Vehicle traffic monitoring using cellular telephone location and velocity data

• US 6,810,321 B1
• Filed: 03/17/2003
• Issued: 10/26/2004
• Est. Priority Date: 03/17/2003
• Status: Expired due to Term

• Current Assignee: T-Mobile Innovations LLC (Deutsche Telekom AG)
• Original Assignee: Sprint Communications Company LP (Deutsche Telekom AG)
• Inventors: Cook, Fred S.
• Primary Examiner(s): LOUIS JACQUES, JACQUES H
• Application Number:
  US10/390,307
• Time in Patent Office: 589 Days
• Field of Search: 340/933, 340/935, 340/995.13, 340/988-993, 340/901-905, 340/910-912, 340/934, 340/936, 455/414.2, 455/414.3, 455/456.1, 455/456.2, 455/456.3, 455/456.5, 455/456.6, 455/457, 701/117-119, 701/200-201, 701/207-210, 701/25-26
• US Class Current: 701/117
• CPC Class Codes: G08G 1/0104 Measuring and analyzing of parameters relative to traffic conditions

Abstract

A vehicular traffic monitoring system communicates with a plurality of mobile communication devices carried in moving vehicles and capable of determining their respective geographic positions and velocities. A data collector receives data samples from the plurality of mobile communication devices, each data sample comprising instantaneous location and velocity information of a respective mobile telephone at a respective time. A road segment identifier is coupled to the data at the collector for matching data samples wherein a respective instantaneous location corresponds to one of a plurality of road segments monitored by the traffic monitoring system. A sliding average calculator coupled to the road segment identifier determines an average speed corresponding to matched data samples for a particular one of the road segments in response to a predetermined sliding window. A state change detector coupled to the sliding average calculator detects a traffic state change at the road segment in response to the average speed in the predetermined sliding window determined at first and second times. A congestion alerting mechanism coupled to the state change detector routes notifications when the respective road segment state changes (either to a congested state or a clear state).

Claims

1. A vehicular traffic monitoring system for communicating with a plurality of mobile telephones carried in moving vehicles and capable of determining their respective geographic positions and velocities, comprising:

a data collector for receiving data samples from said plurality of mobile telephones, each data sample comprising instantaneous location and velocity information of a respective mobile telephone at a respective time;

a road segment identifier coupled to said data collector for finding matching data samples wherein a respective instantaneous location corresponds to one of a plurality of road segments monitored by said traffic monitoring system;

a recursive sliding average calculator coupled to said road segment identifier for determining an average speed corresponding to matched data samples for a particular one of said road segments in response to a predetermined sliding window having a predetermined number of said matched data samples wherein said average speed is determined as a recursive sliding average A_n in response to an nth one of said matched data samples S_n, a previous average speed A<sub>n−

1</sub>, and a predetermined number W of matched data samples in said predetermined sliding window;

a state change detector coupled to said recursive sliding average calculator for detecting a traffic state change at said road segment in response to said average speed in said predetermined sliding window determined at first and second times; and

a congestion indicator coupled to said state change detector, said congestion indicator indicating either a congested state or a clear state of said respective road segment in response to said detected traffic state change.

2. The traffic monitoring system of claim 1 further comprising:

a notification system coupled to said congestion indicator for informing at least some of said moving vehicles to avoid a respective road segment when its respective congestion indicator indicates a congested state.

3. The traffic monitoring system of claim 1 further comprising:

a route calculator coupled to said congestion indicator for determining a preferred route between a current position and a desired destination provided in a route request from a user, said preferred route avoiding any of said road segments for which a respective congestion indicator indicates a congested state.

4. The traffic monitoring system of claim 1 further comprising:

an interval identifier coupled to said road segment identifier for determining a respective recurring time-of-day interval of said data samples for a respective road segment;

an averager coupled to said interval identifier for determining an overall average speed corresponding to said data samples for said recurring time-of-day interval; and

a baseline database storing baseline averages corresponding to a plurality of said recurring time-of-day intervals for said plurality of road segments.

5. The traffic monitoring system of claim 4 further comprising:

a route calculator coupled to said baseline database for determining a preferred route between a current position and a desired destination provided in a route request from a user, said preferred route being determined in response to said baseline averages of said road segments for a respective time-of-day interval corresponding to said route request.

6. The traffic monitoring system of claim 4 further comprising:

a route calculator coupled to said baseline database and said congestion indicator for determining a preferred route between a current position and a desired destination provided in a route request from a user, said preferred route avoiding any of said road segments for which a respective congestion indicator indicates a congested state, and said preferred route being determined in response to said baseline averages of said road segments for a respective time-of-day interval corresponding to said route request.

7. The traffic monitoring system of claim 1 wherein said mobile telephones operate within a wireless cellular network, wherein each one of said data samples is obtained from a respective mobile telephone during a registration operation to said wireless cellular network, and wherein said data collector is coupled to said wireless cellular network for initiating registration operations for selected mobile telephones.

8. The traffic monitoring system of claim 1 wherein said state change detector calculates a difference between said average speeds determined at first and second times and compares said difference with a threshold to detect said traffic state change.

9. The traffic monitoring system of claim 1 wherein said state change detector includes a cache for storing a plurality of said average speeds during a predetermined period including said first and second times, wherein said state change detector identifies a maximum average speed and a minimum average speed within said cache, and wherein said traffic state change is detected when a difference in relative magnitude of said maximum average speed and said minimum average speed is greater than a threshold.

10. The traffic monitoring system of claim 1 wherein said average speed is determined by said recursive sliding average calculator according to a recursive formula comprising:

$A_n=\frac{A_{n-1}<br><br>\left(W-1\right)+S_n}{W}.$

11. A method of monitoring vehicular traffic on a plurality of road segments, said method comprising the steps of:

receiving data samples from a plurality of mobile telephones carried in moving vehicles and capable of determining their respective geographic positions and velocities, each data sample comprising instantaneous location and velocity information of a respective mobile telephone at a respective time;

matching data samples with respective road segments whenever a respective instantaneous location corresponds to a stored location of a respective one of said road segments;

determining an average speed corresponding to a recursive average of said matched data samples for a particular one of said road segments in response to a predetermined sliding window having a predetermined number of said matched data samples wherein said average speed is determined as a recursive sliding average A_n in response to an nth one of said matched data samples S_n, a previous average speed A<sub>n−

1</sub>, and a predetermined number W of matched data samples in said predetermined sliding window;

detecting a traffic state change at said road segment in response to a change in said average speed in said predetermined sliding window determined at first and second times; and

indicating either a congested state or a clear state of said respective road segment in response to said detected traffic state change.

12. The method of claim 11 further comprising the step of informing at least some of said moving vehicles to avoid a respective road segment when its respective congestion indicator indicates a congested state.

13. The method of claim 11 further comprising the step of determining a preferred route between a current position and a desired destination specified in a route request from a user, said preferred route avoiding any of said road segments for which a respective congestion indicator indicates a congested state.

14. The method of claim 11 further comprising the steps of:

determining a respective recurring time-of-day interval of said data samples for a respective road segment;

determining an overall average speed corresponding to said data samples for said recurring time-of-day interval; and

storing baseline averages corresponding to a plurality of said recurring time-of-day intervals for said plurality of road segments.

15. The method of claim 14 further comprising the step of determining a preferred route between a current position and a desired destination specified in a route request from a user, said preferred route being determined in response to said baseline averages of said road segments for a respective time-of-day interval corresponding to said route request.

16. The method of claim 14 further comprising the step of determining a preferred route between a current position and a desired destination specified in a route request from a user, said preferred route avoiding any of said road segments for which a respective congestion indicator indicates a congested state, and said preferred route being determined in response to said baseline averages of said road segments for a respective time-of-day interval corresponding to said route request.

17. The method of claim 11 wherein said mobile telephones operate within a wireless cellular network, wherein each one of said data samples is obtained from a respective mobile telephone during a registration operation to said wireless cellular network, and wherein said data collector is coupled to said wireless cellular network for initiating registration operations for selected mobile telephones.

18. The method of claim 11 wherein said step of detecting a traffic state change is comprised of:

calculating a difference between said average speeds determined at first and second times; and

comparing said difference with a threshold.

19. The method of claim 11 wherein said step of detecting a traffic state change is comprised of:

storing in a cache a plurality of said average speeds during a predetermined period including said first and second times;

identifying a maximum average speed and a minimum average speed within said cache; and

detecting whether a difference in relative magnitude of said maximum average speed and said minimum average speed is greater than a threshold.

20. The method of claim 11 wherein said recursive average is determined according to a recursive formula comprising:

$A_n=\frac{A_{n-1}<br><br>\left(W-1\right)+S_n}{W}.$