This paper develops an ultrasonic vehicle detector (UVD) system that can be implemented in a side-fire configuration and presents extensive experimental results. Conventionally, UVD systems are installed using overhanging structures or bridges in overhead configurations. In this overhead configuration, the sensors are mounted directly over the road surface. If these sensors can be mounted from the side of a road, the installation cost can be reduced. In addition, the aesthetic integrity of roadways will not be affected very much. However, this side-fire configuration has not been used, because of the fact that vehicles generally do not have sufficiently large oblique-angled surfaces to reflect the emitted ultrasonic wave back to the sensor for detection. This paper reports on the feasibility of a side-fire UVD system. A new low-cost instrumentation and control system for side-fire implementation was developed, and comprehensive experiments were performed at highway and downtown test sites. Experimental conditions included various traffic conditions as well as various weather conditions, including daylight, dusk, night, heavy rain, and heavy snow. Traffic data were generated for every 5 minutes. For the highway location, the vehicle counting error was less than 1%. For the downtown location, the error was approximately 3% during normal weather conditions and approximately 5% during a snow storm. The larger error in downtown is mainly attributed to vehicles changing lane. For the covering abstract see ITRD E114174.
Abstract