Method and system for mapping traffic congestion

• US 20020077742A1
• Filed: 08/31/2001
• Published: 06/20/2002
• Est. Priority Date: 03/08/1999
• Status: Active Grant

• Current Assignee: Josef Mintz
• Original Assignee: Josef Mintz
• Inventors: Mintz, Josef
• Granted Patent: US 6,532,414 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

Abstract

This invention provides a system and method for mapping parameters of a traffic congestion, for example, a road congestion, relative to a focus. Mapping of the road congestion may include determination of an average length of the road congestion over a time interval, motion rate in the road congestion and arrival rate to the road congestion. These parameters, in turn, maybe used to determine an expected delay in traveling throughout the road congestion as well as trends, i.e., changes with time, in the road congestion. The mapping is performed relative to the mapping focus, typically the front end of a road congestion. The mapping system may construct snapshots of mapping samples received from a small percentage of predesignated probes, e.g., a small percentage of vehicles equipped with an appropriate receiver and transmitter. The mapping samples are preferably received in response to predefined broadcast queries sent from the mapping system. The determination of the average length of a road congestion may be based on a direct approach, obviating the need to estimate discrete lengths of the road congestion, in dynamic conditions that may include variations in the arrival rate of vehicles to the road congestion and the departure rate of vehicles from the congestion over time.

Claims

1. A method of determining an indication of length of a queue of vehicles on a road, using probe reports of probes transmitted according to a predetermined protocol, associated with the probe reports, to a mapping system which processes the probe reports, wherein a report includes a characteristic value of position of the probe, the method comprising:

(a) constructing with the mapping system a plurality of mapping samples,

(b) determining for each of the plurality of mapping samples a position that relates to the farthest probe position from a mapping focus;

(c) choosing from the position determined in (b) the position which is the farthest from the mapping focus for determining an indication on length of the queue.

2. A method according to claim 1, wherein the position determined in (b) is the position of the farthest probe from the mapping focus.

3. A method according to claim 1, further comprising a step of transmitting a response to reporters that disables transmitters that did not transmit a report within a chosen range in the constructed mapping sample from continuing to report, according to a predetermined procedure, and after construction of one of the plurality of a mapping samples.

4. A method according to claim 3, wherein the chosen range includes the position of the farthest probe.

6. A method according to claim 1, wherein the indication on the length of said queue is substantially determined by the farthest chosen position in the constructed mapping samples.

7. A method according to claim 1, wherein resolution of the position reports acquired from the probes is determined according to predetermined occupation length of vehicles in a queue of vehicles in different traffic conditions.

8. A method according to claim 1, further comprising the step of obtaining at least two different reports from at least one probe for determining the length of a queue of vehicles.

9. A method according to claim 1, wherein the number of plurality of mapping samples is in the range of 3 to 7 for a respective expected range of 2.5 to 5 percent in average percentage of probes and wherein time interval between consecutive mapping samples is a typical traffic light cycle in the mapped area.

10. A method according to claim 1, wherein the at least one mapping sample is determined by predetermined data storage according to average motion over a time period and according to estimated probability of probe arrival and according to estimated arrival rate of vehicles.

11. A method according to claim 10, wherein according to a predetermined procedure the mapping system estimates the probability of probe arrival according to a percentage of probes among arrived vehicles to the queue, the method comprising:

(a) concatenating a plurality of non-overlapping segments of consecutive mapping samples according to motion between mapping samples

(b) determining the number of vehicles in the concatenated segments by the ratio of the length of the concatenated segments to expected occupation length of vehicles in the queue

(c) determining by a statistical estimator the percentage of probes based on the distribution of the accumulated probes identified over the period relevant to mapping samples of concatenated segments.

12. A method according to claim 11, wherein the data storage is optimized to provide the number of mapping samples to produce substantially the minimum expected error in the determined indication on length of the queue compared to the real average length of the queue according to the respective mapping samples.

13. A method according to claim 1, wherein at a time prior to determining the indication on the length of the queue mapping samples are adjusted according to a predetermined procedure that virtually adjusts the position of the mapping focus in the mapping samples in order to remove differences between motion rate and average arrival rate.

14. A method according to claim 13, wherein at a time after determining indication on the length of the queue the determined indication is adjusted by a value which is indicative of the prior adjustments that were made to the mapping samples in order to remove effect of prior adjustments upon the mapping samples.

15. A method according to claim 1, wherein successive new indications on length of a queue are determined according to a procedure that includes the successive newest mapping samples.

16. A method according to claim 15, wherein a one dimensional median filter is applied to the successive indications on length of the queue.

17. A method according to claim 1, wherein mapping samples are collected according to required resolution of the determination of length of said queue determined by departure rate of vehicles from the queue.

18. A method according to claim 1, wherein mapping samples collected from a road controlled by traffic lights are collected substantially at times respective to the times when the traffic lights change to the green setting.

19. A method according to claim 1, wherein the number of vehicles in a lane segment of said queue is determined according to estimated occupation length of the vehicles.

21. A method according to claim 1, wherein the characteristic value of a position is an indication on the distance of a reporter from the mapping focus.

22. A method according to claim 1, wherein a said mapping sample constructed by reports transmitted to the mapping system within a response time synchronized to the mapping system and to the reporters.

23. A method according to claim 22, wherein a report of a position characteristic value is a signal transmitted by at least one probe in a slot of the response time that is indicative on a range of positions.

24. A method according to claim 22, wherein the time of the position related reports is determined by a broadcast query to the probes.

25. A method according to claim 3, wherein after a disabling response the mapping system receives new reports and constructs a second mapping sample comprised of new reports.

26. A method according to claim 1, wherein the mapping system determines the length of motion toward mapping focus by calculating range characteristic value for a range in a mapping sample subsequent to a disabling response, which includes the position characteristic value indicative of the closest position to the mapping focus and calculating the difference between the said range characteristic value and the range characteristic value of the corresponding chosen range in earlier mapping sample.

27. A method according to claim 26, wherein according to motion towards mapping focus the mapping system determines non occupied space expected between vehicles along the queue.

28. A method according to claim 18, wherein the time when substantially the traffic light system changes to the green setting is identified by the mapping system through reports from probes.

29. A method according to claim 1, wherein according to a predetermined procedure the mapping system estimates arrival rate to the queue, the method further comprising:

(a) concatenating a plurality of non overlapping segments of consecutive mapping samples according to the two position related reports,

(b) determining time interval between two time of arrival reports corresponding to two position related reports,

(c) determining average arrival rate in terms of segment length occupied by arriving vehicles between successive mapping samples by calculating the ratio of the total length of concatenated segment, in relation to the number of concatenated mapping samples.

30. A method according to claim 29, wherein the number of concatenated mapping samples is substantially limited to elapsed time interval in which the average arrival rate of probes to the queue is expected to be stationary.

31. A method according to claim 29, wherein the length of motion of non disabled reporter towards mapping focus between two consecutive mapping samples determines the point between consecutive concatenated segments.

33. A method according to claim 3, further comprising the step of obtaining at least two different reports from at least one probe for determining the length of queue.

35. A method according to claim 21, wherein time correlated mapping samples are collected according to required resolution of the determination of length of said queue determined by departure rate of vehicles from the queue.

37. A method according to claim 21, wherein mapping samples collected from a road controlled by traffic lights are collected substantially at times respective to the times when the traffic lights change to the green setting.

38. A method according to claim 26, wherein the number of vehicles in a lane segment of said queue is determined according to estimated occupation length of the vehicles.

39. A method according to claim 29, wherein the number of vehicles in a lane segment of said queue is determined according to estimated occupation length of the vehicles.

47. A method according to claim 10, wherein the mapping system determines the length of motion toward mapping focus by calculating range characteristic value for a range in a mapping sample subsequent to a disabling response, which includes the position characteristic value indicative of the closest position to the mapping focus and calculating the difference between the said range characteristic value and the range characteristic value of the corresponding chosen range in earlier mapping sample.

48. A method according to claim 26, wherein the mapping system determines the departure rate from the mapping focus in congested road in units of length of congested road segment per unit of time according to the determined length of motion towards mapping focus.

49. A method according to claim 10, wherein according to a predetermined procedure the mapping system estimates arrival rate to the queue, the method further comprising:

(a) concatenating a plurality of non overlapping segments of consecutive mapping samples according to the two position related reports,

(b) determining time interval between two time of arrival reports corresponding to two position related reports,

(c) determining average arrival rate in terms of segment length occupied by arriving vehicles between successive mapping samples by calculating the ratio of the total length of concatenated segment, in relation to the number of concatenated mapping samples.

5. A method of determining length of a queue of vehicles on a road and traffic motion in the queue, wherein according to a predetermined protocol probes report characteristic values of the position of the probes to a receiver of mapping system which processes the reports, the method comprising:

(a) constructing at least one mapping sample that includes at least one of the reports,

(b) determining a range of the position characteristic values in which the farthest reporter from mapping focus was identified in the mapping sample constructed in (a);

(c) transmitting to reporters a response that according to a predetermined procedure disables transmitters that did not transmit a report within the chosen range from continuing to report;

(d) receiving further reports and constructing a subsequent mapping sample;

(e) repeating steps (a) to (d) according to a predetermined procedure;

(f) choosing from the determined ranges in (b) the farthest chosen range to be indicative of the length of the queue;

(g) determining motion length toward a mapping focus by calculating a range characteristic value for a range in a mapping sample, subsequent to the first mapping sample, which includes the position characteristic value indicative of the closest position to the mapping focus and calculating the difference between the said range characteristic value and the range characteristic value of a corresponding chosen range in an earlier mapping sample.

50. A method according to claim 5 wherein the determined range in (b) is substantially the characteristic value of position of the farthest probe.

20. A method of creating conditions which enable assessment of traffic motion rate in a queue of vehicles and enables to construct reference positions for further concatenation of non overlapped segments of mapping sample to further enable more accurate statistical estimates, including either or both average arrival rate of vehicles to the queue and percentage of probes in the queue, wherein according to a predetermined protocol probes report characteristic values of their position to a mapping system which receives and processes the reports, the method comprising:

(a) constructing a first mapping sample that includes at least one of said reports,

(b) determining a range of said position characteristic values in which at least one of said reports was identified in the first mapping sample,

(c) transmitting to reporters a response that according to a predetermined procedure disables transmitters that did not transmit a report within the chosen range of the first mapping sample from continuing to report.

32. A method according to claim 20, wherein resolution of the position reports acquired from the probes is determined according to occupation length of vehicles in congested road in different traffic conditions.

34. A method according to claim 20, wherein time correlated mapping samples are collected according to required resolution of the determination of length of said queue determined by departure rate of vehicles from the said queue.

36. A method according to claim 20, wherein mapping samples collected from a road controlled by traffic lights are collected substantially at times respective to the times when the traffic lights change to the green setting.

40. A method according to claim 20, wherein the characteristic value of a position is an indication on the distance of a reporter from the mapping focus.

41. A method according to 20, wherein a said mapping sample constructed by reports transmitted to the mapping system within a response time synchronized to the mapping system and to the reporters.

42. A method according to claim 20, wherein the chosen range in which reporters are not disabled includes the position of the farthest reporter from the mapping focus.

43. A method according to claim 20, wherein the transmitted response to disable transmitters is a message comprising mapping sample that according to predetermined procedure reporters disable their transmitters from continuing to report if they did not transmit a report within a range in the mapping sample chosen according to the predetermined procedure.

44. A method according to claim 20, wherein after disabling at least one of the transmitters, the probe enables the transmitter of the probe by a predetermined procedure at a time it passed the mapping focus.

45. A method according to claim 20, wherein a non disabled reporter reports a time indication respective to its arrival to the reported position.

46. A method according to claim 20, wherein after a disabling response the mapping system receives new reports and constructs a second mapping sample comprised of new reports.