Study Details

Study Title: Safety Impacts of Directional Median Openings at Downstream U-Turn Locations

Authors: Qi et al.

Publication Date: JAN, 2016

Abstract: Over the past decades, many states and local transportation agencies have installed directional median openings on urban divided roadways to help avoid potential conflicts. At directional median openings, left-turn movements from driveways or minor streets have to make an alternative movement, i.e., a right-turn followed by a U-turn, which would increase the U-turn demands at the downstream openings and may increase the crash risk at the U-turn locations. Therefore, the objective of this study was to investigate the safety impacts of directional median openings at downstream U-turn locations. For this purpose, a Poisson regression model was developed to analyze the factors that contributed to the crashes that occurred at the downstream U-turn locations of directional median openings. The results showed that 1) higher downstream U-turn volume and left-turn volume resulted in more crashes at downstream U-turn locations and 2) the closer the downstream U-turn location was to the subject opening, the more crashes that occurred at the downstream U-turn location. These findings indicated that the selection of U-turn locations is critical for the safety performance of directional openings because converting a full median opening to a directional median opening generates more U-turns at downstream openings. Diverted left-turn traffic should not be allowed to make U-turns at a closely-spaced opening that already has significant U-turn or left-turn volumes

Study Citation: Qi, Y., Y. Wang, X. Chen, and G. Liu. "Safety Impacts of Directional Median Openings at Downstream U-Turn Locations". Presented at the 95th Annual Meeting of the Transportation Research Board, Paper No. 16-6761, Washington, D.C., (2016).


CMFs Associated With This Study

Category: Alignment

Countermeasure: Install directional median openings at downstream U-turn locations

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
CMF Equation 3 Stars All All Principal Arterial Other Freeways and Expressways Not specified