Compact vehicle sensor using a retroreflective optical scanner

A compact vehicle detection and separation sensor that employs an optical scanner and retroreflective optical system has been proposed and developed for the first time for toll gate systems. The compact size of 150 mm/spl times/130 mm/spl times/200 mm allows easy installation and the tidy appearance of the gate. The sensor that repetitively scans pulse modulated and rectangularly shaped LED light successfully distinguishes between a tailgating vehicle which closes to 300 mm tail to nose at 60 km/h and a vehicle with a trailer jointed with a /spl phi/ 50 mm pole.