U.S. patent number 3,663,937 [Application Number 05/044,491] was granted by the patent office on 1972-05-16 for intersection ingress-egress automatic electronic traffic monitoring equipment.
This patent grant is currently assigned to Thiokol Chemical Corporation. Invention is credited to Thomas E. Bolner.
United States Patent |
3,663,937 |
Bolner |
May 16, 1972 |
INTERSECTION INGRESS-EGRESS AUTOMATIC ELECTRONIC TRAFFIC MONITORING
EQUIPMENT
Abstract
An electronic detection circuit identifies several traffic paths
through an intersection as a vehicle passes over a predetermined
sequence of discrete separated positions identifying a path. A
television camera can view the intersection and the paths be
identified on a receiving cathode ray tube screen by placing a
series of light detectors over desired patterns. A switching
circuit responsive to the detectors then identifies and counts only
those vehicles passing one complete sequence of the positions
identifying a particular path.
Inventors: |
Bolner; Thomas E.
(Fayetteville, TN) |
Assignee: |
Thiokol Chemical Corporation
(Bristol, PA)
|
Family
ID: |
21932670 |
Appl.
No.: |
05/044,491 |
Filed: |
June 8, 1970 |
Current U.S.
Class: |
340/937;
348/149 |
Current CPC
Class: |
G08G
1/04 (20130101); G08G 1/0133 (20130101); G08G
1/0116 (20130101) |
Current International
Class: |
G08G
1/04 (20060101); G08g 001/04 () |
Field of
Search: |
;340/38R,38L,38P,22,23,24,39,38S ;178/DIG.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Claffy; Kathleen H.
Assistant Examiner: Myers; Randall P.
Claims
What is claimed is:
1. An electronic system for determining traffic patterns comprising
in combination, a series of electronic position detectors arranged
in the form of at least one predetermined traffic path on an
electronic image receiving screen and so spaced as to detect the
position of a vehicle at predetermined sequential positions in a
pattern in said path, an electrical switching circuit with a
plurality of switching stages connected to operate in sequence to
actuate a final switch stage only in response to said detectors
when said vehicle travels through said traffic path in said pattern
in the predetermined sequence of positions, and an egress
counter-circuit connected for counting the number of switching
operations, at said final switch stage.
2. The system defined in claim 1 including an ingress counter
coupled for response to an initial one of the switching stages.
3. The system defined in claim 1 wherein the traffic path is of an
intersection to identify a vehicle making a turn.
4. A system as defined in claim 1 wherein the electronic position
detectors comprise a series of light detectors placed on a
television screen displaying traffic moving through said
pattern.
5. A system as defined in claim 1 wherein each switching stage in
said sequence comprises a prior relay with a contact connected for
enabling the next sequential switching stage only when a vehicle
passes through said sequence of positions to energize said prior
relay.
6. An electronic traffic pattern determining system for analyzing a
plurality of traffic patterns at an intersection comprising in
combination, a television camera directed to view traffic at said
intersection, a television receiver with a cathode ray tube screen
displaying a view of the traffic at said intersection in response
to the camera signals, a set of light discriminating devices
located at discrete separated sequential positions in a
multiplicity of traffic patterns on said screen to detect at least
two discrete paths a vehicle may take through said intersection, a
switching circuit responsive to said devices to identify traffic
patterns of a vehicle encompassing a full sequence of said devices
responding to a particular one of said vehicle paths, and a
counting circuit actuated by said switching circuit only when a
vehicle passes each sequential position identifying said particular
one path.
7. A system as defined in claim 6 wherein said light discriminating
devices comprise means for temporarily locating and holding them on
said screen but permitting them to be moved to other positions when
desired.
8. An electronic traffic pattern determining system for displaying
a plurality of traffic patterns at an intersection comprising in
combination means for producing an image of said intersection and
means for displaying said image, electronic vehicle path detection
means on said image displaying means identifying a set of discrete
sequential detector positions in at least two paths vehicles may
take through said intersection, means converting each of said
detector positions into an electrical signal, a switching circuit
responsive to only a sequence of said electrical signals
identifying a vehicle path through each possible discrete position
in one of said paths, and egress counting means connected for
totalling each response of said switching circuit.
Description
The present invention relates generally to traffic monitoring
systems and more particularly it relates to an electronic system
for tracing vehicles through a plurality of optional paths at an
intersection.
Traffic control has increased in complexity to the extent that most
cities, with a population of 30,000 or greater, engage the services
of a Traffic Engineer to establish and maintain a program for
controlling vehicular movement on the city's streets. In pursuit of
these objectives, the Traffic Engineer makes use of "traffic
surveys" which, among other things, tell him what the traffic
density and turning movements are at various intersections. He is
interested in the number of vehicles which pass through an
intersection; their direction of ingress and egress; and, variation
in traffic flow patterns during the day.
Manual counting is the current technique for establishing these
traffic flow patterns at intersections. One man can count the 12
basic movements of a single intersection at off hours (a vehicle
can enter from one of four directions and execute one of three
movements on egress). More complex intersections, or high density
traffic at peak hours, can require as many as four or more men to
count the vehicles and record their movement through the
intersection. Normally, a survey is conducted for 12 continuous
hours, and this requires relief personnel. The man-hour costs for
these surveys is a basic problem confronting all Traffic
Engineers.
Current state-of-the-art traffic systems record only the number of
vehicles or axles passing through a sensing zone or over a
pneumatic tube. These devices can be used to indicate the number of
ingress and egress vehicles at an intersection, but they can not
record turning movements in the intersection. In order to record
turning movements the system must be capable of sensing the
ingressing vehicle, trace it through the intersection, and record
its egress direction.
Accordingly, it is a main object of this invention to provide an
improved traffic monitoring system which can trace the path of a
vehicle through an intersection.
Another object of this invention is to provide traffic monitoring
equipment which is capable of tracing a multiplicity of vehicle
paths through a complex intersection.
A still further object of the invention is to provide versatile and
efficient equipment that will provide automatic traffic counts and
be capable of simple adaption to different traffic patterns and
different intersections.
Other objects, features and advantages of the invention will be
found throughout the following description and accompanying
drawings illustrating the embodiment wherein:
FIG. 1 is a sketch illustrating vehicle traffic at a typical
intersection;
FIG. 2 is a block diagram of an electronic television automatic
traffic monitoring system afforded by the invention;
FIG. 3 is a side view partially in section of a rubber cup assembly
that may hold a light detecting device on the screen of a
television tube in accordance with the teachings of this invention;
and
FIG. 4 is a schematic switching circuit diagram, of a portion of
the switching system of FIG. 2, partly in block, for identifying a
particular sequence of vehicle positions in a predetermined traffic
path.
FIG. 1 indicates the movements which vehicle "A" can make at a
simple intersection. A zone counter at each point of egress for
vehicle "A" (N, E, or S exit lane) could discriminate the movement
of vehicle "A" if this were the only vehicle entering the
intersection. Also, these zone counters could discriminate the
total vehicular movement of the east bound ingress lane if this
were the only ingressing lane for the intersection. However, if
vehicles "A", "B", "C" and "D" each executed a right turn through
the intersection, zone egress counters at each point of exit could
not discriminate this movement from a left turn or a straight
through movement for each vehicle.
In order to discriminate the movement of each vehicle, that vehicle
must be "tracked" through the intersection and counted upon egress.
(This assumes there is no lane control, such as a left turn lane,
where all vehicles entering the lane must execute a specific
movement). Tracking and counting the vehicle through the
intersection will be accomplished with an "Ingress-Egress
Sequential Counter Circuit" as later described in connection with
FIG. 4 functioning on radiant energy from the face of a cathode ray
tube in a television receiver as shown in FIG. 2.
The television camera and receiver are state-of-the-art systems
which will function under natural lighting conditions or where the
field of view is lighted with infra-red or other mono-wave band
light.
The sequential counter circuit of FIG. 4 is composed of solid state
switches 12 which are secured to the face of the cathode ray tube
11 in FIG. 2 and activated by light energy emitted from the tube.
These solid state switches can be individually secured to the face
of the tube with vacuum cups 13 as shown in FIG. 3 or preassembled
in the form of flexible strips which can be secured to the face of
the tube. This structure permits the system to be readily adapted
to identify different types of paths and different types of
intersections or traffic patterns without any change in the system;
since each switch 12 can be temporarily held in a location
identifying a position in one traffic path until the system is
moved to another intersection or the path through the intersection
is changed, whereupon the switch 12 can be moved to another
position on the screen 14 of cathode ray tube 11.
Each switch 12 may be simply a standard photo-resistive device that
is responsive to a change from a normal null-setting that
identifies a cleared intersection picture on the screen 14 to
change its resistance when the image of a vehicle enters that
position and changes the light level.
FIG. 1 illustrates the positioning of detectors at sequential
discrete positions for two ingressing lanes at the typical
intersection shown. (The north and east ingressing lane detectors
are not shown for purposes of clarity). Assume Vehicle A is in the
process of turning left and Vehicle B is in the process of passing
north. Counters are diagrammatically shown by notation C-W.sub.i
which indicates the west ingress and C-WS.sub.E which shows the
west to south egress path of the vehicle, etc. Thus if Vehicle A is
considered, the ingress from west into the intersection will be
recorded on Counter C-W.sub.i when detector 1 is encountered. As
the vehicle passes into position A' it will sequentially pass
detectors 1 through 5, and when it completes the turn it will
sequentially pass detectors 1 through 10.
If Vehicle A is waiting at position A' for Vehicle B to pass
through position B', it may be seen that detector position 6 is not
yet encountered by any car even though Vehicle B encounters and
passes detector positions 7 through 10 in sequence while Vehicle A
is waiting at position 5. Thus the detector positions are placed
logically in a pattern to identify uniquely by their sequence the
different paths under observation. In this respect a special
switching system for identifying sequential positions (15, FIG. 2)
is provided for each traffic path to be observed. Each path may
have a switching circuit of the nature shown in FIG. 4.
In the sequential switching circuit embodiment illustrated it may
be seen from FIG. 1 that positioning the detectors so that at least
two are encompassed at one time by the vehicle will prevent any
problems of timing in releasing an energization contact 21 etc.,
before the next sequential position is entered.
Improper traffic movement such as one vehicle passing another in
the intersection will result in that vehicle not being counted.
Also, an improper turning movement, such as vehicle "A" turning
left into the north ingress lane, will result in his egress not
being counted.
As seen in FIG. 4, blocks 1-9 represent the sequentially numbered
position detectors of FIG. 1, which may be for example the light
detectors 12 positioned on the television screen 14 of FIG. 2. As
the initial detector 1 is energized then the battery 18 may be
connected to both ingress counter 17 for one count and to relay 19
serving to close contact 20 and connect detector 2 to the battery
18. Thus detector 2 can only be energized in sequence after
detector 1 shows entry of a vehicle. The same action progresses
until, as the vehicle enters the position of the tenth detector 10
in sequence, then the egress counter 16 is counted once,
identifying the number of vehicles taking the designated path of
detector positions 1 through 10 in sequence.
As may be seen from FIG. 1, if position 6 is missed, then detector
7 will not be connected to battery 18 and Vehicle B passing
position B' will not serve to operate egress counter 16 (C - W
N.sub.E). It is clear that other equivalent switching circuits can
be used to perform the necessary function of identifying the
sequence of adjacent positions.
As seen in FIG. 2, a technician may mount the camera 21 above the
intersection to view a field 22 including the portion of the
intersection identified in FIG. 1. The camera could be mounted on a
boom, telephone pole, at an upper story window overlooking the
intersection, or any convenient overhead structure. After the
camera and, if required, special light source is mounted the
sequential counting circuits would be attached where required to
the screen 14 of the tube 11 operated by television receiver 23 by
means of appropriate wires 24 or radio link. The technician would
then connect the counting circuits to their appropriate counters
and visually check the output of the counters against the observed
traffic pattern.
Hourly counts or any predetermined periodic counts could be
recorded electrically or photographically. Also, if it were
desirable to count more than one intersection at any given time, a
televised tape could be made of each intersection and this could be
played back (at high speed) to the counter.
Of particular importance in the television system embodiment shown
is the ability to remove detector positions 12 easily and replace
in different paths or patterns, and to conform to differently
shaped intersections or traffic paths if desired.
It is to be understood that the form of the invention herewith
shown and described is to be taken as a preferred example of the
same and that various changes may be resorted to without departure
from the spirit of the invention or the scope of the subjoined
claims.
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