Importance

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Abstract

An improved detector is provided for installation in a roadway surface. The detector finds utility in a highway vehicle detection system for determining vehicle presence, vehicle speed and vehicle length. First and second matched induction coil magnetic sensors are maintained at or near the roadway surface. Each of the sensors has a longitudinal axis aligned normal to the roadway surface. The first and second sensors are separated from one another by a known distance in a direction substantially aligned with a direction of traffic flow. Each of the sensors generate a differential magnetic field signature with respect to time to indicate a passing vehicle's leading and trailing edge magnetic signatures. Vehicle speed is determined by a time-distance relationship using the leading and trailing edge magnetic signatures and the known distance. Vehicle length is determined by a time-speed relationship using the leading and trailing edge magnetic signatures and the determined vehicle speed. A triaxial magnetometer maintained at a location in close proximity to the first and second sensors measures a DC magnetic field. The DC magnetic field has vertical and horizontal magnetic field components with the horizontal components including a component substantially aligned with the direction of traffic flow and a component substantially perpendicular to the direction of traffic flow. The vertical and horizontal components caused by the passing vehicle are used to determine vehicle presence. An ELF communications system may be incorporated with the detector to link roadside and vehicle transmitted/received information.

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First Claim