HIGHWAY VEHICLE SENSOR SYSTEM

• US 3,641,569 A
• Filed: 10/01/1970
• Issued: 02/08/1972
• Est. Priority Date: 10/01/1970
• Status: Expired due to Term

• Current Assignee: David Bushnell, Joseph J. Oliver, Roger L. Fuller
• Original Assignee: David Bushnell, Joseph J. Oliver, Roger L. Fuller
• Inventors: Bushnell, David, FUller, Roger L., Oliver, Joseph J.
• Primary Examiner(s): Cooper, William C.
• Application Number:
  US05/077,155
• Time in Patent Office: 495 Days
• Field of Search: 340/38L,31A
• US Class Current: 340/941
• CPC Class Codes: G08G 1/015 with provision for distinguishing between two or more types of vehicles, e.g. between motor-cars and cycles

Abstract

A highway vehicle sensor, consisting of a main loop energized with low radiofrequency energy and having side legs spaced apart a predetermined distance, is buried in the surface of a highway. Around each side leg is a probe loop in which a signal is generated by the presence of a vehicle over the probe loop. The two output signals from the two probe loops are processed to determine vehicle presence, direction of travel, speed and length and headway between vehicles on the highway.

Claims

1. A highway vehicle sensor comprising a. a field generating element having two extended legs adapted to be spaced along a highway;

b. means for energizing said main element to produce a field around each leg of a magnitude to project above the surface of such highway; and

c. a probe located closely adjacent each of said legs, each such probe being adapted to generate a signal upon a variation in the field of its adjacent side leg produced by the presence of a vehicle in the immediate proximity of said leg.

2. A sensor as in claim 1 in which said energizing means comprises a source of radiofrequency energy.

3. A sensor as in claim 1 in which said field-generating element comprises a loop.

4. A sensor as in claim 1 in which each probe comprises a loop about the adjacent leg of said field-generating element.

5. A highway vehicle sensor system comprising a. a pair of sensor elements spaced along a highway;

b. means for producing a field adjacent to each sensor element and projecting above the highway in the path of vehicles to be sensed;

c. each sensor element being adapted to generate a signal in response to a change in said field produced by the presence of a vehicle in said field; and

d. means for measuring the time interval between corresponding predetermined portions of said two signals.

6. A system as in claim 5 in which are provided a. means for determining the order in which said two signals are produced by the passage of a vehicle;

and b. means for deriving from said order an indication of the direction of travel of said vehicle along said highway.

7. A system as in claim 5 in which means are provided for determining the speed of a vehicle travelling along said highway;

said latter means comprising data processing means for dividing the distance between said sensors by said time interval whereby the output of said data processing means represents said speed.

8. A system as in claim 7 in which means are provided for determining the length of said vehicle, said latter means comprising a. means for measuring the time duration of one of said two signals;

and b. data processing means for multiplying said time duration by the speed of said vehicle as determined in claim 7, whereby the output of said latter data processing means represents said length.

9. A system as in claim 5 in which the means for producing said field comprises a field-generating element having two extended legs spaced along said highway and said sensor elements are respectively located adjacent to said legs.

10. A system as in claim 9 in which the source of radiofrequency energy is connected to said field-generating element for generating said field.