U.S. patent application number 11/342064 was filed with the patent office on 2007-03-15 for internet based highway traffic advisory system.
This patent application is currently assigned to ASTI Transportation Systems, Inc.. Invention is credited to Peter Mr. Krikelis.
Application Number | 20070061065 11/342064 |
Document ID | / |
Family ID | 36697989 |
Filed Date | 2007-03-15 |
United States Patent
Application |
20070061065 |
Kind Code |
A2 |
Mr. Krikelis; Peter |
March 15, 2007 |
Internet based highway traffic advisory system
Abstract
A real time traffic control system that includes a plurality of
roadside sensors and variable message displays arrayed along the
highway connected to the Internet, and communicating with a central
computer using the Internet. Each roadside device includes a modem
and has a unique internet address. The central computer is
programmed to create on demand a plurality of individual virtual
communication ports, each of the ports corresponding to each of the
unique device addresses, whereby said computer communicates in a
quasi-simultaneous manner with all of the roadside devices.
Inventors: |
Mr. Krikelis; Peter;
(Wilmington, DE) |
Correspondence
Address: |
RATNERPRESTIA
P.O. BOX 1596
WILMINGTON
DE
19899
US
|
Assignee: |
ASTI Transportation Systems,
Inc.
18 Blevins Drive
Wilmington
DE
19720
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20060167617 A1 |
July 27, 2006 |
|
|
Family ID: |
36697989 |
Appl. No.: |
11/342064 |
Filed: |
January 26, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60/647,511 |
Jan 27, 2005 |
|
|
|
Current U.S.
Class: |
701/117 ;
455/414.1 |
Current CPC
Class: |
G08G 1/096741 20130101;
G08G 1/096775 20130101; G08G 1/096716 20130101 |
Class at
Publication: |
701/117 ;
455/414.1 |
International
Class: |
G08G 1/00 20060101
G08G001/00 |
Claims
1. A method for obtaining real time traffic related information on
a highway location using a plurality of roadside devices said
roadside devices comprising traffic sensors, the method comprising:
i. providing a plurality of roadside devices comprising at least
one traffic sensor along said highway for detecting traffic flow
past said highway location and connecting said roadside devices to
the Internet; ii. providing a central control computer also
connected to the Internet via a modem, wherein said central control
computer is programmed to provide a plurality of active virtual
ports connected to the Internet through said modem, iii. obtaining
a device Internet address for said central control computer and for
each of said plurality of roadside devices and assigning a virtual
port in said central control computer to each of said devices
address; iv. establishing an Internet connection between each of
said at least one roadside device and said central control computer
whereby said central control computer accesses said each of said
roadside devices through said assigned virtual port.
2. The method according to claim 1 wherein the step of connecting
said plurality of roadside devices to the Internet is performed
using digital cellular modems.
3. The method according to claim 1 wherein said plurality of
roadside devices further comprises means to communicate a message
to a passing motorist.
4. The method according to claim 3 wherein said message
communicating means comprises a variable message board (VMS) also
connected to the Internet.
5. The method according to claim 4 wherein said Internet connection
is performed using a digital cellular modem.
6. The method according to claim 1 wherein said plurality of
roadside devices comprises a plurality of roadside traffic sensors
and at least one variable message board, each of said roadside
traffic sensors having a unique Internet address and each of said
at least one variable message board also having a unique Internet
address and wherein the central control computer communicates with
each of said roadside devices using a plurality of software
generated unique virtual port, and wherein said communication
occurs quasi-simultaneously.
7. The method according to claim 6 wherein said central computer is
connected to the Internet using an Ethernet port.
8. The method according to claim 6 wherein said Internet address is
an IP address.
9. The method according to claim 6 wherein said Internet address is
a URL address.
10. A real time traffic control system comprising: a plurality of
roadside sensors arrayed along the highway and connected to the
Internet and each having a unique Internet address; a central
control computer also having a unique Internet address and
connected to the Internet, said control computer programmed to
create on demand a plurality of individual virtual communication
ports, each of said virtual communication ports corresponding to
each of said unique device addresses, whereby said computer
communicates in a quasi-simultaneous manner with said plurality of
roadside devices.
11. The control system according to claim 10 further comprising at
least one information communicating means also having a unique
address and also connected to the Internet.
12. The system according to claim 11 wherein said roadside sensors
and said information communication means are connected to the
Internet through a digital cellular modem.
13. A method for communicating with a plurality of roadside display
devices positioned along a highway, the method comprising: i.
providing a plurality of roadside display devices along the highway
for displaying messages to passing motorists and connecting the
plurality of roadside display devices to the Internet; ii.
providing a central control computer also connected to the
Internet, wherein the central control computer is programmed to
provide a plurality of active virtual ports connected to the
Internet, iii. obtaining a device Internet address for each of the
plurality of roadside display devices and assigning at least one of
the plurality of active virtual ports in the central control
computer to the device Internet address of each roadside display
device; iv. establishing an Internet connection between each of the
plurality of roadside display devices and the central control
computer whereby the central control computer accesses each of the
roadside display devices through the assigned virtual port.
14. The method according to claim 13, wherein the step of
connecting the plurality of roadside display devices to the
Internet is performed using digital cellular modems.
15. The method according to claim 13, wherein each of the roadside
display devices have a unique Internet address and wherein the
central control computer communicates with each of the roadside
display devices using a plurality of software generated unique
virtual ports, and wherein the communication occurs
quasi-simultaneously.
16. The method according to claim 15, wherein the Internet address
is an Internet protocol (IP) address or a uniform resource locator
(URL) address.
17. The method according to claim 13, further comprising: polling
the roadside display devices in a quasi-simultaneous manner in
order to verify information displayed by the plurality of roadside
display devices.
18. A real time roadside display device verification system
comprising: a plurality of roadside display devices arrayed along a
highway and connected to the Internet, each roadside display device
having a unique device address; a central control computer also
having a unique Internet address and connected to the Internet, the
control computer programmed to create on demand a plurality of
individual virtual communication ports, each of the virtual
communication ports corresponding to each of the unique device
addresses, whereby the computer communicates in a
quasi-simultaneous manner with the plurality of roadside display
devices.
19. The system according to claim 18, wherein the roadside display
devices are connected to the Internet through a digital cellular
modem.
20. The system according to claim 18, wherein the central control
computer is configured to poll the roadside display devices in a
quasi-simultaneous manner in order to verify information displayed
by the plurality of roadside display devices.
Description
CROSS REFERENCE TO RELATED APPLICATIONS.
[0001] This application claims the benefit of priority to U.S.
Provisional Application No. 60/647,511 filed on Jan. 27, 2005, the
contents of which are incorporated herein by reference in their
entirety.
FIELD OF THE INVENTION
[0002] This invention relates to a centrally controlled highway
traffic advisory system and associated method and more particularly
to a system and associated method for simultaneously addressing a
plurality of remote sensors and displays from a remote location via
the Internet.
BACKGROUND OF THE INVENTION
[0003] Highway construction zones and accidents are often a major
source of congestion in highways as they interrupt the normal
traffic flow due to temporarily restricting the available highway
lanes. Reduction of the number of available traffic lanes and
re-routing the traffic to improvised new traffic lanes cause
conditions that are unexpected by the motorist.
[0004] To alleviate such congestion systems have been developed
that advise the motorist well ahead of the construction or other
incident zones of traffic problems ahead, and anticipated
congestion and reduced speed requirements. Such systems may be
either temporary, using free standing signaling devices such as
remotely controllable traffic lights or variable message boards
(VMS) in communication with a remote central controller together
with movable roadside traffic flow sensors, or fixed using
permanently installed variable message boards in combination with a
remote controller and either permanent or temporary roadside
traffic sensors. Roadside traffic flow sensors have been known to
include occupancy detectors which detect vehicle flow interruption
in a highway lane, traditional speed detectors and video
cameras.
[0005] Typically such systems include a central control, usually
located in the vicinity of the incident or construction zone but
also possibly remote thereof. The central control is almost always
a computer adapted to receive status information from different
roadside devices and able to remotely control such devices so as
to, in the case of a VMS for example, display messages to the
motorists well ahead of the problem zone.
[0006] Communications between the central control and the roadside
devices may be by hard wire connection, telephone link, or radio
frequency transmitter/receiver (Transceiver). In such case, the
roadside device and the central control include modems for
communicating with each other. "Advanced Portable Traffic
Management System Work Zone Operational Test" by Nookala et al
describes a highway safety system that incorporates the use of
widespread spectrum radio, cellular phone and Integrated Services
Digital Network (ISDN) phone links. The spread spectrum radio is
used to link roadside nodes to the central control computer. The
signal transfers from node to node, the nodes acting both as relay
and a means of communication between nodes. Together with the ISDN
link and cellular phone the system performs as part of an Ethernet
network. Each remote terminal (roadside) is equipped with an
Ethernet EHUB which allows multiple devices to share the Ethernet.
The system includes establishment of a web page to provide traffic
information accessible by motorists planning a trip through the
Internet.
[0007] Thus there presently are known a number of sophisticated
systems used in traffic control. However what these systems have in
common is the sequential polling of the different roadside devices
regardless of the communication mode adopted in the system. A much
more efficient mode of communication would be the
quasi-simultaneous polling of all devices particularly if such
polling could be implemented in a continuous mode.
SUMMARY OF THE INVENTION
[0008] There is, therefore, provided in accordance with the present
invention a method for obtaining real time traffic related
information on a highway location by:
[0009] i. Providing a plurality of roadside devices comprising at
least one traffic sensor along the highway for detecting traffic
flow past a desired highway location and connecting the roadside
devices to the Internet using a modem.
[0010] ii. Providing a central control computer also connected to
the Internet via a modem, wherein the central control computer is
programmed to provide a plurality of active virtual ports connected
to the Internet through the modem.
[0011] iii. Obtaining a device Internet address for the central
control computer and for each of the plurality of roadside devices
and assigning a virtual port in the central control computer to
each of the devices address.
[0012] iv. Establishing an Internet connection between each of the
roadside devices and the central control computer whereby the
central control computer accesses each of said roadside devices
through the assigned virtual port.
[0013] The connection of the roadside devices to the Internet is
preferably done using digital cellular modems, and, in at least one
embodiment of this invention, variable message boards along the
highway are used to communicate messages to passing motorists. The
variable message boards are also connected to the central control
computer using an Internet connection.
[0014] Still in accordance with the present invention, the
plurality of roadside devices comprises a plurality of roadside
traffic detectors and at least one variable message board, each of
said roadside traffic sensors having a unique Internet address and
each of said at least one variable message board also having a
unique Internet address; the central control computer communicates
with each of said roadside devices using a plurality of software
generated unique virtual ports.
[0015] There is further contemplated according to this invention, a
real time traffic control system comprising a plurality of roadside
sensors arrayed along the highway each having a unique Internet
address and each connected to the Internet. The system further
comprises a central control computer also having a unique Internet
address and connected to the Internet. The control computer is
programmed to create on demand a plurality of individual virtual
communication ports, each corresponding to one of the unique device
addresses, whereby the computer communicates in a
quasi-simultaneous manner with the roadside devices. Digital
cellular modems are used to connect the roadside devices to the
Internet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic figure representing a system according
to this invention implemented along a highway.
[0017] FIG. 2 is a flow diagram of exemplary steps for poling
sensors and updating message boards in accordance to various
aspects of the present invention.
[0018] FIG. 3 is a schematic diagram showing the establishment of
communication with sensors and the outflow of information in
accordance with an aspect of the present invention.
[0019] FIG. 4 is a schematic diagram showing the inflow and
handling of information from sensors received in the central
computer in accordance with aspects of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The invention will next be described with reference to the
figures wherein same numerals are used to identify same elements in
all figures. The figures illustrate the invention and are not
intended to act as engineering or construction drawings, therefore
they are not to scale and do not include all elements that may be
included in such drawings, as inclusion of such elements would
unduly clutter the drawings.
[0021] Referring next to FIG. 1 there is shown a highway 10 on
which there have been deployed a plurality of means 12 to
communicate a message to passing motorists. Such means typically
comprise roadside display devices such as variable message boards,
which, by way of illustration rather than limitation, may be either
portable devices of the type disclosed in U.S. Pat. No. 5,231,393
issued to Strickland et al. in 1993 or fixed, or combinations of
the two. Such roadside display devices typically provide for a
plurality of messages to be displayed to passing motorists, and the
message displayed may be pre-programmed actuated upon receipt of a
pre-arranged code signal or composed and transmitted to the device
from a remote location. However the message communication means may
also comprise traffic signals (including traffic metering devices
and conventional traffic lights), highway advisory radio or any
other means that will notify a motorist of potential traffic issues
ahead. We will refer to all such display devices from hereon as
VMS.
[0022] Also deployed along the highway there is shown a plurality
of roadside traffic detection sensors 14. Roadside sensors 14, by
way of illustration rather than limitation may be speed sensors,
occupancy sensors, sensors that determine the type of traffic
passing through a designated zone, i.e. long (trucks) or short
(passenger) vehicles, video cameras and/or combinations thereof.
The roadside sensors may operate using infrared radiation, radar or
any other convenient detection system.
[0023] Collectively we will refer to roadside displays/VMS and
sensors as roadside devices.
[0024] Associated with each of the roadside devices, is a modem 16
such as a broadband data modem. Modem 16 may be a Code Division
Multiple Access (CDMA), a Global System for Mobile computing (GSM)
or an equivalent thereof. Each of the modems 16 provides a
connection, preferably a high speed connection, between the
roadside device and a global information network (e.g., the
Internet) through a digital cellular data phone line, e.g., via the
nearest cellular phone tower 24. As used herein, the term
"Internet" refers to all such networks including, by way of
illustration rather than limitation, the Internet, Internet2, and
other such networks. Each of the roadside devices has an individual
Internet address (herein "address"), preferably an Internet
protocol (IP) address, that identifies the location of the device
over the Internet.
[0025] A centrally located controller 18, i.e. a computer, usually
located in a secure and convenient place unrelated to the zone or
zones where the roadside devices are deployed, is also connected to
the Internet. Such connection is most likely but not exclusively, a
hard wired connection to a high speed Internet access provider.
Obviously the controller can be located anywhere where Internet
access is possible which in practical terms means almost anywhere
in the world.
[0026] The central control computer is programmed to poll the
roadside devices and obtain therefrom traffic information or send
thereto instructions. For example the central control device may
poll the traffic sensors and obtain data relating to real time
local traffic flow. The central control computer may then send to
the VMS's a command to display a message advising motorists of
traffic conditions ahead.
[0027] The central control computer may be further programmed to
provide certain commands and display messages automatically to the
VMS's, such messages depending on the traffic information obtained
from the traffic sensors, or the central control may display the
information to an operator and the operator may in turn select the
appropriate message to be communicated to the motorists on the
highway. It is still within the scope of the present invention to
provide a remote control computer connected to the central control
computer and able to communicate with the central control computer
via the Internet thereby to provide access to the central control
computer from a remote location.
[0028] Alternatively, the central control computer does not have to
be in a fixed location, but can be any properly programmed computer
in a location with access to the Internet.
[0029] FIG. 2 depicts a flow chart 200 of exemplary steps for
polling sensors and displaying messages on VMS's in accordance with
one embodiment of the present invention. At block 202, a
polling/message display application (herein the "application") is
initiated, virtual ports are reserved, and timers are starter. In
an exemplary embodiment, the application resides on the central
control computer and may be initiated by a user in a conventional
manner. Upon initiation, the application reserves virtual ports
within the central control computer and starts timers that control
polling of the sensors and display of messages on the VMS's. A
virtual port may be reserved for each unique one of the sensors and
the VMS's for communications between the central computer and the
sensors and VMS's. For example, if there are four (4) sensors and
three (3) VMS's, the application may reserve seven (7) virtual
ports for communication with these devices. In an exemplary
embodiment, an identifier for each device and an associated virtual
port are stored in a table. In addition, the address for each
device may be stored in the table.
[0030] At block 204, the application sets a sensor device flag and
indicates the number of sensors (Q) to be polled by the central
control computer. The application then enters a loop, blocks
206-214, for sequentially establishing communication with the
individual sensors. A counter 205 increments a sensor value N after
each pass through the loop. The loop starts with establishing
communication with a first sensor (N=1) and ends after establishing
communication with a last sensor (N=Q).
[0031] The following is sample coding loop from the application for
polling roadside sensors such as for example a queue detector:
TABLE-US-00001 For intLoopCounter = 1 to TOTALQ MDIForm
1.udpPeerQ(intLoopCounter).SendData(strToSend) MDIForm
1.StatusBar1.Panels(1) = "Sending-> "
&.Fields("RadioAddress") & Chr(&HFF) &
Chr(&H8F) & Chr(&H1) & Chr(&H2) &
Chr(&H2) MDIForm 1. StatusBar1.Panels(2) ="" Next
intLoopCounter.
[0032] At block 206, a virtual port number and an address for the
sensor are obtained. The virtual port number and the address for
the current sensor may be obtained from the table discussed above
with reference to block 202.
[0033] At block 208, a control for the sensor is created at the
central control computer. Parameters such as port number, address,
and polling string are passed to the control for defining
communications between the central control computer and the sensor.
In an exemplary embodiment, the control is a Windows Socket
(Winsock) control. The Winsock control may be created through a
subroutine that is called with the statement "MDIForm 1.udpPeerQ
(intLoopCounter) .SendData(strToSend)" in the above sample coding
loop.
[0034] At block 210, the central control computer establishes a
connection with the sensor and sends polling data to the sensor
through the established connection. In an exemplary embodiment, the
connection is in accordance with a User Datagram Protocol (UDP). In
accordance with this embodiment, the polling data may be sent by a
SendData method associated with a SocketWrapper object that pushes
a datagram which traverses the Internet as one packet that takes
one path to the sensor or as multiple packets that follow multiple
paths to the sensor. In alternative exemplary embodiments, the
connections may be in accordance with TCP/IP or other such
communication protocol. As a practical matter, the central control
computer may be connected to the Internet and communications from
the central control computer may travel from the central computer
over the Internet to a transmitter (cellular tower) where it is
transmitted to a modem associated with the device to which
communications are being sent.
[0035] At block 212, a data receiving period begins for receiving
responses to the polling data from the sensor, e.g., through the
Winsock control for that sensor.
[0036] At block 214, the application checks if the sensor is the
last sensor (e.g., N=Q). If the sensor is the last sensor (e.g.,
N=Q), processing proceeds at block 216. Otherwise, if the sensor is
not the last sensor (e.g., N<Q), processing proceeds at block
204 with the steps of blocks 204-214 repeated for the next
sensor.
[0037] At block 216, the receiving period for the sensors, which
began at block 212, ends. In an exemplary embodiment, data from a
sensor may be received at essentially anytime after poll data is
sent to that sensor and ends sometime after the last sensor is
polled. Thus, there is an overlap period during the receiving
period in which data from multiple sensors may be received by the
central control device. After the receiving period ends, the
control created at block 208 may be terminated.
[0038] In the exemplary embodiment, the virtual ports established
within the central control computer enable the central control
computer to receive packet of data from multiple sensors in any
sensor order and in any packet order. For example, data may be
received from a first sensor 1 followed by data from a third sensor
followed by data from a second sensor. In another example, a first
packet may be received from a first sensor followed by a first
packet from a second sensor followed by a second packet from the
first sensor. In another example, a second packet from a first
sensor may be received before the first packet of the first sensor
is received. Thus, communications from the sensors may be received
in a quasi-simultaneous manner.
[0039] Timers may be implemented to handle non-responsive sensors,
e.g., for identifying a sensor for maintenance if the sensor has
not responded for a particular period of time or number of cycles.
In an exemplary embodiment, when a sensor responds a time/stamp is
placed on the data and written to a database. This time stamp is
checked every minute (with another timer, not shown) and compared
to the current time. If the device has not responded for a
predetermined period of time, the application generates an alarm.
This alarm can be a visual alarm, an audible alarm, an e-mail being
sent etc.
[0040] FIG. 3 illustrates conceptually the steps performed in
blocks 208 and 210. Blocks 300a-n represent the controls that were
created in the central control computer in block 208. The controls
300a-n establish communication with associated sensors and send
poll data to those sensors (block 210 ). Communication between the
controls 300a-300n are established via the Internet 302. As
illustrated in FIG. 3, multiple controls 300a-n may exist
concurrently (e.g., as multiple threads) for communication with the
sensors. Similar steps may be performed for communicating with
VMS's.
[0041] FIG. 4 is a flow diagram illustrating the receipt of data
from the sensors during the data receiving period that begins at
block 212 (FIG. 2) and ends at block 216. As illustrated in FIG. 4,
communications may be received from multiple sensors 400a-n
concurrently (quasi-simultaneously), e.g., over the Internet 402.
As stated above, each created control (e.g., Winsock control) is
associated with a virtual port. When a sensor checks in, it checks
in through its virtual port. The control for that virtual port then
takes over at block 404, e.g., through a set of application
programming interface routines (API) called by the application to
request and carry out lower-level services performed by the
computer's operating system. The individual controls (represented
by controls 406a-c) process data received at their virtual port
(e.g., using the API) by attaching the address of the sensor and
their virtual port number to the data and passing the data,
address, and virtual port number to a decoding routine 408. The
decoding routine 408 decodes the received data--taking into account
the address and virtual port information--to obtain polling
results. This enables decoding of the data regardless of the order
in which it is received. A similar process may be performed to
receive information from the VMS's. Once the received information
is decoded appropriate action may be taken such as developing
messages and identifying VMS's to display those messages.
[0042] Referring back to FIG. 1, at block 218, one or more VMS's
are identified for updating based on the results received from the
sensors in response to the polling data. For example, if twenty
sensors provide responses to the polling data and, based on those
responses, there are four VMS's to be updated, those four VMS's are
identified for updating. As one example, the information may
indicate that traffic is stopped as detected by sensors "A" and "B"
located at mile 25 of the highway. Once this information is
displayed to an operator the operator may set a single VMS located
along the highway a number of miles upstream of the stopped traffic
to display a message advising the motorists of the situation and
possibly suggesting alternate routes. In accordance with this
example, this VMS would be identified as the sole VMS for
update.
[0043] The central computer may also be programmed to send certain
pre-recorded messages to selected VMS's depending on the status
indication of roadside sensors such as speed or queue detectors.
For example, receipt and decoding by the central control computer
of a message indicating speed of traffic as less than a preset
limit could trigger an automatic response in the form of a command
sent to a VMS setting an appropriate preselected speed limit or a
caution indication. Such messages may constantly change as the data
received by the roadside traffic sensors provide new information
regarding traffic flow, or may change at predetermined desired
intervals.
[0044] At block 220, the application sets a VMS device flag and
indicates the number of VMS's (R) that will be sent message data by
the central control computer. The application then enters a loop,
blocks 220-228, for sequentially establishing communication with
the individual VMS's and sending messages thereto. A counter 221
increments a VMS value M after each pass through the loop. The loop
starts with establishing communication with a first message board
(M=1) and ends after establishing communication with a last message
board (M=R). The message data may be sent using a coding loop
similar to the sample coding loop described above.
[0045] At block 222, a virtual port number and an address for the
VMS are obtained. The virtual port number and the address for the
VMS may be obtained from the table discussed above with reference
to block 202.
[0046] At block 224, a control for the VMS is created at the
central control computer. Parameters such as port number, address,
and a message board string are passed to the control for defining
communications between the central control computer and the VMS. As
described above, the control may be a Windows Socket (Winsock)
control.
[0047] At block 226, the central control computer establishes a
connection with the VMS and sends message data to the message board
through the established connection. As described above, the
connection may be a UDP, TCP/IP, or other such connection. The
message data may include a textual message for display on the VMS
or an indicator that instructs the VMS to display a prerecorded
textual message. In addition, such as in the case of a traffic
metering device VMS, the message data may include timing
information for controlling STOP/GO lights on the traffic metering
device or an indicator that instructs the traffic metering device
to control lights based on predefined timing information.
[0048] At block 228, the application checks if the VMS is the last
VMS (e.g., M=R). If the VMS is the last VMS (e.g., M=R), processing
ends at block 230 (or proceeds at block 204 in a continuous loop
until the application ends). Otherwise, if the VMS is not the last
VMS (e.g., M<R), processing proceeds at block 220 with the steps
of blocks 204-214 repeated for the next VMS.
[0049] In an exemplary embodiment, the VMS's may be polled to
verify that the VMS's are displaying the correct information. In
accordance with this embodiment, the VMS's may be polled using a
routine similar to the routine for polling the sensors described
above with reference to blocks 204-216. All VMS's may be polled to
identify the messages currently being displayed for comparison with
expected messages stored by the central control computer.
Alternatively, only those VMS's that were updated most recently may
be polled.
[0050] When information (e.g., a datagram) is sent over the
Internet from the control computer to the device modems, the
datagram may be broken into smaller packets and sent to the end
device, or the whole datagram may go as one piece. If broken up, it
is reassembled once it gets there. This applies for traffic
traveling from the computer to the devices and from the devices to
the computer. The operating system software on the computer puts
the packets back together if they are broken apart, and the
connecting device modem puts the packets together once they all
reach it. Thus, information going to or coming from more than one
device arrives at or leaves from the computer in a
quasi-simultaneous manner when using more than one port.
[0051] Because data transmitted through the Internet is split into
distinct smaller individual packets arriving at their destination
along various separate routes, because the system does require
confirmation of linking with a device or of successful transmission
of the datagram, and through the use of the virtual ports, the
central control computer is able to poll different roadside devices
without waiting for the complete transmission/reception to and from
each of the roadside devices. This process is referred to herein as
"quasi-simultaneous" as distinguished from a process where the
computer sequentially polls each device, that is, sends out a
message and waits for the completion of the transaction prior to
addressing another roadside device.
[0052] This applies for traffic traveling from the central control
computer to the roadside devices and from the roadside devices to
the central control computer. The central control computer
operating system puts the packets back together if they are broken
apart and the modem attached to the roadside device will put the
packets together once they all reach it.
[0053] The central control computer and the roadside devices are
preferably but not necessarily on what is referred to a permanently
on status. This means that the link between the central control and
the roadside devices is always "on" and there is constant
communication between the central control computer and all of the
devices quasi-simultaneously, thereby providing real time traffic
information. Because the central control computer is always
connected to all the devices it is able to receive information
continuously from all the devices.
[0054] The foregoing system and process have been described with
reference to a Microsoft operating system and routines and
subroutines available through such system. While at present this is
a preferred operating system, the present invention is not to be
limited to use with this operating system exclusively. Rather this
one example of the present invention which is readily implemented
at this time. However other operating systems and subroutines may
be used to create the multiplicity of virtual ports used in
accordance with the present invention to communicate with a
plurality of devices in a quasi-simultaneous fashion through an
Internet connection.
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