
remain active and can capture images of each passing vehicle.
Accordingly, system 6700 can determine a time subsequent to a
vehicle passing an MVIC site, that a transaction record associated
with the vehicle passing the tolling site indicates the vehicle is
a toll violator or needs to pay by license plate, if applicable.
For example, it may be determined that an account associated with
the vehicle's transponder did not authorize payment of the toll
charge. System 6700 can then retrieve from VICU 6714 an image to
assist in identification of the vehicle, which is then forwarded to
a violation enforcement system of pay by plate collection
system.
Summary of Operation of MVIC Components
[0436] RF System
[0437] In embodiments of the present invention, RF system 6708 is
configured to obtain multiple reads from a passing vehicle.
Accordingly, as described in more detail below, problems in
conventional systems, such as cross lane reads (cross-reads),
advanced reads, skipped reads, or late reads are not as paramount.
FIG. 68 illustrates aspects of RF system 6708 according to an
exemplary embodiment of the present invention. In the example shown
in FIG. 68, system 6708 comprises a gantry 6802 that is configured
to overhang multiple travel lanes in a roadway. For the purposes of
clarity, in this and following FIGS, embodiments of the present
invention are presented with reference to two or three lane
environments. However, it will be understood that system 6700 is
generally applicable to operate in multilane environments, where
the number of lanes can be up to 10 or more, and the number of
components of subsystems 6704, 6706, 6708, 6710, and 6714 that are
used to capture vehicle information and communicate with vehicles
in different lanes will scale accordingly. For example, the number
of gantry 6802 includes RF antenna 6804 and RF antenna 6806. Each
antenna when operational creates a read zone, denoted as zones 6808
and 6810. Also illustrated in FIG. 68 are IVIS components including
sensors 6812 and 6814, discussed further in the following section,
and square sensors 6815. Sensors 6812 and 6814 are preferably
gradient sensors. Sensors 6815 are preferably square sensors. Each
read zone is constructed to read a passing vehicle with a
transponder as it travels in its respective lane associated with
the read zone. In addition, the read zones overlap, in a straddle
region 6816 wherein a vehicle traveling in either lane may be read
in both read zones, depending on the exact vehicle trajectory.
[0438] In an multilane open road environment, meaning that there
are no barriers between multiple lanes, a car may travel outside of
the center of a painted tolling lane. The car may cross between
lanes, it may straddle lanes, or travel in the road shoulder. For
example, when entering a zone for automatic tolling in an MVIC
environment, it may enter the zone with vehicle placement at a 60
to 40 ratio (or 60-40) between two adjacent lanes, and subsequently
cross under an RF antenna gantry used for reading a vehicle
transponder at a 50-50, 70-30 or 90-10 ratio. Instead of reading
the transponder one time and inducing a sleep mode, RF system 6708
provides overlay reading zones 6808 and 6810 so that the reading
zones overlap in straddle region between adjacent lanes, enabling a
user of the invention to ensure that an antenna read of the
transponder occurs in straddle zone 6816 as well as in the center
of a lane.
[0439] Preferably, RF system 6708 continuously reads the vehicle
transponder as rapidly and frequently as possible. In a preferred
embodiment, RF system 6708 employs multiple antennas 6804, 6806 on
gantry 6802 to read a transponder of a passing vehicle, so that
information from the multiple antenna reads can be used to
determine where the vehicle is located. As is known, transponders
vary in the rate that they can be read. Some perform as slowly as
96 times/sec while others perform as rapidly as 333 times/sec. In
an exemplary embodiment, both RF read zones 6808, 6810 are roughly
10 feet long, such that, if a vehicle is traveling in the center of
a lane at 60 mph, the vehicle moves at approximately one inch per
millisecond. The read zone (120 inches) is thus traversed in about
one tenth of a second, so that using a 333 times per second sample
rate, roughly 30 reads can be performed as the vehicle traverses
the read zone of a particular lane.
[0440] Using multiple reads of a passing vehicle, RF system 6708
can provide information to determine the vehicle position with
respect to a given lane. For example, if a successful read count of
a vehicle transponder of 20 to 30 times is obtained using an
antenna associated with a first lane; and in a second, adjacent
lane a read count of 5 is obtained; and in a third lane (not
shown), nearby, 2 reads are obtained, the vehicle can be
definitively located in the read zone associated with the first
lane. In another scenario, if the vehicle straddles the first lane
and second lane with a 70-30 ratio with respect to vehicle
placement in the respective lanes, denoted by position A, 20 reads
may be obtained in zone 6808 associated with the first lane, and 10
reads in zone 6810 associated with the second lane. Therefore,
using only the information obtained from RF system 6708, system
6700 can determine that the vehicle is approximately located
straddling the first and second lanes with a 70-30 ratio of vehicle
placement. If, in another scenario, the vehicle were to exactly
straddle the lanes at a 50-50 ratio, traveling through highway
region 6816 at position B, the read zones associated with each lane
would generate approximately the same number of reads. In the later
scenario, depending on the exact configuration of RF read zones,
the total number of reads generated for the vehicle transponder may
be less than for travel through a lane center (for example, the
total of successful reads may be 15 in the latter case, as opposed
to 30 in the center lane case); however, the amount of reads is
still sufficient to accurately locate the vehicle.
[0441] In contrast, current art using RF technology for toll tag
reading was developed based on single lane applications. Efforts
centered on obtaining information only from a read zone in a single
lane, so that reading from an adjacent lane is eliminated, as well
as early or late vehicle reads. This was compelled by the fact that
the current technology used for toll tag reading is back scatter
technology where a toll tag is polled and broadcasts its energy in
all directions. The potential exist greatly for a tag to be read in
an adjacent lane, because the RF radiation is reflected off
vehicles and off different shapes at varying angles. When an RF
backscatter system conducts a vehicle tag read, it broadcasts an RF
signal from an antenna, which is then backscattered from the tag in
every direction. So, attempts in the current art have predominantly
involved focusing the RF radiation energy into a small region in
the center of the lane in an effort to avoid reading in an adjacent
lane. This focusing helps avoid reading in an adjacent lane that
can cause a customer in the wrong lane to be treated as a violator,
for example.
[0442] Another potential problem overcome by the present invention
is the inadvertent charging of a vehicle that is read in two
different lanes for both lanes. This might occur, for example due
to cross-lane reads. This has further reinforced the practice in
current technology to focus RF energy only in one lane, conduct a
single read, put the RF tag to sleep, and avoid reading a car
early, so that reads are not inadvertently conducted on a wrong
car. Thus, a tag on a passing vehicle is read only one time
allowing only one time to collect money. This technology works well
in a stop-and-go or slow traffic speed, single lane environment.
However, in a location where there are no barriers between multiple
lanes of tolling all in one area, it becomes much more difficult to
identify which vehicle paid a toll and where the read actually is
located.
[0443] Another common industry practice to attempt to eliminate
cross-lane reads is to use what is known as time division
multiplexing. Such technology alternately turns on an antenna in a
first lane to collect a toll, while turning off adjacent antennas.
If the antenna generates a single read, it is identified with the
car traveling in the first lane. However, the potential for
cross-lane reads still exists. A car straddling lanes could avoid
payment if an antenna of the wrong lane is activated, and a paying
customer could be deemed a violator.
[0444] By conducting multiple reads, system 6708 provides the
ability to minimize all the above-mentioned problems with the
current art. A more precise location of a vehicle is generated, the
possibility of mistaking one vehicle for another nearby based on a
single read is reduced, and lane straddlers do not avoid
payment.
[0445] IVIS System
[0446] In exemplary embodiments of the present invention, IVIS 6704
comprises vehicle detection sensors, e.g., inductive loop sensors
as depicted in FIG. 68 that enable system 6700 to accurately
classify vehicles, count axles, calculate speed, measure vehicle
length and classify vehicle type. Preferably, collecting of
information from IVIS 6704 is synchronized with RF tag reads
conducted by system 6708 to further enhance the ability to identify
an appropriate vehicle with an RF tag, and an appropriate vehicle
that does not have an RF tag.
[0447] By synchronizing information obtained from IVIS 6704 and RF
system 6708, the likelihood of failing to identify a vehicle is
greatly reduced. For example, using RF reading to count the number
of tag reads and determining the entry point of a vehicle at an
IVIS sensor, the entry time of a vehicle into an RF read zone can
be calculated, so that the time when tag reads should begin and end
can be accurately determined, if the vehicle has an RF tag. As
described above, an IVIS system based on ferromagnetic loop sensors
containing, among others, gradient sensors, can accurately
determine the spacing between two axles of a vehicle. In a majority
of vehicles, an RF tag is located in the front one-third of that
spacing between the axles. By knowing where the RF read zone is
located on the earth compared to the RF read antenna, one can then
determine the approximate time that the tag reads should start and
stop, as discussed further below.
[0448] Use of RF system 6708 in conjunction with IVIS system 6704
provides further advantages in identifying a vehicle in an open
road multilane environment. By knowing when a vehicle transponder
should enter RF read zone 6808, for example, using IVIS gradient
sensor 6814, and conducting continuous reads (continuously
sampling) of the RF transponder during the time when the vehicle is
read zone 6808, accurate marrying of IVIS data and RF data
generated by the passing vehicle assures that a correct
identification is made. This also increases the likelihood of
identifying vehicles that do not have an RF tag since the system
can determine if no RF reads are successful during the time in
which the vehicle should be in the RF read zone.
[0449] In preferred embodiments, MVIC system central processor unit
6702 gathers all information sent by the subsystems including IVIS
6704, VTS 6706, and RF system 6708. The vehicle position can be
partially determined based on the vehicle and/or vehicle axle
entry/exit times on IVIS gradient sensors. IVIS 6704 is also
capable of calculating a speed of the vehicle based on the
entry/exit times of a vehicle and/or vehicle axle on the gradient
sensors. IVIS 6704 can use this speed to calculate the axle spacing
of the vehicle. All this information is subsequently sent to MVIC
central process unit 6702.
[0450] MVIC central process unit 6702 also receives transponder
data from RF system 6708. As further depicted in FIG. 68, RF
antennas 6804 and 6806 are laid out in such way that each RF read
zone for a vehicle transponder of a vehicle traveling in a given
lane matches closely the position of a respective IVIS sensor
layout. Preferably, the MVIC system of the present invention
adjusts an RF antenna's angle to cover about 80% of the roadway
region that is covered by a respective IVIS sensor layout,
providing for optimum synchronization of IVIS sensor data with RF
sensor data. This synchronization is important because MVIC-RF
system 6708 of the invention allows cross/early/late reads of the
transponder.
[0451] In an exemplary embodiment of the present invention depicted
in FIG. 69, an additional set of lane straddling sensors 6902,
6904, 6906 are added to IVIS system 6700. These lane straddling
sensors may be configured to be part of IVIS 6704. Lane straddling
sensors of the invention, such as sensors 6902, 6904, 6906 can have
one of a number of shapes including square, circular, oval,
rectangular, and other shapes. Preferably lane straddling sensors
are configured as "diamond" sensors, that is, they assume a diamond
shape as viewed in the direction of travel. Lane straddling sensors
6902, 6904, 6906 provide advantages over conventional loop
configurations in determining vehicle position. In conventional
inductive loop technology; if a sensor is placed in a normal manner
in a roadway, a field of the sensor for a 6 by 6 (or 6.times.6)
size, extends approximately 3 feet outside the sensor. The present
inventors have determined that for fields of inductance, the
diameter of the field is reduced at corners of a loop. Therefore,
by turning a square loop about 45 degrees to the roadway travel
direction, and placing the loop at positions that straddle the
border between lanes and other lanes or shoulders, a vehicle
position can be more accurately determined. For example, if a
vehicle is going through the center of lane 6908, lane straddling
sensors 6902, 6904 will be activated at approximately the same
time. If the vehicle is straddling between lanes 6908 and 6910,
only lane straddling sensor 6904 will be activated at one time.
[0452] In exemplary embodiments of the present invention, system
6700 collects information including activation information obtained
from lane straddling sensors, vehicle axle spacing, arrival time
and departure time of the vehicle and/or vehicle axles in each
lane, speed of the vehicle, and length of the vehicle all obtained
from other sensors of IVIS system 6704, so that the information can
be compared to determine the status of multiple vehicles occupying
adjacent lanes.
[0453] For example, if RF data collected based on the amount of RF
reads in adjacent lanes indicates a first vehicle is a straddler,
and IVIS lane straddling diamond sensors indicate the vehicle is a
straddler, and additional data such as vehicle speed, arrival and
departure information, and axle spacing indicate it is a straddler,
then system 6700 can determine which of a plurality of cameras of
VICU 6714 to employ to record a car that did not pay by RF tag, and
which of multiple vehicles in close proximity to appropriately
allocate the payment of a toll. In exemplary embodiments, either RF
tracking system 6708 or IVIS 6704 can be solely used to identify a
straddler with a high degree of accuracy. But in a preferred
embodiments, by concurrent use of any combination of RF tracking
system 6708, IVIS 6704, as well as Vision tracking system 6706,
MVIC system 6700 performs more accurately as a multilane vehicle
identification system.
[0454] In the following sections, operation of an MVIC system
according to exemplary embodiments of the present invention is
discussed in further detail.
[0455] FIG. 70 depicts a situation in which MVIC arrangement 7000
is used to detect vehicle 7002 that straddles two travel lanes
7004, 7006, according to an exemplary embodiment of the present
invention. Vehicle 7002 straddles equally adjacent lanes 7004, 7006
while located over sensors 7008, 7010, and 7012, each located in
both lanes depicted. Vehicle 7002 also is located within RF read
zones 7014, 7016 of lanes 1 and 2, respectively. Referring again to
FIG. 67, tolling arrangement 7000 can be included, for example, as
part of MVIC 6700, such that information is transmitted to MVIC
unit 6702 when vehicle 7002 passes through arrangement 7000. In the
scenario depicted in FIG. 70, vehicle 7002 may have entered
arrangement 7000 entirely in lane 7004 or 7006, or partially
straddling the two lanes.
[0456] As vehicle 7002 travels through arrangement 7000, MVIC unit
6702 receives vehicle information from IVIS sensors 7008, 7010,
7012 as well as RF read zones 7014, 7016. Vehicle information such
as vehicle speed, axle spacings, axle amplitudes and entry/exit
times of the vehicle axles on sensors 7008, 7010 of both the lanes
are forwarded to unit 6702. FIG. 71 displays a typical gradient
sensor result showing frequency vs time for a two axle vehicle,
illustrating the appearance of two peaks corresponding to
individual axles, as discussed in detail above.
[0457] MVIC central process unit 6702 also receives RF data for the
vehicle (if a transponder exists in the vehicle) from RF (AVI)
system 6708, using antennas 7018 over respective lanes 7004,7006.
Gantry 7019 is configured to contain a plurality of an antennas.
Preferably, the location of antennas 7018 on gantry 7019 is such
that an antenna is placed over each travel lane. Preferably
antennas 7018 in both lanes 7004, 7006 try to read the same vehicle
transponder (not shown) as many times as possible, and forward the
read information to MVIC unit 6702. MVIC central process unit 6702
consolidates all these data to make an accurate determination of
the position of vehicle 7002.
[0458] MVIC central process unit 6702 also receives data from
diamond-shaped lane straddling sensors 7020a, 7020b, 7020c that are
positioned to straddle their respective lanes, as depicted in FIG.
70. Information received from the latter sensors is used to make a
final decision on the vehicle position with respect to lanes, as
described further below.
[0459] FIG. 72 illustrates steps in a method for determining a
vehicle position using IVIS and RF data, according to an exemplary
embodiment of the present invention. In step 7200, information
received from IVIS 6704 and RF 6708 systems is stored in two
different databases. For example, as vehicle 7002 travels through
arrangement 7000, both IVIS and AVI systems, as well as lane
straddling sensors 7020a, 7020b, 7020c can detect the vehicle
position. The information received preferably includes data
collected from respective inductive loop arrays and RF read zones
in each of lanes 7004, 7006.
[0460] At step 7202, if central process unit 6702 determines that
vehicle entry/exit times are not reported from sensors 7008, 7010
of both travel lanes, then the process moves to step 7204, where
unit 6702 makes a tentative decision that vehicle 7002 is not
straddling as per determination by IVIS 6704. The process then
moves to step 7222.
[0461] If entry/exit times are reported by sensors 7008, 7010 in
both lanes, then the process moves to step 7206, where a difference
in entry/exit times between that recorded for lane 7004 and 7006 is
calculated. This time difference is then used to assess whether the
data likely reflects detection of one vehicle or two vehicles. For
example, at a highway speed of 60 mph, a vehicle may traverse an
average car length of 15 feet in about 125-150 milliseconds.
Therefore, if IVIS arrays in neighboring lanes report differences
in vehicle entry times that are less than the calculated time to
travel such a distance, it can be assumed that the recorded times
are from the same vehicle, since two vehicles cannot occupy the
same space at the same time. If a value of entry time discrepancy
greater than such a calculated value is recorded, it increases the
likelihood that two vehicles are present.
[0462] In step 7208, in the embodiment shown, if central process
unit 6702 determines that vehicle entry/exit times reported from
adjacent lanes are greater than 125 milliseconds, the process moves
to step 7210 where a tentative decision is made that the data
received comes from two vehicles, and vehicle 7002 is not lane
straddling. The process then moves to step 7222. If a difference in
entry times less than 125 milliseconds is reported, the process
moves to step 7212.
[0463] In step 7212, if central process unit 6702 determines that
data collected from IVIS sensors in both lanes does not correspond
to a same range of vehicle speed, the process moves to step 7214,
where a tentative decision is made that vehicle 7002 is not lane
straddling. The process then moves to step 7222. If a same range of
vehicle speed is reported form IVIS sensor data of both lanes, then
the process moves to step 7216.
[0464] In step 7216, if central process unit 6702 determines that
the number of vehicle axles and axle spacing recorded from IVIS
data reported from both lanes does not agree, then the process
moves to step 7218, where a tentative decision is made that vehicle
7002 is not lane straddling. The process then moves to step 7222.
If axle number and axle spacing data collected from IVIS sensors in
both lanes agrees, then the process moves to step 7220 where
central process unit 6702 makes a partial decision that vehicle
7002 is lane straddling according to IVIS data.
[0465] In step 7222, central process unit 6702 retrieves RF data
reported from a transponder on vehicle 7002. If central process
unit 6702 determines that RF data corresponding to vehicle 7002 is
not reported from both RF read zones the process moves to step
7224, where a tentative decision is made that vehicle 7002 is not
lane straddling. The process then moves to step 7234. If central
process unit 6702 determines that RF data corresponding to vehicle
7002 is reported from both RF read zones the process moves to step
7226.
[0466] In step 7226, unit 6702 calculates the number of RF reads
obtained from each RF read zone 7014, 7016.
[0467] In step 7228, if central process unit 6702 determines that
the number of RF reads received from read zone 7014 differs widely
from that received from zone 7016, the process moves to step 7230.
In step 7230 a tentative decision that vehicle lane straddling by
vehicle 7002 did not occur is made. The process then moves to step
7234.
[0468] If central process unit 6702 determines that the number of
reported transponder reads in zone 7214 is close to the
corresponding number in zone 7216, the process moves to step 7232.
Because the number of reported reads in neighboring lanes is close,
it is determined that vehicle 7002 is lane straddling as determined
by system 6708. The process then moves to step 7234.
[0469] Referring now to FIG. 73, at a point of time subsequent to
that depicted in FIG. 70, vehicle 7002 passes through a roadway
region containing lane straddling sensors 7020a, 7020b, 7020c. The
presence of vehicle 7002 is detected by at least one lane
straddling sensor and forwarded to MVIC central processing unit
6702. In a preferred embodiment of the present invention, the size
of lane straddling sensors 7020a, 7020b, 7020c is such that at
least one sensor is always activated when a vehicle traveling in a
highway lane of width in the normal range for highways passes by
the lane straddling sensors. Preferably, a width of lane straddling
sensors is about 6 feet as described above. As also discussed
previously, a lane straddling sensor having a diamond shape
minimizes the possibility of cross talk between two adjacent lane
straddling diamond-shaped sensors, as opposed to square or
rectangular shaped sensors.
[0470] As evident from FIG. 73, lane straddling sensors 7020a,
7020b, 7020c are laid along lane borders in such a way that vehicle
7002 activates a different number of lane straddling sensors
depending on its exact position within a lane or lanes. In the case
illustrated in FIG. 73, where vehicle 7002 is straddling equally
between two lanes 7004, 7006, only middle lane straddling sensor
7020b, that also straddles the two lanes, is activated.
[0471] Referring again to FIG. 72, at step 7234, central process
unit 6702 retrieves data reported from lane straddling sensors
7020a, 7020b, 7020c. Unit 6702 checks to see how many of the
sensors were activated at the time vehicle 7002 passed arrangement
7000.
[0472] In step 7236, if it is determined that activation occurred
from other sensors in addition to middle sensor 7020b, then the
process moves to step 7238 where a determination is made that
vehicle 7002 was not straddling lanes. If only sensor 7020b
reported activation, then the process move to step 7240 where
vehicle 7002 is tentatively deemed to be straddling lanes 7004,
7006 based on lane straddling sensor data. Based on the above
approach, the MVIC system makes a final determination as to whether
vehicle straddling has occurred. Depending on the agreement or lack
of agreement between the tentative determinations of straddling
from data received from "subsystems" (the subsystems comprise in
the case of FIG. 72: 1. IVIS sensors 7008, 7010, 7012; 2. RF AVI
antennas 7018, and; 3. IVIS lane straddling sensors 7020a, 7020b,
and 7020c), the final determination can be more or less certain.
For example, if data from all subsystems is in agreement, then a
firm final determination of straddling or not straddling is made
with a very high confidence level.
[0473] FIG. 74 illustrates a scenario in which two vehicles 7402,
7404 pass through arrangement 7000 in two adjacent lanes 7004,
7006, respectively, at the same time. In the scenario illustrated,
arrangement 7000 first senses the vehicles' presence using RF read
zones 7014, 7016 and IVIS sensors 7008, 7010, 7012. At the instant
illustrated in FIG. 74, the two vehicles are side-by-side and
passing through respective regions of lanes 7004, 7006 containing
lane straddling sensors 7020a, 7020b, 7020c. Vehicles 7402 and 7404
are located entirely within their respective lanes, 7004 and 7006.
In this case, vehicle 7402 activates lane straddling sensors 7020a
and 7020b, while vehicle 7404 activates lane straddling sensors
7020b and 7020c. Thus, unit 6702 determines that all three lane
straddling sensors illustrated are activated. Based on the fact
that a normal-size vehicle width is less than a lane width, unit
6702 knows that one vehicle can activate at most two lane
straddling sensors. Accordingly, system 6700 determines that more
than one vehicle are present at the same time in arrangement
7000.
[0474] FIG. 75 illustrates exemplary steps employed in a method for
determining the simultaneous presence of more than one vehicle in
an MVIC area using lane straddling sensors, according to an
exemplary embodiment of the present invention. In step 7502,
central process unit 6702 checks to determine how many lane
straddling sensors in two contiguous lanes have been activated.
Preferably, the lane straddling sensors are diamond shaped.
[0475] In step 7504, central process unit 6702 determines if more
than one sensor reports activation. If not, the process moves to
step 7506 where a determination that only one vehicle is present
and is straddling lanes, as illustrated for vehicle 7302 in FIG.
73. If more than one sensor reports activation, the process moves
to step 7508.
[0476] In step 7508 central process unit 6702 determines if more
than two sensors report activation. If not, the process moves to
step 7510.
[0477] In the steps to follow, three different scenarios where only
two sensors are activated can be distinguished. In a first scenario
illustrated in FIG. 76, vehicle 7602 travels entirely within lane
7006 and activates two sensors, 7020b and 7020c. In a second
scenario illustrated in FIG. 77, vehicles 7702 and 7704 each travel
directly over only one lane straddling sensor, 7020a and 7020c
respectively, such that only two lane straddling sensors in total
are activated. A third set of scenarios in which two cars traveling
through adjacent lanes that only trigger two lane straddling
sensors to activate include the scenario of FIG. 78, in which
vehicles 7802 and 7804 travel directly over adjacent sensors 7020b,
7020c, respectively. Similarly, if instead of over 7020c, vehicle
7804 were placed over sensor 7020a, only two sensors would
activate.
[0478] In step 7510, central process unit 6702 determines whether
the two sensors activated are adjacent. If not, then the process
moves to step 7512 where it is determined that two vehicles are
present and each is straddling a lane, as illustrated in FIG.
77.
[0479] If adjacent sensors area activated, then the process moves
to step 7514. In step 7514, unit 6702 checks other IVIS sensor data
and RF data reported for the same transaction or time period from
arrangement 7000. Using the other IVIS sensor and RF data, a
determination is made as to whether the two adjacent lane
straddling activation reports represent a single vehicle traveling
entirely within a lane, as in FIG. 76, or two vehicles as in FIG.
78. The scenario involving two adjacent lane-straddling vehicles
passing over the lane straddling sensors also implies the vehicles
likely were adjacent while in RF read zones 7014, 7016.
Accordingly, as discussed above, unit 6702 can determine based on a
distribution of RF read counts for a given vehicle transponder that
the scenario of two lane straddling is present, rather than a
single vehicle in the center of a single lane. The latter scenario
would produce as single more narrow peak in RF read counts
representing the region in a lane or lanes through which the
vehicle traveled; while the former scenario would produce a broader
peak or even two separate peaks in RF read counts over a group of
lanes, representing the positions of two distinct vehicles.
Additionally, the total amount of successful RF reads over a group
of nearby lanes would be higher in the case of two adjacent
vehicles.
[0480] If three lane straddling sensors report activation, the
process moves to step 7516, where a tentative determination is made
that two vehicles are present. The process then moves to step 7518
to confirm the determination using other IVIS and RF data.
[0481] RF Read Zone Prediction Technique
[0482] Other embodiments of the present invention employ accurate
synchronization of data gathered from different subsystems, such as
IVIS 6704, VTS 6706, and RF system 6708, to track and identify
vehicles in an MVIC environment. FIG. 79 illustrates steps for
implementing a "read zone prediction" process to accurately
identify a vehicle, according to an exemplary embodiment of the
present invention.
[0483] In step 7902, a point at which a vehicle transponder enters
an RF read zone is determined. Referring to FIG. 70, the extent RF
read zones 7014, 7016 can be varied by changing the RF power from
antennas 7018 and also by changing an antenna angle, the latter of
which causes changes in RF read zone size at a given power. RF read
zone dimensions can be defined as that portion of space in which RF
power projected from an antenna is sufficient to conduct a read on
a passing transponder. As viewed in FIG. 70, a two dimensional RF
read zone is shown for each antenna 7018. In three dimensions an
actual RF read zone can roughly assume a shape of a cone. Knowledge
of approximate height above a roadway surface for transponders in
typical vehicles traveling in lanes 7004, 7006, as well as the
relative position of the transponder on a vehicle can then be used
to estimate at what point along a direction of traffic flow, a
transponder on a vehicle will enter the RF read zone cone.
[0484] FIG. 80 depicts a side view of a portion of arrangement
7000, where vehicle 8002 contains transponder 8004. As vehicle 8002
travels within lane 7004 (see FIG. 70) through. RF read zone 7014
created by antenna 7018 on gantry 7019, for purposes of the RF
system communicating with its transponder, the vehicle effectively
enters read zone 7014 at point A and leaves at point B. Therefore,
a vertically projected point A' on a surface of the travel lane
represents a point at which RF read zone begins for a transponder
positioned directly over the point at a height h indicated. Thus,
as a reference point on the highway, point A' indicates the
position above which a vehicle transponder positioned at an average
height is first able to be read by RF antenna 7018.
[0485] In step 7904, a distance between an entry point of a vehicle
over a first IVIS reference point 7010 and the entry point of the
RF read zone is determined. In the example illustrated in FIG. 80,
this corresponds to the distance L1, which represents the physical
distance along the roadway from the point where a feature of
vehicle 8002 first travels over IVIS sensor 7010 (point C), and the
point A'. This distance is thus preconfigured by arrangement of an
RF read zone in conjunction with IVIS sensors.
[0486] In step 7906, an entry time T1 of a vehicle feature of
interest over an IVIS reference point in is recorded by IVIS system
6704. TI can correspond, for example, to a front edge of vehicle
8002 crossing over a first edge of sensor 7012 shown in FIG. 70.
Alternatively, in an exemplary embodiment of the present invention,
TI corresponds to a time at which front axle 8006 crosses over
first sensor 7010 at point C. TI data is collected and stored in
system 6700.
[0487] In step 7908, a speed VS of vehicle 8002 is measured by IVIS
array 7012, as described above.
[0488] In step 7910, a vehicle length and axle spacing for vehicle
8002 are measured by a loop sensor, such as sensor 7012.
[0489] In an exemplary embodiment, based on overall vehicle size
and axle separation, in step 7912 a projected horizontal distance
L2 between the front axle and transponder of vehicle 8002 is
calculated by central process unit 6702. Historically, for a
majority of vehicles, an RF tag is located in a front one-third of
a spacing between the axles. Thus, distance L2 represents an
estimate of a projected horizontal between distance tag 8004 and
front axle 8006, based in part on measurement of axle
separation.
[0490] In step 7914, a distance L=L1+L2 is calculated, which
represents the distance vehicle 8002 travels from the time the
vehicle feature of interest passes an IVIS reference point as in
step 7906, and when vehicle transponder 8004 enters RF zone 7014.
In an exemplary embodiment, the vehicle feature of interest is
front axle 8006, and IVIS reference point is sensor 7010 at point
C, which detects the front axle presence as it passes over point C.
Thus, after axle 8006 passes over point C, it travels a distance L1
to reach a point over point A', and continues distance L2 before
transponder 8004 is positioned over A' at the point of entry into
RF read zone 7014.
[0491] In step 7916, unit 6702 calculates an expected time of entry
TE, for vehicle transponder 8004 to enter zone 7014, TE=TI+L/VS.
Thus, system 6700 measures an initial vehicle entry time T1 as
detected by a loop sensor of IVIS array 8010, as well as speed and
axle spacing, and computes an estimated time TE when RF antenna
7018 can begin reading transponder 8004, based on a preconfigured
MVIC system distance L1 and estimated vehicle-based distance L2.
Similarly, with knowledge of the distance A-B, based on the
geometry of read zone 7014, an exit time TX can be calculated.
[0492] Referring again also to FIG. 70, in step 7918, central
process unit 6702 ensures that all RF antennas 7018 are
continuously reading so that vehicle multiple vehicle transponder
reads can be conducted as vehicle 8002 enters zone 7014.
Preferably, antennas 7018 are triggered to be continuously reading
before vehicle 7902 enters zone 7014.
[0493] In step 7920, unit 6702 records a time TRE in which a first
read of transponder 7904 is received.
[0494] In step 7922, antennas 7018 conduct continuous reads, such
that multiple RF reads of transponder 7904 are recorded as vehicle
7902 travels through RF read zone 7014.
[0495] In step 7924, central process unit 6702 records a time TRX
that a last RF read of transponder 7904 is recorded before no
further successful reads are received.
[0496] In step 7926, central process unit 6702 compares calculated
RF read zone entry time TE to actual recorded time TRE. Preferably,
a comparison between calculated and recorded exit times, TX and
TRX, is also made.
[0497] In step 7928, based on comparison of predicted entry and
exit times of vehicle transponder 8004 in zone 7014, central
process unit 6702 makes a determination as to whether the vehicle
detected by IVIS array 8010 corresponds to the RF tag read
subsequently.
[0498] Because multiple RF reads are conducted, a "time window" in
which vehicle 8002 enters, passes through, and exits read zone 7014
is created and can be preserved in a transaction record. The
precision of this window can be maximized by maximizing the rate at
which RF reads are conducted. Thus, if a vehicle passing through a
10 foot long RF read zone at 100 feet/second (.about.65 mph) is
read at a rate of 50 times per second, or every 20 milliseconds, it
can be expected to be read approximately 5 times within the 100
milliseconds it takes to traverse the read zone. However, a slight
variation in capturing a reflected signal from the transponder
might cause an actual number of reads to be 4 or 6, leading to some
uncertainty in actual entry and exit times. However, if the vehicle
is read at a rate of 330 times per second (once every 3
milliseconds) the three millisecond precision provides for the
vehicle to be recorded about 33 times, within the RF read zone. A
slight variation in the number of reads, from 32 to 34 reads, for
example, results in much less uncertainty as to actual vehicle
entry and exit times in the RF read zone.
[0499] In other embodiments, vehicle data collected from a VTS,
such as VTS 6706, can be synchronized with an RF read zone system,
either in conjunction with the IVIS system described above, or in
place of the IVIS system. This data can result in a VTS-based RF
read zone prediction. For example, a time can be recorded in which
a vehicle appears in an image captured by a VTS mounted near the RF
read zone. The time and relative position of the vehicle in the
image with respect to the RF read zone can then be used to
establish whether a vehicle toll tag measured in the RF read zone
is associated with the vehicle in question.
[0500] In a further exemplary embodiment of the present invention,
VTS 6706 is used in conjunction with IVIS 6704 to provide accurate
tracking of a vehicle in an MVIC environment. In FIGS. 81a-81d, a
series of images of a vehicle are recorded by a vision tracking
system arranged according to one embodiment of the present
invention.
[0501] FIG. 88 illustrates a "four diamond one VTS" configuration,
according to an embodiment of the present invention. Gantry 8802
contains camera 8804 and VTS light 8806. Camera 8804 is mounted
above a middle of a lane 8808, such that information gathered from
sensors 8810, 8812 that straddle lane 8808 can be coordinated with
VTS information gathered from camera 8804.
[0502] In another embodiment illustrated in FIG. 89, a "three
diamond one VTS" arrangement contains a VTS camera 8902 mounted
directly over a border between lanes 8904 and 8906, placing the
camera in line with a lane straddling sensor 8908.
[0503] FIG. 90 illustrates exemplary steps involved in a method for
vehicle tracking, according to an embodiment of the present
invention. In step 9002, a camera position of a VTS unit is
calibrated with respect to a coordinate on a road surface.
[0504] In step 9004, images of passing vehicles are captured by the
camera unit. Preferably, the images are captured continuously at a
predetermined frame rate.
[0505] In step 9006, the captured images are stabilized by
compensating for pixel movement caused by camera movement due to
gantry vibration during capture of the images.
[0506] In step 9008, a monitoring zone within the images is
established. The monitoring zone can comprise all or part of each
image.
[0507] In step 9010, moving objects are identified by analyzing the
series of captured and stabilized images within the monitoring
zone.
[0508] In step 9012, a segmentation process is applied to pixels,
such that all pixels identified as belonging to the same object are
grouped together.
[0509] In step 9014, a trajectory is extracted based on a relative
movement of a segmented object between predetermined captured
images.
[0510] In step 9016, a predicted trajectory is obtained for an
object during further movement within the monitoring zone.
[0511] In step 9018, vehicle trajectory information is reported to
a central process unit, for example unit 6702, in order to assist
in vehicle tracking.
[0512] In FIGS. 82a-82d, the results of motion analysis collected
for moving objects within a picture frame by VTS system 6706 are
displayed. A segmentation process groups all neighboring bright
pixels together to form a moving object, so that each moving object
corresponds to a moving vehicle. Area 8202, for example, contains
an image of vehicle 8204. Each figure displays an image of fixed
region 8206, where the successive images are taken at different
times. FIG. 83 displays images containing only area 8202 extracted
from FIGS. 82a to 82d, respectively. The images are superimposed on
the same frame to display their relative position within the field
of view. The arrow displays a calculated trajectory of vehicle 8202
during the time between images displayed in FIGS. 82a and 82d.
[0513] Such position-time trajectory output information can be
combined with IVIS straddle sensor information to determine whether
a vehicle is a straddler or not. For example, cameras of VTS 6706
can be mounted in close proximity to an IVIS sensor. Vehicle images
of a vehicle traveling in a lane of interest can be collected by
system 6706, forwarded to central process unit 6702, time stamped,
and stored in a record with vehicle information collected at the
same time from corresponding IVIS sensors. Examination of a
trajectory of the vehicle can help make a determination as to
whether it is straddling, changing lanes, and so forth.
[0514] FIG. 91 illustrates another MVIC system 9100, arranged
according to a further embodiment of the present invention, that
contains a driver alert module 9102. Driver alert module 9102 is
used to provide information to occupants of a vehicle, preferably
by means of a visible signal, when the vehicle passes through a
region where tolling transactions are performed. For example, a
vehicle may be assessed a toll by having an RF tag read as it
passes an RF read zone controlled by RF system 6708, or by having a
license plate read as it passes a video capture unit associated
with vision tracking system 6706, if the vehicle is authorized for
pay be plate toll payment. In conjunction with either of the above
operations, module 9102 can alert a driver, for example, that a
toll account associated with the driver's vehicle has an acceptable
balance.
[0515] Recently, new technologies for automatic tolling of vehicles
have emerged, such as pay by plate, where an authorized vehicle can
be assessed a toll by capture of its license plate image, and
"sticker" tag technology, where a toll is assessed by RF
communication between a reader and a small RF tag on a vehicle. In
both technologies, a vehicle passing a tolling region is assessed a
toll without providing information to the vehicle driver as to the
tolling transaction. For example, sticker tags installed on a
vehicle have an embedded RF chip that is able to broadcast a serial
number or other indicator that allows an RF system reading the
sticker tag to deduct money from an account associated with the
sticker tag. Such sticker tags tend to be too small, however, to
provide an alerting signal to the driver when an RF system reads
the tag and charges a toll. In other words, the sticker tag is a
silent tag, by which it is meant that the silent tag is unable to
provide the driver with relevant information concerning the account
that the silent tag is linked to. Similarly, a pay by plate user
after passing through a region where a license plate image is
captured (also termed "read") and a toll assessed to an account
associated with that license plate, is not alerted as to any
information concerning that account.
[0516] Because of the inability of technologies such as sticker
tags and pay by plate to provide direct feedback to a vehicle user
during or after a toll transaction, a vehicle user, such as a
sticker tag user, may in the first instance be assessed a toll
without being aware. In addition, whether aware of tolling
transactions taking place or not, the driver (user) may have no
knowledge of the state of an account balance used to pay the
automatically assessed toll. The balance may be low or insufficient
to pay a toll, in which case the driver may be assessed a violation
without being aware until sometime later. Furthermore, a driver
aware that an account is being depleted during travel through
automatic toll points, may nevertheless have to wait until a phone
call or internet transaction, or other means of account
verification can be performed before determining the state of the
account balance.
[0517] In one embodiment of the present invention, driver alert
module 9102 is triggered to provide a driver with a simplified
account status signal to a driver. Preferably, driver alert module
9102 includes one or more light-emitting devices located in a
roadway that, when activated by a trigger, present a visible sign
to a passing driver. For example, another module (or "system") can
act as a tolling module, where a vehicle toll account is read as
the vehicle is encountered by the tolling module when it passes by.
Referring again to FIG. 68, a tolling module such as system 6708
can perform read or read/write operations with a passing vehicle
having a sticker tag or other silent tag, when the vehicle passes
through one of the read zones of arrangement 6800. When the read or
read/write operation is performed, for example, the account balance
of the vehicle silent tag is read and a toll deducted from the
balance, an alerting signal is triggered. Preferably, a signal is
sent to activate an alerting light visible to the driver. For
example, system 6708 may send a signal that a silent tag account
has been read, and the account balance is satisfactory. This signal
could be sent directly to module 9102 or via central unit 6702 or
via unit 6710. Module 9102 then activates an alerting light to give
an account status signal, for example, alerting the driver of the
silent toll tag vehicle that the account balance associated with
the silent tag is satisfactory.
[0518] In one embodiment of the invention, illustrated in FIG. 92,
the account status signal is a visible light signal arranged within
the roadway and associated with a vehicle travel lane of an RF read
zone used to read the vehicle toll tag. When vehicle 9202 traveling
in lane 9204 passes through RF system 9206, a signal is sent that
activates light source 9208 embedded in the surface of lane 9204.
Lighting source 9208 can be, for example, a high intensity light
emitting diode (LED) whose top surface is located at or near the
surface of lane 9204. Preferably, lighting source 9208 is located
within a central portion of travel lane 9204 so that a driver of a
vehicle traveling within lane 9204 can conveniently see a signal
emitted by source 9208 without having to avert attention from the
roadway in front of the vehicle. Thus, a driver passing through RF
read zone 9210 sees a visible signal in light source 9208 that is
associated with the same lane as that containing RF read zone 9210.
The driver can then recognize the visible signal as indicating the
status of the vehicle toll account.
[0519] In one embodiment, visible light source 9208 can include a
variety of signals (not shown), each representative of a different
account status. For example, in one arrangement, light source 9208
includes individual blue, yellow and green light elements, each
light indicative of a different account status. The blue light, for
example, can indicate insufficient funds to pay for the tolling
transaction just attempted by RF system 9206. Depending on the
exact nature of the toll account, the blue light may additionally
be indicative that a violation is being reported, or it may
indicate to the driver that funds must be replenished within a
certain time in order that a violation not be assessed. Yellow can
indicate that the toll tag account is low, and should be
replenished. Green can indicate that the toll tag contains a
sufficient balance that no action need be taken in the near
future.
[0520] However, other configurations of alerting lights are
possible. In other embodiments of the invention, a single type of
alert signal is sent to a driver after passing through a zone where
an RF toll transaction takes place. For example, a single yellow
light can be activated to alert a driver of insufficient or low
funds in the account associated with the driver's toll tag, or a
single blue light could be used to indicate insufficient funds in
the toll tag account.
[0521] Thus, system 9102 provides a convenient way to alert a
driver as to an account status so that the driver can be apprised
in real time, and be enabled, for example, to take corrective
action when necessary and possibly prevent imminent toll violations
from being enforced, or prevent continued violations from
occurring. Furthermore, a driver receiving a green signal, for
example, is provided with reassurance during a trip, so that time
consuming action need not be taken to check account balances to
ensure that a vehicle can properly be operated on an automatic toll
road.
[0522] In embodiments of the invention, system 9102 employs
specific criteria to set account balance boundaries that delineate
the different account status regions. For example, the green/yellow
account balance boundary might be set based on average vehicle
travel patterns that determine how much more toll charges a driver
is likely to incur within a set period of time.
[0523] In another embodiment of the invention, illustrated in FIG.
93, multiple lighting sources are employed in travel lanes to alert
a passing vehicle as to account status of an RF toll tag account.
As illustrated, a series of three lighting sources 9302 are located
within each lane, where each lighting source may comprise multiple
individual lights, such as blue, green, yellow lights. Lighting
sources 9302 are mutually spaced along lane 9304 so that a driver
in traveling vehicle 9306 can be properly alerted as to RF tag
account balance after the vehicle passes through a tolling point,
such as RF read zone 9308. In one embodiment of the invention, the
individual light source, for example, 9302b, that is activated, is
chosen based on its distance from an RF read zone, for example,
from gantry 9312 associated with read zone 9308, as well as other
factors. For example, a loop sensor system, such as IVIS array 9310
can be used to measure vehicle speed of a passing vehicle, from
which it can be determined the best lighting source 9302 to
activate to catch the driver's attention. Thus, for example, for
faster vehicle speed a signal is sent to activate a lighting source
located at a further distance from the RF read zone. Preferably,
the distance along a roadway in the travel direction between RF
read zone 9306 and alerting signal lights 9302 is about 20 to 120
feet.
[0524] In other embodiments, a visual systems such as VICU 6714, or
vision tracking system 6706 can be used to capture license plate
information and assess a toll for a pay by plate vehicle, as well
as initiate a violation report, if necessary. In these latter
embodiments, lighting sources that are triggered by the visual
system are chosen to be located within a travel lane and spaced
about 20-120 feet (in the direction of vehicle travel) from a
license plate capture camera or other device that acts as a tolling
point.
[0525] In embodiments where only a single lighting source is
employed in a vehicle alert system, the separation distance between
the lighting source and a tolling point can be set based on select
criteria. For example, average vehicle speed and/or average vehicle
spacing in the vicinity of the tolling point can be used to
determine the appropriate separation distance.
[0526] In further embodiments of the invention, the techniques
described above with respect to FIGS. 67-83 and 88-90 that are used
for identifying more accurately vehicle lane position in a
multilane environment, are employed in conjunction with a driver
alert module to provide to a driver passing through a tolling
region a visible alerting signal in the proper travel lane. For
example, combinations of lane straddling diamond sensors, vision
tracking sensors and RF read zones, can be used to accurately
determine lane position of a vehicle whose account is being tolled
and account balance checked. Accordingly, a lighting source in the
vehicle travel lane predicted to be that of the tolled vehicle is
activated.
[0527] In other embodiments of the invention, system 9102 can be
used in conjunction with any combination of other systems (also
termed "modules") such as RF system 6708, IVIS 6704, Vision
tracking system 6706, and VICU 6714, where at least one of the
other modules provides a means for identifying a vehicle or vehicle
toll account and assessing a toll associated with that account.
Accordingly, a driver of an identified vehicle can be alerted that
a toll is being assessed, or simply that information associated
with the vehicle has been recorded. Vehicle identification using
Tandem RF read zones
[0528] FIG. 84 illustrates a tandem RF read zone geometry employed
in conjunction with an IVIS sensor array according to another
exemplary embodiment of the present invention. Tandem RF read zone
system 8400 employs two RF gantries, 8402, 8403 arranged to create
read zones 8404, 8406 that are positioned in tandem for a vehicle
traveling along the direction of traffic flow indicated. The tandem
geometry affords advantages over conventional RF based
technologies, such as automatic vehicle identification (AVI)
systems employed currently in some states for Electronic Toll
Collection (ETC), as discussed in detail below.
[0529] In some AVI systems that employ RF read technology, a
read-only system is employed. This involves simply reading an
identifier from a toll transponder, which can then be used by a
processing unit in an AVI system to charge an account associated
with the identifier, analogous to charging an account associated
with a credit card number. In a transaction carried on with a
passing vehicle, a vehicle tag is read once as it passes through an
RF read zone, and a toll charged to the account associated with the
tag.
[0530] More typically, AVI technology employs read/write
technology, in which information can also be written by an RF
antenna to a toll tag on a passing vehicle. In the latter case, an
RF system first interacts with the toll tag to determine
information such as a transponder number, a transponder ID, a
current balance on the toll tag, and various other data that is
contained on the transponder. Based on this information, the system
makes a decision as to whether a payment valid and write
information back to the transponder. The information typically
includes an updated account balance for the toll tag. Finally, the
system may read the information again to verify that all the
previous transactions took place as planned.
[0531] However, conventional AVI systems conduct the
above-described multiple transactions in a fairly inefficient
manner for vehicles traveling at high roadway speeds. Originally
such systems were designed for stop and go transactions in single
lanes, and not intended to operate in a high speed MVIC
environment. The conventional technology involves reading an RF tag
once while the vehicle is within a single lane, and writing back to
the tag once for read/write systems. However, when a vehicle passes
from one zone of reading and writing in a first lane and into an
adjacent lane, it enters a different zone of reading and writing.
Therefore, a toll transaction started while the vehicle travels
through the first zone may be interrupted before completion. If
another transaction is subsequently started in the second zone
corresponding to the new travel lane, it may also lack sufficient
time to complete before the vehicle leaves the read zone area.
Therefore, revenue is lost and a transaction is not fully
captured.
[0532] In addition, if a read or write process fails, at typical
highway vehicle speeds, there is typically not sufficient time to
conduct a second attempt at reading or writing before a vehicle
leaves a reading zone. Also, the potential exists with conventional
AVI technology for an antenna that is used for a first travel lane
to inadvertently transact with a vehicle transponder in an adjacent
lane or in a straddling region of the lane, and mis-associate the
transponder with a vehicle passing through the first lane
(cross-lane read). This can occur because an RF read signal bounced
off a vehicle transponder in the adjacent lane reflects off the
vehicle in the first lane, causing the transponder of the adjacent
vehicle to be interpreted as residing in the first vehicle.
Therefore, the system could collect revenue from the transponder of
the adjacent lane vehicle while charging the vehicle for violation,
since it was not read by the antenna in its lane. Also, the
potential exists to charge a vehicle transponder in two adjacent
lanes if an RF read zone is sufficiently over-lapping.
[0533] It is common practice in conventional AVI systems to reduce
cross-lane reads using time division multiplexing for adjacent RF
zones, so that antennas are cycled off and on in a pattern that
provides for no adjacent antennas to be on simultaneously. However,
this practice increases the likelihood that a vehicle tag passing
at high speed and changing lanes will fail to be read at all.
[0534] System 8400 of the present invention overcomes the above
problems by providing two large powerful RF read zones 8404, 8406.
As depicted in FIG. 84, RF read zones 8404 and 8406 comprise
respective overlapping subzones 8408 and 8410, each subzone created
by a single antenna of antennas 8412 and 8414, respectively.
Preferably both zones 8404 and 8406 are approximately 20 feet in
length. Preferably the overlap of subzones along a border region
between lanes 8418 and 8420 is such that each antenna 8412 and each
antenna 8414 can read a vehicle that is positioned in either lane.
Preferably, antennas 8412, 8414 are configured so that an antenna
angle can be varied from about 2 degrees to about 35 degrees with
respect to horizontal. In a preferred embodiment, RF zones 8404 and
8406 are kept on continuously. Also included in system 8400 are
IVIS lane straddling sensors 8416a, 8416b, 8416c that can detect
the presence of vehicle lane straddlers.
[0535] In a preferred embodiment, a vehicle toll tag (not shown) is
read while passing through zone 8406. System 8400 is configured so
that a successful read can take place if the vehicle tag passes
through only lane 8418, only lane 8420, or a combination of the two
lanes while traversing zone 8406. For example, continuous reads can
be conducted at a rate of about 300 times per second, or every
three milliseconds, resulting in about 75 reads for a vehicle
traveling at 60 mph through the center of a 20 ft read zone. Thus,
system 8400 has sufficient time to conduct multiple reads of each
passing vehicle, even if a vehicle is straddling the lanes or
passing between lanes, where the amount of successful reads may be
reduced by about 50%.
[0536] In an exemplary embodiment of the present invention, system
8400 is configured to conduct read/write transactions with a
vehicle containing a read/write RF toll tag. FIG. 85 depicts steps
in a method for conducting multiple transactions with a passing
vehicle, according to a preferred embodiment of the present
invention. Referring also to FIG. 84, in step 8502, system 8400
conducts an initial read of a read/write toll tag as a vehicle
enters zone 8406. Preferably, system 8400 collects information such
as tag number and present account balance.
[0537] In step 8504, system 8400 updates the account balance for
the vehicle toll tag. The updated balance reflects a toll deducted
from the present account balance based on a predetermined toll
value to be assessed against the vehicle.
[0538] In step 8506 information is written back to the toll tag
that includes the updated account balance.
[0539] In step 8508, the toll tag is re-read by system 8400 to
determine whether the toll transaction was properly recorded and
the account balance accurately updated.
[0540] In step 8510, system 8400 conducts multiple RF reads of the
vehicle as it moves through secondary RF read zone 8404. In a
preferred embodiment, the multiple reads are conducted primarily to
track the vehicle position as it passes through zone 8402. In this
manner, the vehicle can be properly identified so that system 8400
properly associates the vehicle with the RF transponder
transactions that occurred in steps 8502-8508. This also helps the
system distinguish the paying vehicle from a vehicle passing nearby
that does not have a transponder. Preferably, as the vehicle moves
through zone 8404, lane straddling sensors 8416a-8416c are used to
provide additional vehicle tracking data. In an exemplary
embodiment, a vision tracking system (VTS) described above, is used
to capture vehicle images when the vehicle passes through zone
8404. The lane straddling sensor data, RF data, and VTS data can be
passed to an MVIC controller in order to correctly associate the
paying vehicle and any non paying vehicle with the captured vehicle
images and to classify vehicles, detect vehicle speed, and vehicle
movement. When a vehicle that does not have a valid toll tag
(non-paying vehicle) is identified, further vehicle information of
that vehicle can be gathered and processed, for purposes of general
data collection, statistics, or enforcement. For example, a license
plate image of a vehicle not paying via RF toll tag can be captured
and used to determine whether the non-paying vehicle is a
registered pay by plate vehicle, in which case an appropriate toll
can be assessed by the latter method. If the non-paying vehicle is
not registered to pay by means other than RF toll tag, a violation
report can be forwarded to an appropriate violation enforcement
system.
[0541] In another embodiment of the present invention, system 8400
is employed to conduct transactions with a read only vehicle toll
tag. In this case, the read-only toll tag can be read initially as
the vehicle enters zone 8406 to extract information such as an
account number to charge a toll. The toll tag can be read multiple
times to ensure a correct transaction.
[0542] A benefit of the system of the present invention is that the
tandem RF read zones afford a greater possibility to complete a
series of transactions with a read/write transponder. If, for
example, there is a difficulty in finally writing back to the
transponder and verifying that the correct amounts associated with
a toll transaction are properly received from the transponder,
while the vehicle is in zone 8406, system 8400 can package the
information from the transactions conducted in zone 8406 and send
the information to the transponders of zone 8404 so that any
unfinished transactions can be completed. In other words, the
system continues the transaction series with the vehicle
transponder at a point where it was unable to complete it using RF
read zone 8406. In the example shown in FIG. 84, two tandem RF read
zones create an effective read zone length of about 40 feet for the
case of 20 ft long individual read zones. Thus, system 8400 is
afforded nearly half a second to complete a series of toll
transactions with a vehicle passing at 60 mph.
[0543] Although FIG. 84 depicts an embodiment in which two gantries
8402, 8403 are employed to create tandem RF read zones, other
embodiments can employ a single gantry to create RF tandem read
zones. Moreover, embodiments employing more than two RF antennas in
each gantry for reading more than two lanes are contemplated.
[0544] In another embodiment of the present invention, a dual read
zone system is employed for RF read/write toll tags used in
vehicles traveling in a closed toll road system. In this case, at
the entry point, information on time, date, and vehicle location is
written to the transponder, while at the exit point, this
information is read out to determine the distance traveled on the
toll road, so that a distance-based toll can be assessed.
[0545] In another embodiment of the present invention, RF read
zones 8404 and 8406 are created using mutually different RF
technologies. In this embodiment, read zone 8404 is capable of
communicating with RF devices, such as transponders of a first RF
technology type. Read zone 8406 is capable of communicating with RF
transponders of a second RF technology type. In general, the first
and second RF technology types can differ such that RF tags of
either technology type can only be read or written to by one of
read zones 8404, 8406. For example, the RF read zone technology
associated with read zone 8404 may be unique to a vendor selling a
particular RF toll tag, so that only those vehicles having the
vendor's toll tags can be read in read zone 8404. Similarly, read
zone 8406 may correspond to a second vendor's unique RF technology
also configured to only interact with toll tags sold by the second
vendor. This configuration of a tandem RF read zone system is
useful when vehicles using RF tags of differing technologies are
permitted to concurrently use a common roadway as a tolling road.
Accordingly, in this embodiment, a vehicle having one of two
differing RF toll tags can be read when passing through system
8400, either within read zone 8404 or read zone 8406. The dual
gantry arrangement of FIG. 84 can be extended to include additional
gantries that create additional RF read zones, where the additional
RF read zones employ still other RF technologies for communicating
with still other RF tag types. Thus, in other embodiments, a
multiple RF read zone arrangement for reading one of a multiple set
of different permissible RF tags types is possible.
[0546] In further exemplary embodiments of the present invention,
each RF technology type of a multiple RF read zone system is
associated with a dual RF read zone that operates as described
above to allow reading, writing, and vehicle tracking through
tandem read zones. Thus, in an embodiment used for two different RF
read technologies, four RF read zones are created in tandem, two of
which are used for a first RF technology and the other two used for
a second technology. Accordingly, vehicles having RF toll tags
corresponding to either one of the two RF technologies employed in
the four zone system, can be read, written to, and tracked while
passing through the system.
[0547] Synchronization of Loop Based Sensors
[0548] In a further aspect of the present invention, a system for
controlling loop based sensors in a multilane environment comprises
a master program that controls the sampling periods of loop based
sensors. A common problem that occurs using inductive loop
technology in multiple lanes, either in a multilane open road
environment or a toll plaza or toll ramp environment, is overlap of
adjacent sensor fields during operation. If a first lane and
second, adjacent lane both have loop detectors, where the loop
detectors of the first and second lane are located next to each
other, the probability exists that at various times the loop
detectors will be on at the same time and overlap frequencies. When
the adjacent loops are on simultaneously, a mutual change of
induction within each loop is likely to be induced, such that one
or both of the loops may be interpret the change to indicate a
vehicle presence, even in the absence of a vehicle. In addition, if
a vehicle is present, the change in inductance induced by mutual
overlap could confuse an inductive loop that the vehicle passes
over into miscounting the number of vehicle axles and
misclassifying the vehicle.
[0549] In a preferred embodiment of the present invention,
individual loop detector controllers are configured to control
sampling periods of loop sensors (or sensors) within individual
lanes such that the sampling periods of loop sensors within one
lane are coordinated with the sampling periods of loop sensors
within adjacent lanes. Preferably, like sensors in a sensor array
in a first lane are placed adjacent to like sensors of sensors in
adjacent lanes, as illustrated in FIG. 86. Each lane of lanes 8610,
8612, and 8614 contain a group of loop sensors 8602, 8604, 8606,
8608. In this embodiment, each sensor of each group of four sensors
is arranged adjacent to a like sensor (same sensor type) in one or
more adjacent lanes. In other embodiments, each sensor group in an
individual lane comprises eight individual sensors. In still other
embodiments, sensors are arranged next to different sensor type in
an adjacent lane.
[0550] Referring to FIG. 86, a master program communicates with
loop detector controllers for each lane 8610, 8612, and 8614. The
master program sends instructions that determine sampling periods
for the loop sensors depicted in FIG. 86. The sampling periods are
arranged so that any loop sensor is not being sampled during a
sampling period of a loop sensor immediately adjacent in an
adjacent lane. For example, if sensor 8604 in lane 8612 is on, then
sensors 8604 in lanes 8610 and 8614 are off for the duration of
sampling of 8604 in lane 8612.
[0551] FIG. 87 shows a control page 8700 of a master program for
controlling sampling periods in an exemplary multilane loop sensor
system configured as an IVIS system that contains eight lanes with
IVIS sensors, according to an embodiment of the present invention.
Two of the lanes contain four IVIS sensors and the remaining lanes
each contain eight sensors. As illustrated, each sensor position
status is shown for a given moment in time. An overall checkerboard
pattern is formed where every "primary sampling period" sensor
(indicated by a "1") is surrounded by "secondary sampling period"
(indicated by "0") sensors, both in adjacent lanes, and at adjacent
positions within a lane of the "primary sampling period" sensor.
The master program controls the IVIS sensor sampling pattern shown
in FIG. 87 such that any position in the checkerboard oscillates
from primary sampling period to secondary sampling period according
to a period corresponding to the sensor sampling period.
[0552] In order to synchronize an entire toll plaza regardless of
its quantity of IVIS sensors, so that a checkerboard pattern of
sensor sampling is maintained, a synchronization signal is sent to
all IVIS detectors. Preferably, the master program communicates
with IVIS detectors over an Ethernet, serial or a dedicated
communications line. Preferably, a signal is sent at one time to
all IVIS detectors with instructions to begin a primary sample
period instantly or at a predetermined time. In an exemplary
embodiment, this synchronization signal is sent to every sensor on
a predetermined time schedule. For example, a synchronization
signal could be sent every 10 to 15 seconds or every 30 seconds,
depending on an amount of drift in crystals used for clock timing
within the detectors.
[0553] In another embodiment, if clock speed of detectors used in
an IVIS system are extremely accurate and have no drift, only a
single synchronization signal is sent. Thus, a single
synchronization upon start up of all lanes is sent.
[0554] In still another embodiment of the invention, all detector
boards corresponding to the IVIS detectors are synchronized
according to the phase of a common power source used to power all
the IVIS detectors.
[0555] The foregoing disclosure of preferred embodiments of the
present invention has been presented for purposes of illustration
and description. It is not intended to be exhaustive or to limit
the invention to the precise forms disclosed. Many variations and
modifications of the embodiments described herein will be apparent
to one of ordinary skill in the art in light of the above
disclosure. For example, with respect to the structure or operation
of an MVIC system, use of any combination of the systems 6704,
6706, 6708, 6710, and 6714 is believed within the scope of the
invention. Furthermore, use of the aforementioned systems, in
particular systems 6704, 6706, 6708, and 6714 to collect and manage
vehicle information other than for tolling purposes is within the
scope of this invention. For example, image capture, vision
tracking, and vehicle classification performed by the
aforementioned systems can be used for the purposes of data
collection or law enforcement purposes. The scope of the invention
is to be defined only by the claims appended hereto, and by their
equivalents.
[0556] Further, in describing representative embodiments of the
present invention, the specification may have presented the method
and/or process of the present invention as a particular sequence of
steps. However, to the extent that the method or process does not
rely on the particular order of steps set forth herein, the method
or process should not be limited to the particular sequence of
steps described. As one of ordinary skill in the art would
appreciate, other sequences of steps may be possible. Therefore,
the particular order of the steps set forth in the specification
should not be construed as limitations on the claims. In addition,
the claims directed to the method and/or process of the present
invention should not be limited to the performance of their steps
in the order written, and one skilled in the art can readily
appreciate that the sequences may be varied and still remain within
the spirit and scope of the present invention.
* * * * *