External adaptive control systems and methods

• US 8,103,436 B1
• Filed: 09/24/2008
• Issued: 01/24/2012
• Est. Priority Date: 11/26/2007
• Status: Active Grant

• Current Assignee: Rhythm Engineering
• Original Assignee: Rhythm Engineering
• Inventors: Chandra, Reggie J., Bley, James W., Penrod, Stephen S., Parker, Arthur S.
• Primary Examiner(s): Beauchaine, Mark
• Application Number:
  US12/236,698
• Time in Patent Office: 1,217 Days
• Field of Search: 340/911, 340/912, 701/118
• US Class Current: 701/117
• CPC Class Codes: G08G 1/07 Controlling traffic signals
• CPC Class Codes: G08G 1/081 Plural intersections under common control

Abstract

An external adaptive control system controls a traffic signal at a critical intersection that has a most conflicting volume of traffic among volumes of traffic at intersections in a traffic network. The external adaptive control system determines a plan identifying a guaranteed green light time and a minimum green duration and a period for the plan. The external adaptive control system determines, based on the plan, a non-linear schedule with one or more states corresponding to one or more individual phases with each state having a state start time and a state duration. Queues for individual traffic movements at the critical intersection also may be used to determine the non-linear schedule. The adaptive external control system controls the traffic signal according to the non-linear schedule. The external adaptive control system transmits its plan to one or more other external adaptive control systems for other intersections. The other external adaptive control systems determine other plans based on the plan from the external adaptive control system and an expected travel time between the critical intersection and the corresponding intersection.

Claims

1. A method for controlling traffic movements for a plurality of traffic intersections each having a volume of traffic comprising:

determining a critical intersection having a most conflicting volume from among the volumes;

determining a plan comprising at least one guaranteed green time and at least one minimum green duration for at least one direction of traffic movement at the critical intersection and a period for the plan;

determining other plans each comprising another guaranteed green time and another minimum green duration for another intersection based on the at least one guaranteed green time and the at least one minimum green duration at the critical intersection and an expected travel time between the critical intersection and the other intersection, each other plan having another period;

determining at least one non-linear schedule for the critical intersection at an external adaptive control system based on the plan and queue lengths for individual phases at the critical intersection, the non-linear schedule comprising a plurality of states having a variable order, each state having a state start time and a state duration;

determining other non-linear schedules for the other intersections at other external adaptive control systems based on the other plans and other queue lengths for other individual phases for the other intersections, each other non-linear schedule comprising another plurality of other states having another state order, each other state having another state start time and another state duration;

controlling at least one traffic signal controller assembly at the critical intersection by the external adaptive control system according to the at least one non-linear schedule; and

controlling other traffic signal controller assemblies at the other intersections by the other external adaptive control systems according to the other non-linear schedules.

2. The method of claim 1 wherein controlling the at least one traffic signal controller assembly according to the at least one non-linear schedule comprises:

sequentially generating presence data at the external adaptive control system for each state in the non-linear schedule in the variable order starting at each state start time and for each state duration; and

sequentially transmitting the presence data corresponding to each state at each state start time and for each corresponding state duration from the external adaptive control system for reception by the at least one traffic signal controller assembly in a fully actuated mode.

3. The method of claim 2 wherein the presence data for each state corresponds to detector calls for up to two individual phases for each state.

4. The method of claim 2 wherein transmitting the presence data corresponding to each state comprises transmitting a communication for the presence data for each state comprising data corresponding to presence of at least one vehicle in each of up to two individual phases for each state.

5. The method of claim 4 further comprising:

configuring the at least one traffic signal controller assembly with an input output card for receiving each communication; and

configuring the at least one traffic signal controller assembly with a detector card to format each communication into a form processable by a controller unit in the traffic signal controller assembly.

6. The method of claim 1 wherein controlling the other traffic signal controller assemblies according to the other non-linear schedules comprises:

sequentially generating corresponding other presence data at each corresponding other external adaptive control system for corresponding other states in corresponding other non-linear schedules in corresponding other variable orders starting at corresponding other state start times and for corresponding other state durations; and

sequentially transmitting the corresponding other presence data for each corresponding other state at each corresponding other state start time and for each corresponding other state duration from each corresponding other external adaptive control system for reception by a corresponding other traffic signal controller assembly in a fully actuated mode.

7. The method of claim 6 wherein transmitting the corresponding other presence data for each corresponding other state comprises transmitting a communication for each corresponding other presence data for each corresponding other state comprising data corresponding to presence of at least one vehicle in each of up to two individual phases for each other state.

8. The method of claim 1 further comprising:

receiving detector data at the at least one external adaptive control system from a plurality of detectors; and

determining the queue lengths for the individual phases for which the detector data was received.

9. The method of claim 8 wherein:

at least one of the detectors comprises at least one member of a group consisting of a loop detector, a video camera detector, and a puck (magnetic) detector.

10. The method of claim 8 wherein the external adaptive control system comprises historical data comprising prior light states generated by the at least one traffic signal controller assembly for particular individual phases for a configured time frame, and the method further comprises:

determining when at least some detector data is not received at the external adaptive control system; and

determining the at least one non-linear schedule at the external adaptive control system based on the plan, and at least some of the historical data, the at least some historical data used in place of at least some queue lengths for the not received detector data.

11. The method of claim 8 further comprising:

receiving, at the external adaptive control system from the at least one traffic signal controller assembly, a plurality of light states generated by the traffic signal controller assembly for particular individual phases for a configured time frame;

storing the plurality of light states as historical data in memory at the external adaptive control system; and

when at least some of the detector data is not received at the external adaptive control system, processing at least some of the historical data in place of at least some of the detector data in an emergency mode to determine the non-linear schedule.

12. The method of claim 8 further comprising:

receiving other detector data at the other external adaptive control systems from another plurality of other detectors;

determining the other queue lengths for the other individual phases for which the other detector data was received.

13. The method of claim 1 wherein determining the plan comprises:

determining a number of vehicles per second passing through the critical intersection in the at least one direction of traffic movement during a prior period;

multiplying the number of vehicles per second by the prior period to determine an expected number of vehicles to pass through the critical intersection in the selected direction during the plan; and

multiplying a clearance time by the expected number of vehicles to determine the minimum green duration for the plan.

14. The method of claim 1 wherein determining the plan comprises determining the guaranteed green time to be a starting time of the plan.

15. The method of claim 1 wherein determining the plan comprises:

determining a number of vehicles per second passing through the critical intersection in the at least one direction of traffic movement during a time frame the at least one direction of traffic movement has a right-of-way in a prior period;

multiplying the number of vehicles per second by the prior period to determine an expected number of vehicles to pass through the critical intersection in the selected direction during the plan; and

multiplying a clearance time by the expected number of vehicles to determine the minimum green duration for the plan.

16. The method of claim 1 wherein determining the period comprises:

reducing the period from a prior period by a first selected time amount when a non-selected direction of traffic movement at the critical intersection has more than enough time during the prior period to clear traffic for at least one corresponding individual phase in the non-selected direction; and

increasing the period from the prior period by a second selected time amount when the non-selected direction of traffic movement at the critical intersection does not have than enough time during the prior period to clear the traffic for the at least one corresponding individual phase in the non-selected direction.

17. The method of claim 1 wherein determining the period comprises:

reducing the period from a prior period by a first selected time amount when the selected direction of traffic movement at the critical intersection has more than enough time during the prior period to clear traffic for at least one corresponding individual phase in the selected direction; and

increasing the period from the prior period by a second selected time amount when the selected direction of traffic movement at the critical intersection does not have than enough time during the prior period to clear the traffic for the at least one corresponding individual phase in the selected direction.

18. The method of claim 1 wherein:

determining the plan further comprises determining at least one second guaranteed green time and at least one second minimum green duration for a coordinated direction of traffic movement at the critical intersection; and

determining the at least one non-linear schedule for the critical intersection at the external adaptive control system comprises determining the at least one non-linear schedule based on the queue lengths and the plan with the at least one guaranteed green time, the at least one green duration, the at least one second guaranteed green time, the at least one second minimum green duration, and the period for the plan.

19. The method of claim 1 wherein:

determining the other plans further comprises determining, for each corresponding other plan, a corresponding other guaranteed green time, a corresponding other green duration, at least one second corresponding guaranteed green time, and at least one second corresponding minimum green duration for a coordinated direction of traffic movement at a corresponding intersection, each corresponding other plan having a corresponding other period; and

determining the other non-linear schedules for the other intersections at the other external adaptive control system comprises, for each other non-linear schedule, determining the other non-linear schedule based on corresponding queue lengths at the corresponding intersection and the corresponding other plan.

20. The method of claim 1 further comprising:

receiving progression data at the external adaptive control system for at least one progression, the progression data comprising at least one number of vehicles approaching the critical intersection and at least one progression time for the at least one number of vehicles approaching the critical intersection; and

determining the at least one non-linear schedule at the external adaptive control system based on the plan, the queue lengths, and the progression data.

21. The method of claim 1 further comprising:

transmitting the plan from the at least one external adaptive control system to the other external adaptive control systems.

22. The method of claim 1 further comprising:

transmitting progression data from the at least one external adaptive control system to at least one of the other external adaptive control systems.

23. The method of claim 1 further comprising:

determining the non-linear schedule by determining first states, first state start times, and first state durations for a main direction;

determining second states, second state start times, and second state durations for a cross street direction; and

ordering the first states and second states in a variable order.

24. The method of claim 1 further comprising determining the non-linear schedule by:

establishing a start time for the non-linear schedule and an end time for the non-linear schedule;

determining a first partial schedule by marking time occupied by coordinated phases as committed;

for each individual phase with an unaccounted queue, determine a plurality of potential schedules from the first partial schedule by fitting the unaccounted individual phase into areas where no non-compatible phase already exists;

applying a scoring function to each potential schedule, the scoring function comprising multiplying each queue length for each unaccounted individual phase by a waiting time for the unaccounted individual phase and summing each multiplied queue length and waiting time to obtain a score for each potential schedule;

selecting the potential schedule with a lowest score as the non-linear schedule;

filling at least one empty area in the schedule with at least one compatible individual phase; and

generating the non-linear schedule from the potential schedule with the lowest score and the at least one compatible individual phase.

25. The method of claim 1 further comprising:

determining a plurality of potential solutions for a main direction and a cross street direction for the non-linear schedule based on the queue lengths at the critical intersection, each potential solution having transition times and waiting times for a plurality of potential state sequences;

selecting a solution for each direction having a lowest waiting time and a shortest transition time; and

generating the non-linear schedule with the selected main street solution and the selected cross street solution.

26. The method of claim 1 wherein at least one of the other external adaptive control systems for at least one of the other intersections is upstream from the external adaptive control system at the critical intersection, and the method further comprises determining at least one other guaranteed green time for at least one of the other plans at the at least one other external adaptive control system to be the guaranteed green time minus the expected travel time between the critical intersection and the at least one of the other intersections.

27. The method of claim 1 wherein at least one of the other external adaptive control systems for at least one of the other intersections is upstream from the external adaptive control system at the critical intersection, and the method further comprises determining at least one other guaranteed green time for at least one of the other plans at the at least one other external adaptive control system to be the guaranteed green time minus the expected travel time between the critical intersection and the at least one of the other intersections and a clearance time at the at least one of the other intersections.

28. The method of claim 1 wherein at least one of the other external adaptive control systems for at least one of the other intersections is downstream from the external adaptive control system at the critical intersection, and the method further comprises determining at least one other guaranteed green time for at least one of the other plans at the at least one other external adaptive control system to be the guaranteed green time plus the expected travel time between the critical intersection and the at least one of the other intersections.

29. The method of claim 1 wherein at least one of the other external adaptive control systems for at least one of the other intersections is downstream from the external adaptive control system at the critical intersection, and the method further comprises determining at least one other guaranteed green time for at least one of the other plans at the at least one other external adaptive control system to be the guaranteed green time plus the expected travel time between the critical intersection and the at least one of the other intersections and a clearance time at the critical intersection.

30. A method for controlling traffic movements for a plurality of traffic intersections each having a volume of traffic comprising:

determining a critical intersection for a main street having a most conflicting volume from among the volumes;

determining a plan comprising at least one guaranteed green time and at least one minimum green duration for at least one direction of traffic movement at the critical intersection;

determining other plans each comprising another guaranteed green time and another minimum green duration for another intersection based on the at least one guaranteed green time and the at least one minimum green duration at the critical intersection and an expected travel time between the critical intersection and the other intersection;

determining at least one non-linear schedule for the critical intersection at an external adaptive control system based on the at least one guaranteed green time, the at least one minimum green duration, the period, and queue lengths for individual phases at the critical intersection, the non-linear schedule comprising a plurality of states having a variable order, each state having a state start time and a state duration;

determining other non-linear schedules for the other intersections at other external adaptive control systems based on the other guaranteed green times, other minimum green durations, and other queue lengths for other individual phases for other intersections, each other non-linear schedule comprising another plurality of other states having another state order for a corresponding other intersection, each other state having another state start time and another state duration;

sequentially generating presence data at the external adaptive control system for each state in the non-linear schedule in the variable order starting at each state start time and for each state duration and sequentially transmitting the presence data corresponding to each state at each state start time and for each corresponding state duration from the external adaptive control system for reception by at least one traffic signal controller assembly; and

sequentially generating other presence data at the other external adaptive control systems for other states in the other non-linear schedules in the other variable orders starting at the other state start times and for the other state durations and sequentially transmitting the other presence data corresponding to each other state at each other state start time and for each other state duration from each corresponding other external adaptive control system for reception by a corresponding other traffic signal controller assembly.

31. The method of claim 30 wherein transmitting the presence data corresponding to each state comprises transmitting a communication for each presence data for each state comprising data corresponding to presence of at least one vehicle in each of up to two individual phases for each state.

32. The method of claim 30 wherein transmitting the other presence data for each other state comprises transmitting a communication for each other presence data for each other state comprising data corresponding to presence of at least one vehicle in each of up to two individual phases for each other state.

33. The method of claim 32 further comprising:

receiving detector data at the at least one external adaptive control system from a plurality of detectors; and

determining the queue lengths for the individual phases for which the detector data was received.

34. The method of claim 30 wherein the external adaptive control system comprises historical data comprising prior light states generated by the at least one traffic signal controller assembly for particular individual phases for a configured time frame, and the method further comprises:

determining when at least some detector data is not received at the external adaptive control system; and

determining the at least one non-linear schedule at the external adaptive control system based on the at least one guaranteed green time, the at least one minimum green duration, and at least some of the historical data, the at least some historical data used in place of at least some queue lengths for the not received detector data.

35. The method of claim 30 further comprising:

receiving, at the external adaptive control system from the at least one traffic signal controller assembly, a plurality of light states generated by the traffic signal controller assembly for particular individual phases for a configured time frame;

storing the plurality of light states as historical data in memory at the external adaptive control system; and

when at least some of the detector data is not received at the external adaptive control system, processing at least some of the historical data in place of at least some of the detector data in an emergency mode to determine the non-linear schedule.

36. The method of claim 30 further comprising:

receiving other detector data at the other external adaptive control systems from another plurality of other detectors; and

determining the other queue lengths for the other individual phase for which the other detector data was received.

37. The method of claim 30 further comprising:

determining the non-linear schedule by determining first states, first state start times, and first state durations for a main direction;

determining second states, second state start times, and second state durations for a cross street direction; and

ordering the first states and second states in a variable order.

38. The method of claim 30 further comprising:

determining a plurality of potential solutions for a main direction and a cross street direction for the non-linear schedule based on the queue lengths at the critical intersection, each potential solution having transition times and waiting times for a plurality of potential state sequences;

selecting a solution for each direction having a lowest waiting time and a shortest transition time; and

generating the non-linear schedule with the selected main street solution and the selected cross street solution.

39. A method for controlling traffic movements for a plurality of traffic intersections each having a volume of traffic comprising:

determining a critical intersection having a most conflicting volume from among the volumes;

determining a plan with at least one guaranteed green time and at least one minimum green duration for at least one direction of traffic movement at the critical intersection;

determining other guaranteed green times and other minimum green durations for other intersections based on the at least one guaranteed green time and the at least one minimum green duration at the critical intersection and an expected travel time between the critical intersection and the other intersections;

determining at least one schedule for the critical intersection at an external adaptive control system based on the at least one guaranteed green time and the at least one minimum green duration, the schedule comprising a plurality of states having a variable order;

determining other schedules for the other intersections at other external adaptive control systems based on the other guaranteed green times, each other schedule comprising another plurality of other states having another variable order;

controlling at least one traffic signal controller assembly at the critical intersection by the external adaptive control system according to the at least one schedule; and

controlling other traffic signal controller assemblies at the other intersections by the other external adaptive control systems according to the other schedules.

40. The method of claim 39 wherein controlling the at least one traffic signal controller assembly according to the at least schedule comprises:

sequentially generating presence data at the external adaptive control system for each state in the schedule in the variable order starting at each state start time and for each state duration; and

for each presence data corresponding to each state at each state start time and for each corresponding state duration, transmitting a communication from the external adaptive control system for reception by the at least one traffic signal controller assembly comprising data corresponding to presence of at least one vehicle in each of up to two individual phases for each state.

41. The method of claim 39 wherein controlling the other traffic signal controller assemblies according to the other schedules comprises:

sequentially generating corresponding other presence data at each corresponding other external adaptive control system for corresponding other states in corresponding other schedules in corresponding other variable orders starting at corresponding other state start times and for corresponding other state durations; and

for each other presence data corresponding to each other state at each other state start time and for each corresponding other state duration, transmitting a communication from the external adaptive control system for reception by a corresponding other traffic signal controller assembly comprising data corresponding to presence of at least one vehicle in each of up to two individual phases for each other state.

42. The method of claim 39 further comprising:

receiving detector data at the at least one external adaptive control system from a plurality of detectors;

determining a queue length corresponding to each individual phase for which the detector data was received; and

determining the at least one schedule at the external adaptive control system based on the at least one guaranteed green time, the at least one minimum green duration, and the queue lengths.

43. The method of claim 42 wherein the external adaptive control system comprises historical data comprising prior light states generated by the at least one traffic signal controller assembly for particular individual phases for a configured time frame, and the method further comprises:

determining when at least some detector data is not received at the external adaptive control system; and

determining the at least one schedule at the external adaptive control system based on the at least one guaranteed green time, the at least one minimum green duration, and at least some of the historical data, the at least some historical data used in place of the not received detector data.

44. The method of claim 39 further comprising:

receiving, at the external adaptive control system from the at least one traffic signal controller assembly, a plurality of light states generated by the traffic signal controller assembly for particular individual phases for a configured time frame;

storing the plurality of light states as historical data in memory at the external adaptive control system;

processing at least some of the historical data with the at least one guaranteed green time and the at least one minimum green time to determine the schedule.

45. The method of claim 39 further comprising:

receiving other detector data at the other external adaptive control systems from another plurality of other detectors;

determining other queue lengths corresponding to each other individual phase for which the other detector data was received; and

determining the other schedules at the external adaptive control system based on the at least one guaranteed green time, the at least one minimum green duration, and the other queue lengths.

46. The method of claim 39 further comprising:

determining a period for the plan, the period comprising a time frame between the at least one guaranteed green time at the critical intersection and a second guaranteed green time for the at least one direction of traffic movement at the critical intersection; and

determining the at least one schedule at the external adaptive control system based on the at least one guaranteed green time, the at least one minimum green duration, and the period.

47. The method of claim 39 further comprising:

determining the schedule by determining first states, first state start times, and first state durations for a main direction;

determining second states, second state start times, and second state durations for a cross street direction; and

ordering the first states and second states in a variable order.

48. The method of claim 39 further comprising:

determining a plurality of potential solutions for a main direction and a cross street direction for the schedule based on queue lengths at the critical intersection, each potential solution having transition times and waiting times for a plurality of potential state sequences;

selecting from the plurality of potential solutions a main direction solution having a lowest waiting time and a shortest transition time;

selecting from the plurality of potential solutions a cross street direction solution having a lowest waiting time and a shortest transition time; and

generating the schedule with the selected main direction solution and the selected cross street direction solution.

49. A system for controlling traffic movements for a plurality of traffic intersections each having a volume of traffic, the system comprising:

an external adaptive control system at a critical intersection having a most conflicting volume from among the volumes and configured to;

determine a plan comprising at least one guaranteed green time and at least one minimum green duration for at least one direction of traffic movement at the critical intersection and a period for the plan;

determine at least one non-linear schedule for the critical intersection based on the plan and queue lengths for individual phases at the critical intersection, the non-linear schedule comprising a plurality of states having a variable order, each state having a state start time and a state duration; and

control at least one traffic signal controller assembly at the critical intersection according to the at least one non-linear schedule; and

a plurality of other external adaptive control systems, each other external adaptive control system configured to;

determine a corresponding plan, each corresponding plan comprising a corresponding guaranteed green time and a corresponding minimum green duration for a corresponding intersection based on the at least one guaranteed green time and the at least one minimum green duration at the critical intersection and an expected travel time between the critical intersection and the corresponding intersection, each corresponding plan having a corresponding period;

determine a corresponding non-linear schedule for the corresponding intersection based on the corresponding plan and corresponding queue lengths for corresponding individual phases for the corresponding intersection, each corresponding non-linear schedule comprising another plurality of corresponding states having a corresponding state order, each corresponding state having a corresponding state start time and a corresponding state duration; and

control a corresponding traffic signal controller assembly at the corresponding intersection according to the corresponding non-linear schedule.

50. The system of claim 49, wherein the at least one traffic controller assembly is configured in a fully actuated mode and the external adaptive control system is configured to:

sequentially generate presence data for each state in the non-linear schedule in the variable order starting at each state start time and for each state duration; and

sequentially transmit the presence data corresponding to each state at each state start time and for each state duration from the external adaptive control system for reception by the at least one traffic signal controller assembly in the fully actuated mode.

51. The system of claim 50 wherein the presence data corresponding to each state comprises a communication comprising data corresponding to presence of at least one vehicle in each of up to two individual phases for each state.

52. The system of claim 49 wherein the external adaptive control system comprises historical data comprising prior light states generated by the at least one traffic signal controller assembly for particular individual phases for a configured time frame, and the external adaptive control system further is configured to:

determine when at least some detector data is not received at the external adaptive control system; and

determine the at least one non-linear schedule at the external adaptive control system based on the plan, and at least some of the historical data, the at least some historical data used in place of at least some queue lengths for the not received detector data.

53. The system of claim 49 wherein the external adaptive control system is configured to:

receive, from the at least one traffic signal controller assembly, a plurality of light states generated by the traffic signal controller assembly for particular individual phases for a configured time frame;

store the plurality of light states as historical data in memory at the external adaptive control system; and

when at least some of the detector data is not received at the external adaptive control system, process at least some of the historical data in place of at least some of the detector data in an emergency mode to determine the non-linear schedule.

54. The system of claim 49 wherein the external adaptive control system is configured to determine the plan by:

determining a number of vehicles per second passing through the critical intersection in the at least one direction of traffic movement during a prior period;

multiplying the number of vehicles per second by the prior period to determine an expected number of vehicles to pass through the critical intersection in the selected direction during the plan; and

multiplying a clearance time by the expected number of vehicles to determine the minimum green duration for the plan.

55. The system of claim 49 wherein the external adaptive control system is configured to determine the plan by:

determining a number of vehicles per second passing through the critical intersection in the at least one direction of traffic movement during a time frame the at least one direction of traffic movement has a right-of-way in a prior period;

multiplying the number of vehicles per second by the prior period to determine an expected number of vehicles to pass through the critical intersection in the selected direction during the plan; and

multiplying a clearance time by the expected number of vehicles to determine the minimum green duration for the plan.

56. The system of claim 49 wherein the external adaptive control system is configured to determine the plan by determining the guaranteed green time to be a starting time of the plan.

57. The system of claim 49 wherein the external adaptive control system is configured to determine the period by:

reducing the period from a prior period by a first selected time amount when a non-selected direction of traffic movement at the critical intersection has more than enough time during the prior period to clear traffic for at least one corresponding individual phase in the non-selected direction; and

increasing the period from the prior period by a second selected time amount when the non-selected direction of traffic movement at the critical intersection does not have enough time during the prior period to clear the traffic for the at least one corresponding individual phase in the non-selected direction.

58. The system of claim 49 wherein the external adaptive control system is configured to determine the period by:

reducing the period from a prior period by a first selected time amount when the selected direction of traffic movement at the critical intersection has more than enough time during the prior period to clear traffic for at least one corresponding individual phase in the selected direction; and

increasing the period from the prior period by a second selected time amount when the selected direction of traffic movement at the critical intersection does not have enough time during the prior period to clear the traffic for the at least one corresponding individual phase in the selected direction.

59. The system of claim 49 wherein the external adaptive control system is configured to determine the non-linear schedule by determining first states, first state start times, and first state durations for a main direction, determining second states, second state start times, and second state durations for a cross street direction, and ordering the first states and second states in the variable order.

60. The system of claim 49 wherein the external adaptive control system is configured to determine the non-linear schedule by:

establishing a start time for the non-linear schedule and an end time for the non-linear schedule;

determining a first partial schedule by marking time occupied by coordinated phases as committed;

for each individual phase with an unaccounted queue, determine a plurality of potential schedules from the first partial schedule by fitting the unaccounted individual phase into areas where no non-compatible phase already exists;

applying a scoring function to each potential schedule, the scoring function comprising multiplying each queue length for each unaccounted individual phase by a waiting time for the unaccounted individual phase and summing each multiplied queue length and waiting time to obtain a score for each potential schedule;

selecting the potential schedule with a lowest score as the non-linear schedule;

filling at least one empty area in the schedule with at least one compatible individual phase; and

generating the non-linear schedule from the potential schedule with the lowest score and the at least one compatible individual phase.

61. The system of claim 49 wherein the external adaptive control system is configured to determine a plurality of potential solutions for a main direction and a cross street direction based on the queue lengths, each potential solution having transition times and waiting times for a plurality of potential state sequences, to select from the plurality of potential solutions a main direction solution having a lowest waiting time and a shortest transition time, to select from the plurality of potential solutions a cross street direction solution having a lowest waiting time and a shortest transition time, and to generate the non-linear schedule with the selected main direction solution and the selected cross street direction solution.

62. The system of claim 49 the external adaptive control system is configured to:

determine the plan by determining at least one second guaranteed green time and at least one second minimum green duration for a coordinated direction of traffic movement at the critical intersection; and

determine the at least one non-linear schedule for the critical intersection at the external adaptive control system by determining the at least one non-linear schedule based on the queue lengths and the plan with the at least one guaranteed green time, the at least one green duration, the at least one second guaranteed green time, the at least one second minimum green duration, and the period for the plan.

63. The system of claim 49 wherein the other external adaptive control systems are configured to:

determine the other plans by determining, for each corresponding other plan, a corresponding other guaranteed green time, a corresponding other green duration, at least one second corresponding guaranteed green time, and at least one second corresponding minimum green duration for a coordinated direction of traffic movement at a corresponding intersection, each corresponding other plan having a corresponding other period; and

determine the other non-linear schedules for the other intersections by determining, for each other non-linear schedule, the other non-linear schedule based on corresponding queue lengths at the corresponding intersection and the corresponding other plan.

64. The system of claim 49 wherein at least one of the other external adaptive control systems for at least one of the other intersections is upstream from the external adaptive control system at the critical intersection, and the at least one of the other external adaptive control systems is configured to determine at least one other guaranteed green time for at least one of the other plans to be the guaranteed green time minus the expected travel time between the critical intersection and the at least one of the other intersections.

65. The system of claim 49 wherein at least one of the other external adaptive control systems for at least one of the other intersections is upstream from the external adaptive control system at the critical intersection, and the at least one of the other external adaptive control systems is configured to determine at least one other guaranteed green time for at least one of the other plans to be the guaranteed green time minus the expected travel time between the critical intersection and the at least one of the other intersections and a clearance time at the at least one of the other intersections.

66. The system of claim 49 wherein at least one of the other external adaptive control systems for at least one of the other intersections is downstream from the external adaptive control system at the critical intersection, and the at least one of the other external adaptive control systems is configured to determine at least one other guaranteed green time for at least one of the other plans to be the guaranteed green time plus the expected travel time between the critical intersection and the at least one of the other intersections.

67. The system of claim 49 wherein at least one of the other external adaptive control systems for at least one of the other intersections is downstream from the external adaptive control system at the critical intersection, and the at least one of the other external adaptive control systems is configured to determine at least one other guaranteed green time for at least one of the other plans to be the guaranteed green time plus the expected travel time between the critical intersection and the at least one of the other intersections and a clearance time at the critical intersection.

68. The system of claim 49 wherein each other external adaptive control system is configured to:

sequentially generate corresponding presence data for the corresponding states in the corresponding non-linear schedule in the corresponding variable order starting at the corresponding state start times and for the corresponding state durations; and

sequentially transmit the corresponding presence data corresponding to each corresponding state at each corresponding state start time and for each corresponding state duration for reception by the corresponding traffic signal controller assembly.

69. A system for controlling traffic movements for a plurality of traffic intersections each having a volume of traffic, the system comprising:

an external adaptive control system at a critical intersection having a most conflicting volume from among the volumes and configured to;

determine a plan comprising at least one guaranteed green time and at least one minimum green duration for at least one direction of traffic movement at the critical intersection and a period for the plan;

determine at least one non-linear schedule for the critical intersection based on the at least one guaranteed green time, the at least one minimum green duration, the period, and queue lengths for individual phases at the critical intersection, the non-linear schedule comprising a plurality of states having a variable order, each state having a state start time and a state duration;

sequentially generate presence data for each state in the non-linear schedule in the variable order starting at the state start time and for the state duration; and

sequentially transmit the presence data corresponding to each state at the state start time and for the corresponding state duration from the external adaptive control system for reception by at least one traffic signal controller assembly; and

a plurality of other external adaptive control systems at other intersections configured to;

determine other plans each comprising another guaranteed green time and another minimum green duration for another intersection based on the at least one guaranteed green time and the at least one minimum green duration at the critical intersection and an expected travel time between the critical intersection and the other intersection;

determine other non-linear schedules for the other intersections based on the other guaranteed green times, other minimum green durations, and other queue lengths for other individual phases for the other intersections, each other non-linear schedule comprising another plurality of other states having another state order for a corresponding other intersection, each other state having another state start time and another state duration;

sequentially generate other presence data for other states in the other non-linear schedules in the other variable orders starting at the other state start times and for the other state durations; and

sequentially transmit the other presence data corresponding to each other state at each other state start time and for each other state duration for reception by a corresponding other traffic signal controller assembly.

70. The system of claim 69 wherein the at least one traffic signal controller assembly is configured in a fully actuated mode and the external adaptive control system is configured to transmit the presence data corresponding to each state by transmitting a communication for the presence data for each state for reception by the at least one traffic signal controller assembly in the fully actuated mode, each communication comprising data corresponding to presence of at least one vehicle in each of up to two individual phases for each state.

71. The system of claim 69 wherein the external adaptive control system comprises historical data comprising prior light states generated by the at least one traffic signal controller assembly for particular individual phases for a configured time frame, and the external adaptive control system further is configured to:

determine when at least some detector data is not received at the external adaptive control system; and

determine the at least one non-linear schedule at the external adaptive control system based on the plan, and at least some of the historical data, the at least some historical data used in place of at least some queue lengths for the not received detector data.

72. The system of claim 69 wherein the external adaptive control system is configured to:

receive, from the at least one traffic signal controller assembly, a plurality of light states generated by the traffic signal controller assembly for particular individual phases for a configured time frame;

store the plurality of light states as historical data in memory at the external adaptive control system; and

when at least some of the detector data is not received at the external adaptive control system, process at least some of the historical data in place of at least some of the detector data in an emergency mode to determine the non-linear schedule.

73. The system of claim 69 wherein the external adaptive control system is configured to determine the plan by:

determining a number of vehicles per second passing through the critical intersection in the at least one direction of traffic movement during a prior period;

multiplying the number of vehicles per second by the prior period to determine an expected number of vehicles to pass through the critical intersection in the selected direction during the plan; and

multiplying a clearance time by the expected number of vehicles to determine the minimum green duration for the plan.

74. The system of claim 69 wherein the external adaptive control system is configured to determine the plan by:

determining a number of vehicles per second passing through the critical intersection in the at least one direction of traffic movement during a time frame the at least one direction of traffic movement has a right-of-way in a prior period;

multiplying the number of vehicles per second by the prior period to determine an expected number of vehicles to pass through the critical intersection in the selected direction during the plan; and

multiplying a clearance time by the expected number of vehicles to determine the minimum green duration for the plan.

75. A system for controlling traffic movements for a plurality of traffic intersections each having a volume of traffic, the system comprising:

an external adaptive control system for a critical intersection having a most conflicting volume from among the volumes and configured to;

determine a plan with at least one guaranteed green time and at least one minimum green duration for at least one direction of traffic movement at the critical intersection;

determine at least one schedule for the critical intersection based on the at least one guaranteed green time and the at least one minimum green duration, the at least one schedule comprising a plurality of states in a variable order; and

control at least one traffic signal controller assembly at the critical intersection according to the at least one schedule; and

a plurality of other external adaptive control systems configured to;

determine other guaranteed green times and other minimum green durations for other intersections based on the at least one guaranteed green time and the at least one minimum green duration at the critical intersection and an expected travel time between the critical intersection and the other intersections;

determine other schedules for the other intersections at other external adaptive control systems based on the other guaranteed green times and the other minimum green durations, each other schedule comprising another plurality of other states in another variable order; and

control other traffic signal controller assemblies at the other intersections according to the other schedules.