A single element piezoelectric sensor for vehicle classification using the ratio of track width to length

Abstract

Accurate vehicle count and classification reporting is a principal application of intelligent transportation system. United States Departments of Transportation (DOTs) use this information to design safe, suitable roadways. A wide variety of classification systems are currently employed. Regardless of type, an optimal system must be cost effective, require minimal maintenance, cause limited pavement damage during installation, and provide accurate information. Currently, the most widely used systems combine inductive loops and piezoelectric sensors. Most cause severe pavement damage during installation and fail to provide accurate classification for a variety of classes-class 1 motorcycles in particular. This paper introduces a vehicle classification system that employs a single element piezoelectric sensor placed diagonally across a traffic lane. The system is able to accurately classify 13 Federal Highway Administration vehicle classes, including class 1 motorcycles. The novel classification method utilizes the ratio of vehicle track width-to-length (w/l) as well as a traditional axle-spacing scheme to classify vehicles. The single-element system is cost effective and reduces pavement damage primarily because it utilizes only a single sensor. Two highway test deployments found the system capable of achieving classification accuracy of up to 98.8% when employing the (w/l) method and 84.4% when employing the axle-spacing method.