Approach speeds at uncontrolled intersections with restricted sight distances.

Abstract

An unobtrusive study was made of vehicles approaching low-volume, uncontrolled cross-intersections, with restricted right sight distances, at which the give-way-to-the-right rule was operative. The hypotheses were that one factor that influenced motorists' approach speeds on the major road was the frequency with which vehicles emerged from the right and that most drivers exceeded the safe approach speed when this probability was low. The mean speeds at a lowand a high-probability intersection were 31 mph (SO km/h) and 22 mph (35 km/h), »s = 140 and 163, respectively (p < .01). (The maximum safe approach speed at each intersection was calculated to be 18 mph-29 km/h.) It was concluded that many drivers deliberately overrely on their predictions about the typical behavior of other drivers and that this is responsible for the behavior denned as hazardous. Further, it was hypothesized that when drivers exceeded the safe approach speed, they were relying on taking evasive action to avoid a vehicle that might emerge from the right. Reduced friction at the low-and high-probability intersections was accompanied by speed reductions of 3.0 mph (4.9 km/h) and 3.5 mph (S.6 km/h) and ns = 28 and 48, respectively (p < .01).This article is adapted from Cognition and Speed Control for Road Safety, an unpublished doctoral dissertation submitted by the author to the University of Melbourne, 1975. The financial support of The Sun News-Pictorial and the cooperation of the Road Safety and Traffic Authority is gratefully acknowledged. Appreciation is also expressed to colleagues for their advice on the investigation and the manuscript.Requests for reprints should be sent to S.