Safety Effectiveness of Unsignalized Restricted Crossing U-Turn Intersections in Mississippi using an Empirical Bayes Before–After Study

Abstract

At-grade intersections on rural high-speed highways can be hazardous, particularly where lower-speed vehicles from minor roads must cross high-speed traffic on major roads. To enhance safety at these junctions, an alternative design known as restricted crossing U-turn (RCUT) has gained considerable interest in recent years. RCUTs can help reduce both the number and severity of crashes by rerouting minor road traffic to downstream U-turns, thereby minimizing crossing conflict points between high-speed and low-speed vehicles. This research aimed to estimate the safety performance following the implementation of eight unsignalized RCUT intersections on rural high-speed highways in Mississippi. The study considered two different definitions of the intersection influence area and employed two distinct methodologies: naïve average annual number of crashes analysis, and a rigorous Empirical Bayes (EB) method. To facilitate the crash modification factor (CMF) development, new local safety performance functions (SPFs) were developed, and the results were compared with those derived from the HSM (Highway Safety Manual) SPFs and state-specific SPFs. Results showed significant crash reductions following RCUT implementation: a 63% reduction in total crashes and a 79% reduction in fatal and injury crashes. Annual angle crashes dropped by over 96%, and left-turn crashes by 40%, although sideswipe and rear-end crashes increased slightly as a result of redirected traffic. Despite methodological differences, all analyses confirmed RCUTs’ effectiveness in improving safety, making them a promising solution for high-speed rural intersections in Mississippi.