Citation

Zador P, Stein H, Shapiro S, Tarnoff P. Transp. Res. Rec. 1985; 1010: 1-8.

Copyright

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

DOI

unavailable

PMID

unavailable

Abstract

The relationship of the timing of traffic signal clearance intervals (yellow phase plus red light in all directions) to traffic flow and crash rates at signalized intersections was examined. Specially designed traffic data-logging devices provided information on the presence and speed of vehicles and the signal timing for 91 signalized intersections throughout the United States.

RESULTS showed that intersections with more adequate clearance intervals had substantially fewer rear-end and right-angle crashes than those with less adequate clearance intervals. The observed flow of traffic through the intersections after the onset of yellow was largely unaffected by variation in the lengths of clearance intervals; thus the proportion of drivers exposed to cross-street traffic decreased as the clearance interval lengths increased. Ideally, clearance intervals should be long enough to allow slower traffic approaching the intersection to cross before the cross-street traffic starts. However, for the intersections examined in this study, the group with the highest average crash rate also had the slowest average crossing speed, the widest cross streets, and the shortest and least adequate clearance intervals. Crash increases associated with deficient clearance intervals may be caused by abrupt stops by drivers who are reluctant to traverse wide cross streets with traffic waiting to start up or by vehicles unable to clear the intersection under cross-street red-light protection.

Record URL:
http://onlinepubs.trb.org/Onlinepubs/trr/1985/1010/1010-001.pdf

Language: en

Keywords

ROADS AND STREETS - Intersections; STREET TRAFFIC CONTROL; TRAFFIC SIGNS, SIGNALS AND MARKINGS - Efficiency