Digital Vehicle Detector

Claim 2

In combination with a plurality of traffic lanes leading to an intersection, a vehicle detection and traffic control system comprising a plurality of detection loops mounted in respective traffic lanes for inductive coaction with vehicles approaching the intersection, respective oscillators operatively connected to the loops so that said loops control the periods of the oscillators and so that said periods are changed by vehicles on said lanes approaching said intersection, time-sharing means to sequentially scan the oscillator outputs, means to derive data corresponding to the periods of the oscillators, respective memories associated with the oscillators, means to store the time-shared data in said respective memories, means to compare data furnished to the memories with previously stored data therein and to derive comparison data, traffic signal means, and means including time-sharing decoding means to furnish commands to said traffic signal means in accordance with the comparison data.

Claim 3

The vehicle detection and traffic control system of claim 1, and wherein the derived, stored and comparison data is in digital form.

Claim 4

The vehicle detection and traffic control system of claim 2, and means to prevent commands to said traffic signal means unless said comparison data exceeds a predetermined lower limit digital value.

Claim 5

The vehicle detection and traffic control system of claim 3, and means for variably presetting said lower limit value.

Claim 6

The vehicle detection and traffic control system of claim 3, and means to limit the length of time that a vehicle is allowed to indicate its presence over a loop and maintain a command to said traffic signal means.

Claim 7

The vehicle detection and traffic control system of claim 3, and means to substitute the last-derived digital comparison data for the previously stored digital comparison data in the associated memory after a predetermined time period and to terminate its command to said traffic signal means.

Claim 8

The vehicle detection and traffic control system of claim 6, and means for variably presetting said time period.

Claim 9

The vehicle detection and traffic control system of claim 6, aNd wherein said substitution means comprises a decrementing digital presence timer settable to a maximum timing value, and means to set said timer to maximum responsive to the detection of movement of a vehicle over a loop, whereby to maintain its command during said timing value while such movement continues.

Claim 10

The vehicle detection and control system of claim 8, and means to provide a small negative drift to said associated memory, comprising a binary decrementing counter decremented each computational cycle and connected to said memory and including means to provide a downward drift rate proportional to said lower limit value divided by the timer setting.

Claim 11

The vehicle detection and traffic control system of claim 1, wherein the derived, stored and comparison data is in digital form, means to prevent commands to said traffic signal means unless said comparison data exceeds a predetermined lower limit digital value, and means to substitute the last-derived digital comparison data for the previously stored digital comparison data in the associated memory after a predetermined time period and to terminate its command to said traffic signal means, wherein said substitution means comprises a decrementing digital presence timer settable to a maximum timing value, means to set said timer to maximum responsive to the detection of movement of a vehicle to a position over a loop, whereby to maintain its command during said timing value, means to terminate said command at the end of said maximum timing value if no further movement of the vehicle occurs, and means to reset said timer to maximum when the vehicle resumes movement before the end of said maximum timing value.

Claim 12

The vehicle detection and traffic control system of claim 1, and wherein each detection loop comprises an inductor arranged to define a plurality of adjacent elongated detection areas extending in the direction of the associated traffic lane.

Claim 13

The vehicle detection and traffic control system of claim 11, and wherein each detection loop is arranged to define three elongated side-by-side detection areas.