Effects of Approach Speed at Rural High-Speed Intersections

Speed can increase the risk of injury-producing crashes, especially at intersections where vehicles may be approaching and entering the intersection with high speed differentials. It is known that roundabouts force all drivers to reduce their speed in the intersection; however, speed data in advance of the roundabout approach were not available for roundabouts with high-speed approaches to verify this phenomenon. In this research, a comparative evaluation of the difference in the average approach speeds between rural roundabouts and rural two-way-stop-controlled intersections and between rural roundabouts with and without rumble strips on the intersection approaches was performed. Approach speed data proved that drivers could slow down in advance of roundabouts on rural roadways. The mean speed 100 ft from the yield line of the roundabouts was 2.5 mph lower than the mean speed 100 ft from the stop bar at stop-controlled approaches. Additionally, a comparison of roundabout approaches with and without rumble strips showed mean speeds 4.3 and 3.3 mph lower 100 and 250 ft from the yield line, respectively, for approaches with rumble strips; however, the variation in speeds increased with the introduction of rumble strips.