NCJ Number
83012
Date Published
1982
Length
67 pages
Annotation
The technology of police traffic radar and the rudiments of its operation are explained, primarily for the benefit of police officers and lawyers.
Abstract
The history of radar is traced from its prominent use in World War II to measure the distance and direction of enemy ships and planes to its first use in traffic management in 1948, followed by a discussion of developments in its use as a vehicle speed measurement device through 1981. The basic principles of radar are explained under the topics of wavelength, frequency, and shift; Doppler effect and shift; the radar beam; use of the antenna and range selection; the cosine angle effect; moving radar; and detection and jamming devices. Knowledge of these fundamental concepts is considered necessary for the radar operator to be competent and effective. The discussion of general operating procedures deals with preparation for use, installation, calibration checks, operating adjustments, site selection, valid target reading, and care of the unit. Attention is also given to interference, a man-made or natural condition that will have an altering effect on either a transmitted or reflected signal, and radar anomalies, deviations that could cause an improper speed reading. Judicial decisions which have marked the development of the treatment of the use of radar in vehicle-speed trial cases are outlined. Guidelines needed for a prima facie presumption of radar accuracy sufficient to support a speeding conviction are presented. Questions that might be put to an officer by a defense attorney to ascertain the officer's training and experience in the use of radar are presented. Calculations involved in the use of radar for speed determination are appended, and a bibliography with 15 listings is provided, along with a subject index.