Generalized adaptive signal control method and system

• US 20020116118A1
• Filed: 12/18/2000
• Published: 08/22/2002
• Est. Priority Date: 12/17/1999
• Status: Active Grant

• Current Assignee: Exelis Incorporated (L3Harris Technologies, Inc.)
• Original Assignee: ITT Manufacturing Enterprises, Inc. (ITT, Inc.)
• Inventors: Stallard, Charlie Monroe, Owen, Larry Evans
• Granted Patent: US 6,587,778 B2
• Time in Patent Office: Days
• US Class Current: 701/117
• CPC Class Codes: G08G 1/01 Detecting movement of traffic to be counted or controlled G08G1/07 - G08G1/14 take precedence
• CPC Class Codes: G08G 1/08 according to detected number or speed of vehicles
• CPC Class Codes: G08G 1/082 Controlling the time between beginning of the same phase of a cycle at adjacent intersections
• CPC Class Codes: G08G 1/083 Controlling the allocation of time between phases of a cycle

Abstract

The invention relates to a rule-based method for effective distributed adaptive signal control of traffic networks, and an apparatus using the method. Queue estimates and sets of rules are used to determine the signal state at each intersection in the network. The queue estimation uses real-time data from detectors upstream from an intersection to estimate the number of vehicles approaching the intersection and the vehicles in queue. Each detected vehicle is treated as a group of “partial” vehicles corresponding to approved movements that the vehicle might make. The queue estimation and control logic that determine the signal state can be implemented as a distributed system. The signal control logic consists of a set of rules for uncongested control and a process that creates a fixed time plan for congested control.

Claims

1. A method of controlling traffic at an intersection, comprising:

detecting traffic status;

estimating queue information based on the detected traffic status; and

determining a movement of a vehicle in the intersection by evaluating rules using the estimated queue information; and

controlling a state of a traffic signal to effect the movement.

2. The method of claim 1, wherein the traffic status is detected in real-time.

3. The method of claim 1, wherein the rules include demand rules based on the estimated queue information and a number of vehicles that can exit the queue during said state of the signal;

progression rules based on traffic movements at an adjacent intersection; and

urgency rules based on an amount of time a vehicles waits to move in the intersection.

4. The method of claim 3, wherein the rules include setting a priority for the determined movement, wherein the priority set by the demand rules is based on the queue information and a number of vehicles approaching the intersection but not in the queue.

5. The method of claim 3, wherein the rules include setting a priority for the determined movement, wherein the priority set by the progression rules is based on a number of vehicles approaching the intersection from an adjacent intersection.

6. The method of claim 3, wherein the rules include setting a priority for the determined movement, wherein the priority set by the urgency rules is based on the maximum number of vehicles waiting in the queue at the intersection.

7. The method of claim 1, wherein the rules include setting a priority for the determined movement, and the method further comprising adding the determined movement and the priority to an event scheduler, and selecting from the event scheduler and based on priority a movement for controlling a state of a traffic signal to control the traffic at the intersection.

8. The method of claim 1, wherein a detection zone is a distance along an approach to the intersection having a detector disposed at one end of the detection zone a predetermined distance from the intersection, and the intersection at another end of the intersection, and wherein the detector detects the vehicle when it enters the detection zone, and wherein estimating the queue information is performed by determining a time the vehicle entered the detection zone if the vehicle arrived in the queue at a current time.

9. A traffic controller, comprising:

a detector input unit receiving vehicle measurement data;

a signal state output unit outputting a control signal to control a state of a traffic signal at a first intersection;

a communications port for receiving from another traffic controller traffic information concerning a second intersection; and

a processing unit operating in response to computer program instructions recorded on a medium readable by the processing unit, wherein the processing unit operates to estimate information concerning a queue of vehicles waiting at the first intersection, generates a control signal for controlling the state of the traffic signal based on traffic movement rules, the estimated queue information and the traffic information received from the second traffic controller.

10. The traffic controller of claim 9, wherein the processing unit operates in response to computer program instructions recorded on a medium readable by the processing unit.

11. The traffic controller of claim 9, wherein the detector input unit receives the vehicle measurement data in real-time.

12. The traffic controller of claim 9, wherein the rules include rules based on demand at the first intersection, on progression of vehicles from the second intersection, and an amount of time vehicles have been waiting at the first intersection.

15. The computer program of claim 14, wherein the computer code for detecting the vehicle approaching the intersection operates using real-time vehicle measurement data.

16. The computer program of claim 14, wherein the traffic control rules include rules based on demand at the first intersection, on progression of vehicles from the second intersection, and an amount of time vehicles have been waiting at the first intersection.

19. The method of claim 18, further comprising placing the designated movement and the determined priority on an event list to schedule the designated movement for execution.

13. A method of automatically estimating information concerning a queue of vehicles within a detection zone having an entry point and an exit point, the queue having a front and back, the method comprising:

detecting a time a vehicle crosses the entry point of the detection zone;

calculating a time the vehicle would have entered the detection zone if the vehicle is located at the back of the queue at a current time;

comparing the detected entry time with the calculated entry time; and

determining that the vehicle has arrived at the back of the queue at the current time if the calculated entry time is greater than the detected entry time.

14. A computer-readable medium of instructions having a computer program for controlling a traffic controller connected to a traffic signal for controlling traffic at an intersection;

the computer program comprising;

a data structure representing an approach to the intersection;

a data structure representing a partial vehicle, wherein a partial vehicle represents a portion of an entire vehicle approaching the intersection on the approach the portion, the portion relating to a probability of the vehicle traveling over a predetermined movement in the intersection;

computer code for detecting the vehicle approaching the intersection on the approach;

computer code for estimating, based on measured vehicle arrival data, a queue information relating to vehicles on the approach waiting at the intersection;

computer code for applying traffic control rules to the estimated queue information to generate a recommended movement in the intersection;

computer code for selecting the recommended movement, among other recommended movements, and controlling the state of the traffic signal according to the selected movement.

17. A method of automatically estimating information concerning a queue of vehicles at an approach to an intersection, the queue being within a detection zone having an entry point and an exit point, the queue having a front and back, and where the approach is for the vehicles in the queue to move in the intersection across an opposing approach to the intersection, the method comprising:

estimating a number of vehicles in the queue;

estimating a time gap between vehicles traveling in the opposing approach;

determining if the estimated time gap is sufficiently large to allow the vehicles in the queue to complete the movement across the intersection.

18. A method of generating a request for a movement of items in a node in response to a state of a control signal, the method comprising:

selecting a type of movement of an item in the node;

designating the selected movement as a recommended movement if the number of items in a queue for the selected movement cannot exit the queue while the control signal is in said state; and

designating a movement with the largest queue if the number of items in the queue for the selected movement can exit the queue while the control signal is in said state; and

determining a priority for the designated movement based on a length of the queue.

20. A method of generating a request for a movement of items in a present node in response to a state of a control signal, the method comprising:

detecting if a control signal for a node adjacent to the present node changes states within a predetermined time;

for each type of movement in the present node setting a priority for the movement based on the number of items expected to approach the present node from the adjacent node and the percentage of items that are expected to make the movement in the present node.

21. The method of claim 20, further comprising, for each type of movement in the present node, setting a time to evaluate executing the movement according to the priority of the movement based on an amount of time for an item to travel from the adjacent node to the present node.

22. A method of generating a request for a movement of items in a present node in response to a state of a control signal, the method comprising:

detecting if a number of items in an approach to a node exceeds a threshold;

setting a priority for a movement of an item in the node, wherein the priority is based on the number of items in the approach to the node, if the detected number of items exceeds the threshold; and

scheduling the movement for execution based on the priority of the movement.

23. The method of claim 22, further comprising, scheduling the movement for execution only if the detected number of items exceeds the threshold for a predetermined amount of time.