APPARATUS FOR DETECTING TRAFFIC INFORMATION

• US 3,675,195 A
• Filed: 11/18/1969
• Issued: 07/04/1972
• Est. Priority Date: 11/29/1968
• Status: Expired due to Term

• Current Assignee: Ryohei Kawasaki, Shunsuke Iwamoto
• Original Assignee: Ryohei Kawasaki, Shunsuke Iwamoto
• Inventors: Iwamoto, Shunsuke, Kawasaki, Ryohei
• Primary Examiner(s): Claffy, Kathleen H.
• Assistant Examiner(s): Myers, Randall P.
• Application Number:
  US04/877,803
• Time in Patent Office: 959 Days
• Field of Search: 340/38R,38L,38S
• US Class Current: 340/941
• CPC Class Codes: G01V 3/102 by measuring amplitude
• CPC Class Codes: G08G 1/042 using inductive or magnetic detectors

Abstract

Apparatus for detecting traffic information employs as a vehicle detector a composite inductance loop laid on a road of which traffic information is to be detected. The composite loop consists of a series combination of a large loop portion and a small loop portion. When a vehicle enters the small loop portion, the composite loop suffers a first pulse-like change in the inductance value thereof. As the vehicle moves from the small into the large loop portion the inductance value of the composite loop is reduced to a level lower than the level of the first pulse-like change and kept substantially at that level so long as the vehicle remains inside the large loop portion. When the vehicle is passing the opposite end of the large loop portion, the inductance value thereof again suffers a pulse-like change which is smaller than the first pulse-like change. From such changes in the inductance of the composite loop it will be possible to know traffic informations such as traffic volume, traffic density, vehicle speed, etc. The system may be provided with means for compensating for changes in the inductance of the composite loop caused by changes in environmental conditions.

Claims

1. An apparatus for detecting vehicles on a street and providing an output signal useful for obtaining various types of traffic information therefrom, including traffic volume, traffic density, vehicle speed and the like, comprising:

a. a composite inductance loop comprising a large loop portion and a small loop portion, said portions being connected in series, said composite inductance loop being installed in said street such that said large and small loop portions cover different detection areas thereof, and b. a detecting means connected to said composite inductance loop to produce said output signal in response to changes in the inductance value of said composite inductance loop caused by the presence of a vehicle in said detection areas on said street.

2. The apparatus of claim 1, wherein the relative lengths of said large and small loop portions are such that the detection area of said large loop portion extends over a much greater length of said street than the detection area of said small loop portion.

3. The apparatus of claim 1, further including means coupled to said detecting means for indicating the value of said output signal as a vehicle passes through said detection areas.

4. The apparatus of claim 1, wherein said detecting means produces a pulse-like output signal in response to the presence of a vehicle in the detection area provided by said small loop portion, and further including means for counting the number of said pulse-like output signals.

5. ThE apparatus of claim 4, further including a differentiator connected to the output of said detecting means to differentiate the pulse-like output signals therefrom to produce corresponding differentiated pulses, and wherein said counting means comprises a pulse counter for counting the number of said differentiated pulses.

6. The apparatus of claim 1, wherein said detecting means produces a pulse-like output signal in response to the presence of a vehicle in the detection area provided by said small loop portion, and further including a differentiator connected to the output of said detecting means to differentiate the pulse-like output signals therefrom to produce corresponding differentiated pulses, and a determining means for enabling the operation of a means compensating for changes in the output of said detecting means when said output exceeds a predetermined compensation level and none of said differentiated pulses have been produced for a predetermined period of time.