Citation

Baker JS. Highw. Res. Board bull. 1954; 91: 33-38.

Copyright

(Copyright © 1954, National Research Council (U.S.A.), Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

As a deterrent to people who would otherwise drive faster than the law permits, police activity on the highway is believed to work in three ways: (1) the visible presence of a patrol unit presents the immediate possibility of enforcement against violators at that time and place, (2) the general belief that speed laws are enforced on a highway will deter drivers from exceeding the legal speed limits, even if no patrol unit is known to be in the vicinity, (3) a general belief that traffic laws are enforced in a community or other area will stimulate compliance with the speed laws in that community. Pilot studies have been made at the traffic institute, northwestern university, in a cooperative project with the bureau of public roads to explore questions raised by the first and third effects of enforcement on speeds mentioned above. Various methods of measuring the speeds of vehicles were studied, and it was found that two types of recording speed meters were suitable. Of six different means of describing speed considered, it was decided that the most practical for the purpose of the study is the average excess speed, which is the sum of the amount by which each vehicle exceeds the speed limit divided by the total number of vehicles. Studies were made of the effects on average excess speed of both a standing patrol unit and a moving patrol unit for traffic within limited distances from the unit. Studies also were made of vehicle speeds in chicago before and after a substantial increase in the level of law enforcement.