Most models for evaluating operating-speed consistency on two-lane rural highways estimate operating-speed profiles based on tangent length and degree of horizontal curvature. Some models also consider the effect of sight distance to horizontal curves. To add insight on the effects of these variables on safety and operations at horizontal curves, a base relationship between accident rates at horizontal curves and degree of curvature was established, and the effects of approach tangent length and approach sight distance on this relationship were examined. The results confirm that degree of curvature is a good predictor of accident rates on horizontal curves. Although the effects of approach tangent length and sight distance were not as clear, the results suggest that the adverse safety effects of long approach tangent length and short approach sight distance become more pronounced on sharp curves. (Author/publisher)
Abstract