Vehicle detector method for multiple vehicle counting
First Claim
1. A method of estimating the number of vehicles crossing a loop inductor, said method comprising the steps of:
- (a) producing a measuring signal having a succession of values representative of loop inductance referenced to an initial value;
(b) determining a first inflection point of the measuring signal;
(c) establishing a vehicle count threshold value from the value of the measuring signal at the first inflection point;
(d) determining a vehicle count event from the threshold value and the value of the measuring signal at subsequent points of the measuring signal; and
(e) producing a vehicle count estimate from the total number of vehicle count events determined in step (d).
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Accused Products
Abstract
An estimate of the number of vehicles crossing a loop inductor having one or more interconnected discrete loops of the type found in vehicle detector system installations. A measuring signal follows changes in loop inductance caused by the influence of vehicles crossing the loop inductor. A vehicle count threshold value is computed by observing changes in the measuring signal caused by the first car crossing the loop. Subsequent excursions of the measuring signal between relative minima and relative maxima are tested against the threshold and a vehicle count event is registered when the differences exceed the threshold. After a predetermined count period, the number of vehicle counts is estimated from the total count events by multiplying them by an interpolation factor determined empirically from the type of loop inductor. Apparatus for perfoming the method is combined with a conventional vehicle detector system in a switch selectable apparatus for specifying vehicle detector mode or vehicle count mode. The system furhter includes a user selectable circuit for matching the interpolation factor to the type of loop inductor used with the system.
33 Citations
19 Claims
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1. A method of estimating the number of vehicles crossing a loop inductor, said method comprising the steps of:
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(a) producing a measuring signal having a succession of values representative of loop inductance referenced to an initial value; (b) determining a first inflection point of the measuring signal; (c) establishing a vehicle count threshold value from the value of the measuring signal at the first inflection point; (d) determining a vehicle count event from the threshold value and the value of the measuring signal at subsequent points of the measuring signal; and (e) producing a vehicle count estimate from the total number of vehicle count events determined in step (d). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A system for detecting the arrival and departure of vehicles at a location having a loop inductor, said system comprising:
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vehicle sensing means for producing a measuring signal having a succession of values representative of loop inductance referenced to an initial value; means for specifying predetermined vehicle call signal criteria; means for specifying predetermined vehicle count signal criteria; mode selector means for specifying a vehicle detector mode and a vehicle count mode; means for generating vehicle call signals in response to values of said measuring signal meeting the predetermined call signal criteria when the mode selector means specifies the vehicle detector mode; and means for generating vehicle count signals in response to values of said measuring signal meeting predetermined vehicle count signal criteria when the mode selector means specifies the vehicle detector mode. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification