Radar, acoustic, and magnetic vehicle detectors

Three different physical phenomena are discussed as applied to the detection of roadway vehicular traffic. These detectors are the input data sources for vehicle-actuated traffic signal light control mechanisms, control systems, freeway surveillance, and statistical analysis. Radar detectors using microwave radio frequencies in the 2.5-10 MHz are discussed with regard to operating principles, design consideration, and practical application. Similarly, acoustical detectors operating in the 20-kHz range and low-flux density change magnetic detectors are discussed. A comparative analysis is made of radar, acoustical, and magnetic detectors, as well as mechanical, magnetic, induction, and optical detectors.