A magnetic signpost AVM system with limited dead reckoning

An automatic vehicle monitoring (AVM) system employing magnetic signposts imbedded in the roadway has been designed and tested. It has been augmented by a technique for detecting turns of approximately 90°. Combined in a hybrid AVM system, the two techniques provide great accuracy and high reliability with lower signpost density than a signpost system without turn detection. In this AVM system, the location of each monitored vehicle is stored and continuously updated in the vehicle. This position data is transmitted to the base station at intervals which are appropriate to the particular application. If a vehicle should become lost, a new position is automatically established at the next signpost without operator assistance.