FEASIBILITY DEMONSTRATION OF A LATERAL POSITION INDICATION SYSTEM BASED ON MAGNETIC PAVEMENT MARKING TAPE

This paper reports the results of a feasibility demonstration of a lateral position indication system for vehicles based on permanently magnetized pavement marking tape, carried out at the MnROAD test facility. The magnetic tape offers a durable, economically attractive alternative to burying individual magnetic markers within the road bed. Magnetic tape was installed next to both edge lines on approximately 2 km of the 4 km circumference closed loop test road at the MnROAD pavement test facility. The tape used for the installation consisted of a 102 mm width brown-black magnetic tape, edge laminated next to a contrasting 25 mm width of white reflective pavement marking material. A magnetic field sensor assembly containing three magnetoresistive elements oriented in orthogonal directions and a one dimensional CCD array of optical sensors were mounted on a test vehicle. An algorithm was developed and implemented in real time to convert the magnetic field measurements as the vehicle traveled along the tape into an estimate of lateral position. Accuracy was determined by comparison with optical measurements. Reliable estimates of position were obtained for lateral displacements up to about one meter. A high concentration of buried ferromagnetic objects producing magnetic "noise" made the Mn/ROAD site particularly challenging for a magnetic detection system. Performance on ordinary roads that are typically "cleaner" magnetically should be as good or better.