The National Academies

NCHRP 17-108 [Active]

Developing Crash Modification Factors for Alternative Intersections

  Project Data
Funds: $600,000
Staff Responsibility: David M. Jared
Research Agency: University of North Carolina -- Chapel Hill
Principal Investigator: Taha Saleem
Effective Date: 8/25/2022
Completion Date: 8/25/2025



Alternative intersection designs, including the Displaced Left Turn (DLT), Median U-Turn (MUT), and Restricted Crossing U-Turn (RCUT), have been implemented nationwide to reduce congestion, crash frequency, and crash severity. The reduced number of traffic signal phases and conflict points at these intersections can improve traffic operations and safety. Much research has been conducted to develop safety performance functions (SPFs) and crash modification factors (CMFs) for various intersection designs and control types as well as conversions of traditional intersections to other forms including roundabouts. Other studies have been conducted to evaluate the safety benefits of different intersection designs.


The use of alternative intersections in the United States has increased substantially in recent years, including combinations of alternative intersection elements at different approaches to the same intersection. The operational benefits of alternative intersections compared with conventional intersections are well established. The reduced number of conflict points for alternative intersections has demonstrated 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 DLTs are also supported by intersection data following DLT installation; however, potential safety concerns have been expressed, especially for older drivers and those unfamiliar with alternative intersections.


Research is needed to develop quantitative safety analysis methodologies for certain types of alternative intersections that are not currently available in resources such as the AASHTO Highway Safety Manual and CMF Clearinghouse. The research would inform transportation agencies, industry, and the public of the safety benefits of alternative intersections by quantifying the predicted reduction in crash frequency and severity resulting from conversion of conventional intersections to DLT, MUT, RCUT, or other alternative intersections. Ultimately, it would help transportation professionals evaluate alternative intersection strategies in terms of safety benefits and support progress towards Vision Zero goals across the United States.





The objectives of this research are the following: 


1. Determine the current knowledge and research gaps in quantitative crash prediction methodologies for alternative intersections, which include but are not limited to DLT, MUT, and RCUT.


2. Develop, modify, and statistically validate crash predictive methodologies such as SPFs, CMFs, and crash severity distributions to quantify the safety effects of these alternative intersections.


3. Where development of quantitative methodologies may not be possible, identify risk factors, proxies, or surrogates for vulnerable road users consistent with these methodologies.



STATUS: Research in progress.


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