Citation

Powers LD, Michael HL. Highw. Res. Board bull. 1961; 303: 10-24.

Copyright

(Copyright © 1961, National Research Council (U.S.A.), Highway Research Board)

DOI

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PMID

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Abstract

This paper reports the results of a study at three distinctive locations of the combined effect of various forms of delineation on driver speed patterns and on accidents. The locations concerned were a narrow bridge, a hazardous intersection, and an adequate intersection, all in rural areas. The various forms of delineation under consideration were roadside reflectors, pavement edge lines, signing, and, in one case, channelizing islands. Only free- moving passenger cars traveling on dry pavement under optimum day or night visibility conditions were considered in the speed study. In the case of one location heavy commercial vehicles were also recorded, however, speed patterns for cars and trucks were analyzed separately. Spot speeds were recorded, using electro-matic radar speedmeters, at various points at each location during the day, at night, and again at night after the additional delineation had been installed. From 30 (for heavy trucks) to 300 or more observations, depending on the estimated variability of the speeds and prevailing traffic volumes, were made for each movement. Accidents were also analyzed for a like period before and after placing the delineation, with proper delineation maintained during the after period. The results were variable, but indicated a slight increase in speed and a slight reduction in accidents after the delineation.