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 low-and a high-probability intersection were 31 mph (50km/h) and 22 mph (35km/h), ns-140 and 163, respectively (p less than .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 in their predictions about the typical behaviour of other drivers and that this is responsible for the behaviour defined 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 (5.6 km/h) and ns-28 and 48, respectively (p less than .01). /Author/