This article reviews the development and operation of two sensors, using highly accurate and reliable laser-based detection and classification technologies. These sensors are among the laser sensors, developed by Schwarz Electro-Optics (SEO), which (1) measure vehicle speeds; (2) count and classify vehicles; and (3) measure other traffic parameters, such as density, flow rate, and queue length. To estimate speed, two fixed or scanning beams are used, one angled slightly forward along the road, and the other slightly backward. Autosense I is a detector of vehicle presence, height, and speed, using fixed beams. It is mounted over a road, and uses two diverging fan-shaped laser beams towards the road surface. For remote site operation, it has been adapted to operate from batteries and a solar panel. It also uses a spread-spectrum radio link to transmit traffic data. Autosense II is an integrated vehicle detection and classification unit, using scanning beams and a laser-generated three-dimensional vehicle profile. Tests confirmed 100% detection accuracy in fair weather and 95.5% classification accuracy for eight vehicle classes; this accuracy is expected to improve as the classification algorithm is developed further. Autosense I and II systems have begun to be installed in North American toll road systems.
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