Citation

Dart OK. Transp. Res. Rec. 1977; 643: 23-32.

Copyright

(Copyright © 1977, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

There have been many studies of the effect of the 88.5-km/h (55-mph) speed limit on vehicle speeds and accidents. Although several of these studies mention the need for enforcement to make the speed limit more effective, most do not present any enforcement data. This paper focuses on data from North Carolina, Mississippi, and Louisiana to show the probable role of enforcement. Time-series plots of speed, volume, and accident data for North Carolina are given for the period of 1973 and 1974. Time-series graphs of enforcement data for North Carolina, Mississippi, and Louisiana and Louisiana speed, volume, and accident data have been developed from the published quarterly and annual reports of the state police and highway agencies. The initial decrease in speeds caused by the energy crisis in the three states has been eroded in the past 2 years; except for Interstate highways, speeds have returned to precrisis levels. Of particular importance, however, are that speeds are now more uniform (standard deviations are lower and pace-group percentages have increased) and very few vehicles are exceeding 105 km/h (65 mph). There are strong indications that the increased enforcement levels of 1974 to 1976 are responsible for maintaining the more uniform and safer speed levels. Louisiana data for 1974 and 1975, as compared with data for 1971 and 1972, show not only significantly fewer fatalities on the rural highways, but also large reductions in the percentages of all rural accidents and of rural fatal accidents for which excessive speed was cited as a contributing factor. A more detailed study of enforcement versus accident rate is said to be warranted.