Wireless roadway monitoring system

• US 20020177942A1
• Filed: 05/22/2001
• Published: 11/28/2002
• Est. Priority Date: 05/22/2001
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Knaian, Ara N., Paradiso, Joseph A.
• Granted Patent: US 6,662,099 B2
• Time in Patent Office: Days
• US Class Current: 701/117
• CPC Class Codes: G08G 1/02 using treadles built into the road pads or other sensitive devices responsive to passage of vehicles E01F11/00
• CPC Class Codes: G08G 1/042 using inductive or magnetic detectors

Abstract

A wireless, in-road traffic sensor system using sensors that are small, low-cost, and rugged. The sensors may be capable of measuring the speed of passing vehicles, identifying the type of passing vehicle and measuring information about roadway conditions, e.g., wet or icy. The sensor includes a wireless transmitter and may be configured for installation beneath a roadway surface. The sensors may be configured as a traffic sensor system including distributed sensors across a roadway system, concentrators for receiving the sensor broadcasts and a central computer for accumulating and organizing the sensed information. The sensed information may also be made available responsive to user requests via the Web through such reports as traffic delays, alternate route planning and travel time estimates. Alternatively, the sensed information may also be used to control traffic through a traffic control means, such as a traffic signal.

Claims

1. A wireless roadway sensor comprising:

(a) a sensing circuit configured for installation beneath a roadway surface, the sensing element, when so installed, sensing at least one of (i) a vehicle on the roadway passing the sensor, (ii) an average speed of vehicles on the roadway passing the sensor, (iii) types of vehicles on the roadway passing the sensor, (iv) water on the roadway, and (v) ice on the roadway; and

(b) a wireless transmitter, in communication with the sensor, for periodically broadcasting sensed information.

2. The apparatus of claim 1 wherein the sensing element comprises a magnetic-field sensor sensing perturbations in an ambient magnetic field.

3. The apparatus of claim 2 wherein the magnetic-field sensor is a magnetoresistive magnetic field sensor.

5. The apparatus of claim 1 wherein the sensor comprises circuitry for determining an approximate speed of a vehicle on the roadway passing the sensor.

6. The apparatus of claim 5 wherein the speed-determining circuitry comprises first and second magnetic-field sensors, each of the first and the second magnetic-field sensors sensing a vehicle on the roadway passing the respective sensor.

7. The apparatus of claim 6 wherein the speed determining circuitry determines the approximate speed of a vehicle on the roadway passing the sensor responsive to a time difference between sensing a vehicle by the first sensor and sensing of the vehicle by the second sensor.

8. The apparatus of claim 1 further comprising a counter for counting the number of vehicles on the roadway passing the sensor.

9. The apparatus of claim 1 wherein the wireless transmitter is a narrowband transmitter.

10. The apparatus of claim 9 wherein the narrowband transmitter is configured to transmit a frequency-shift-keying signal.

11. The apparatus of claim 1 wherein the wireless transmitter periodically broadcasts sensed information according to a receiverless protocol.

12. The apparatus of claim 11 wherein the receiverless protocol comprises a sparse time-division-multiple-access, randomized-time-of-transmission protocol.

13. The apparatus of claim 1 wherein the wireless transmitter is a spread-spectrum transmitter.

14. The apparatus of claim 1 wherein the wireless transmitter operates substantially within a frequency band spanning 300 MHz to 3,000 MHz.

15. The apparatus of claim 14 wherein the wireless transmitter operates substantially within a frequency band spanning 902 MHz to 928 MHz.

16. The apparatus of claim 1 wherein the sensing element comprises a precipitation sensor for sensing precipitation on the roadway.

17. The apparatus of claim 16 wherein the precipitation sensor comprises circuitry for sensing at least one of permittivity and conductivity.

18. The apparatus of claim 1 wherein the sensor comprises an ice sensor for sensing ice on the roadway.

19. The apparatus of claim 18 wherein the ice sensor comprises circuitry for sensing the temperature of the roadway.

20. The apparatus of claim 1 wherein the sensing element comprises vehicle-detection circuitry for detecting the types of vehicles on the roadway passing the sensor.

21. The apparatus of claim 20 wherein the vehicle-detection circuitry comprises a vibrational sensor for sensing vibrations.

22. The apparatus of claim 21 wherein the vibrational sensor is an acoustic sensor for sensing pressure variations.

23. The apparatus of claim 21 wherein the vibrational sensor is an accelerometer for sensing acceleration.

24. The apparatus of claim 21 wherein the vibrational sensor is an acoustic sensor for sensing pressure variations.

25. The apparatus of claim 1 further comprising diagnostic circuitry for diagnosing sensor status.

26. The apparatus of claim 1 further comprising calibration circuitry.

27. The apparatus of claim 1 wherein the sensor comprises sensing, control and transmission circuitry, the circuitry ordinarily operating in an inactive mode, the sensing circuit being configured to sense an approaching vehicle and in response, to cause the circuitry to enter an active mode.

28. The apparatus of claim 1 wherein the sensing circuit is configured to detect a vehicle over the sensor, the transmitter being configured to suppress transmission when vehicles are overhead.

30. The method of claim 29 wherein the sensor senses vehicles on the roadway passing the sensor through perturbations in an ambient magnetic field.

31. The method of claim 30 wherein the magnetic-field sensor comprises a magnetoresistive magnetic field sensor.

32. The method of claim 29 wherein the sensor determines an approximate speed of a vehicle on the roadway passing the sensor.

33. The method of claim 32 further comprising the step of installing a second sensor beneath the roadway surface, each of the sensors sensing a vehicle on the roadway passing the respective sensor, the sensors being spaced in relation to each other along a baseline, the baseline being substantially collinear with a direction of traffic flow.

34. The method of claim 33 comprising the steps of:

(a) measuring a time difference between a vehicle being sensed at one sensor and the same vehicle being sensed at the other sensor; and

(b) determining the vehicle speed by dividing the baseline separation distance by the measured time difference.

35. The method of claim 29 further comprising the step of counting a number of vehicles on the roadway passing the sensor.

36. The method of claim 29 wherein the step of transmitting sensed information comprises transmitting a narrowband signal.

37. The method of claim 36 wherein the narrowband signal is a frequency-shift-keying signal.

38. The method of claim 29 wherein the step of transmitting sensed information comprises periodically broadcasting sensed information according to a receiverless protocol.

39. The method of claim 38 wherein the receiverless protocol is a sparse time-division-multiple-access protocol.

40. The method of claim 29 wherein the step of transmitting sensed information comprises transmitting a spread-spectrum signal.

41. The method of claim 29 wherein the step of transmitting sensed information comprises transmitting a radio-frequency signal within a frequency band spanning 300 MHz to 3,000 MHz.

42. The method of claim 41 wherein the step of transmitting sensed information comprises transmitting a radio-frequency signal within a frequency band spanning 902 MHz to 928 MHz.

43. The method of claim 29 wherein the sensor senses water through measurement of at least one of permittivity and conductivity.

44. The method of claim 29 wherein vehicles on the roadway passing the sensor are detected by means of an acoustic sensor sensing pressure variations.

46. The apparatus of claim 45 wherein the sensor is configured to sense perturbations in an ambient magnetic field.

47. The apparatus of claim 45 wherein the sensor is configured to sense roadway-surface precipitation.

48. The apparatus of claim 45 wherein the sensor is configured to sense roadway-surface ice.

49. The apparatus of claim 45 wherein the wireless transmitter is a radio frequency transmitter.

50. The apparatus of claim 45 wherein the randomized multiplexing scheme comprises a sparse time-division-multiple-access protocol.

4. The apparatus of 2 further comprising circuitry for adjusting the magnetic-field sensor.

29. A method for sensing roadway information comprising the steps of:

(a) installing a sensor beneath a roadway surface, the sensor, when so installed, sensing at least one of (i) vehicles on the roadway passing the sensor, (ii) an average speed of vehicles on the roadway passing the sensor, (iii) types of vehicles on the roadway passing the sensor, (iv) water on the roadway, and (v) ice on the roadway; and

(b) transmitting sensed information by means of periodic wireless broadcasts.

45. A wireless roadway sensor comprising:

(a) a sensing element configured to sense at least one roadway condition; and

(b) a wireless transmitter in communication with the sensing element, the wireless transmitter being responsive to the sensing element and periodically broadcasting sensed information on a communication channel by means of a randomized multiplexing scheme, the multiplexing scheme allowing the channel to be shared with other sensors broadcasting in accordance with the scheme.

51. A method for sensing roadway information comprising the steps of:

(a) sensing at least one roadway condition; and

(b) transmitting sensed information on a communication channel through periodic wireless broadcasts by means of a randomized multiplexing scheme, the multiplexing scheme allowing the channel to be shared with other sensors broadcasting in accordance with the scheme.

52. The method of claim 51 wherein the sensing step comprises sensing perturbations in an ambient magnetic field.

53. The method of claim 51 wherein the sensing step comprises sensing roadway-surface precipitation.

54. The method of claim 51 wherein the sensing step comprises sensing roadway-surface ice.

55. The method of claim 51 wherein the transmitting step comprises transmitting a wireless radio frequency signal.

56. The method of claim 51 wherein the transmitting step comprises transmitting the sensed information according to a sparse time-division-multiple-access protocol.

58. The system of claim 57 wherein the sensors are configured for installation beneath a roadway surface.

59. The system of claim 57 wherein the computer comprises circuitry for determining traffic volume.

60. The system of claim 57 wherein the computer comprises circuitry for determining traffic congestion.

61. The system of claim 60 wherein the computer comprises circuitry for determining alternate routes responsive to traffic congestion.

62. The system of claim 57 wherein the computer organizing the sensed information obtained by the sensors generates a condition map for the roadway system.

63. The system of claim 62 wherein the computer is a server connected to the Internet and configured to respond to Internet-based requests for information relating to the condition map.

64. The system of claim 62 wherein the condition map encodes time estimates for travel along different segments of the roadway system.

57. A wireless roadway sensing and information-integration system comprising:

(a) a plurality of sensors distributed across a roadway system, the sensors being organized into sets, each of the sets comprising at least one sensor, each of the sensors comprising;

(i) a sensing circuit configured to sense at least one roadway condition; and

(ii) a wireless transmitter responsive to the sensing circuit and periodically broadcasting sensed information;

(b) a plurality of concentrators for receiving the broadcasts, each concentrator receiving broadcasts from the sensors of one of the sets; and

(c) a computer in communication with the concentrators, the computer being configured to accumulate and organize the sensed information obtained by the sensors.

65. A method for controlling traffic comprising the steps of:

(a) installing a sensor beneath a roadway surface, the sensor, when so installed, sensing a roadway condition;

(b) transmitting information relevant to the sensed condition through periodic wireless broadcasts; and

(c) actuating, in accordance with the broadcasts, a traffic-controlling device responsive thereto.

66. The method of claim 65 wherein the sensor senses vehicles on the roadway passing the sensor.

67. The method of claim 65 wherein the sensor senses vehicles by sensing perturbations in an ambient magnetic field.

68. The method of claim 65 wherein the traffic-controlling device comprises a traffic light.

69. The method of claim 65 further comprising the steps of:

(a) installing a plurality of additional sensors beneath the roadway surface at different locations, the sensors, when so installed, sensing the roadway condition and transmitting information relevant to the sensed condition through periodic wireless broadcasts; and

(b) receiving the broadcasts at a concentrator, the traffic controlling device being responsive to the concentrator.