Alternative intersection designs, including Displaced Left Turn (DLT), Median U-Turn (MUT), and Restricted Crossing U-Turn (RCUT), have been implemented in the United States to reduce congestion. The reduction in the number of traffic signal phases and conflict points at these intersections results in improved traffic operations and safety. Various research has been conducted to develop crash modification factors (CMFs) for typical intersections as well as conversion of traditional intersections to roundabouts. Additional studies have been conducted to evaluate the safety benefit of different intersection configurations.
In the past 10 years, the number alternative intersections have increased substantially in the U.S. The operational improvements of the alternative intersections over conventional intersections have been proven. The total number of conflict points for alternative intersections are lower than traditional intersections, and, as a result, offer safety advantages over conventional intersections. Studies show significantly lower crash rates with MUTs and RCUTs for both corridor-wide and intersection related data. Lower crash rates for DLT’s are also supported by intersection data following DLT installation; however, there are safety concerns, especially for older drivers and those unfamiliar with alternative intersections.
The objective of this research is to develop CMFs for alternative intersection types, to include but not be limited to DLT, MUT, and RCUT configurations, and hence a tool for estimating crashes with and without alternative intersections. The research would inform engineers, transportation agencies, and the public of the safety benefits of alternative intersections by quantifying the reduction in crash frequency and severity resulting from conversion of traditional signalized intersections to DLT, MUT, RCUT, or other alternative configuration. Ultimately, it would help transportation professionals evaluate alternative intersection strategies in terms of safety benefits. The estimation/evaluation tool could be included in Highway Safety Manual, state DOT manuals and guidelines, and in the CMF Clearinghouse, and it could support progress towards Vision Zero goals across the U.S.
Direction from the AASHTO Special Committee on Research & Innovation: The scope of work should focus on Safety Performance Functions before CMFs, and coordinate with active, related NCHRP research. The results should be applicable across the country, although these intersections may not yet be widely used. Additional intersection types may be of interest in addition to those listed.