Patent ID: 6208268
Filing Date: 2001-03-27
Classification: G08G

Abstract:
A highway vehicle sensing system comprising:vehicle speed and length detection means including first and second matched induction coil magnetic sensors maintained at or near a roadway surface, each of said sensors having a longitudinal axis aligned normal to the roadway surface, said sensors being separated from one an oher by a known distance in a direction substantially aligned with a direction of traffic flow, each of said sensors generating a differential magnetic field signature with respect to time to indicate a passing vehicle's leading and trailing edge magnetic signatures, wherein said leading and trailing edge magnetic signatures are used in conjunction with said known distance to determine vehicle speed and vehicle length; andvehicle presence detection means, including a triaxial magnetometer maintained at a location in close proximity to said first and second sensors, for measuring a DC magnetic field at said location to determine vehicle presence, said DC magnetic field having vertical and horizontal magnetic field components with said horizontal components including a component substantially aligned with the direction of traffic flow and a component substantially perpendicular to the direction of traffic flow, wherein said vertical and horizontal components caused by the passing vehicle are used to determine vehicle presence.