Citation

Wilson JE. Traffic Eng. Inst. Traffic Eng 1965; 35(11): 12-14, 44.

Copyright

(Copyright © 1965)

DOI

unavailable

PMID

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Abstract

Various means of giving advance warning to drivers of motor vehicles, and the need for greater alertness and caution in driving during periods of reduced visibility are being studied. The purpose of the study is to find means of preventing, the multiple vehicle accidents associated with reduced visibility. All the following conclusions (except the first) are for daylight conditions and low to moderate traffic volumes (0 to 1000 vehicles per lane per hour). The findings are based on a very limited set of conditions, and generalizations should not be made from the following few and tentative findings: 1) no instrument is available to measure the distance a driver can see; 2) the fog by itself causes a small reduction in speeds; 3) at fog visibilities of 200 feet or less, posted speeds reduce vehicle speeds approximately another 5 mph for both low traffic volumes and moderately high volumes; 4) regardless of the speed posted and/or the safe speed for the distance visible, evidently the average driver will not drive below 38 to 40 mph in a free traffic flowing condition and with visibility limited to 100 to 200 feet; 5) posted speeds cause some better grouping of the speeds about the mean; 6) at low volumes, headways are not affected by fog; 7) at moderately high volumes, fog reduced visibility does decrease the number of vehicles traveling at short headways (1.0 to 2.0 seconds); and 8) with posted speed limits and limited visibility, the percentage of the very short tailgating headways are reduced.

KEYWORDS: Alertness; Drivers; Fog; Headways; Multiple vehicle crashes; Prevention; Reaction time; Speed; Speed limits; Traffic flow; Traffic volume; Visibility; Warning systems; Close following

Language: en