Citation

Cleveland DE, Kostyniuk LP, Waissi GR, Olson PL, Fancher PS. Transp. Res. Rec. 1985; 1026: 13-23.

Copyright

(Copyright © 1985, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

A review of stopping sight distance parameters has recently been completed for NCHRP. AASHTO currently recommends a driver perception-response time of 2.5 sec, and this value was found to be satisfactory. AASHTO currently uses braking distances based on locked-wheel skidding on poor-condition wet pavement surfaces. It was concluded that this is not appropriate for speeds above 30 mph if a vehicle with minimum legal tire tread is to be stopped in its own lane on a wet pavement of this type. For a vehicle to be able to make such a stop, it was concluded that braking distances should be increased. At a speed of 40 mph, the distance increases to 360 ft and, at 80 mph, it increases to 1630 ft. Examination of recently measured speed distributions showed that drivers continue to select the same speeds on wet pavements as they do on dry roads and that the AASHTO policy of using the same initial speed for both wet and dry conditions should be retained. Lowering the driver eye height to 40 in. from the current AASHTO value of 42 in. would accommodate more than 95 percent of the automobile driver-vehicle combinations expected to be in use late in this decade. Such a change was recommended because a 42 in. eye height would not accommodate 25 percent of the vehicles. No research on the appropriate height of the object was performed. Ten vertical curve locations at which there was less than AASHTO policy minimum available stopping sight distance were found to have an average of about 40 percent more accidents than nearby locations with adequate sight distance. Several horizontal- and vertical-curve geometric design aids based on derivations made in the research are presented.

Language: en

Keywords

HIGHWAY SYSTEMS; TRANSPORTATION - Accident Prevention; AUTOMOBILE DRIVERS - Research