A Systematic Literature Review Exploring Safety of U-Turns at Uncontrolled Median Openings

Abstract

U-turning safety at uncontrolled median openings (UMOs) has been compromised because of critical vehicular interaction and driving behavior. This safety study focuses extensively on U-turning vehicles at UMOs as a result of their complex U-turning maneuvers, which provide a significant risk of severe collisions. Several attributes that affect U-turning safety are identified by conducting this systematic literature review. The various safety attributes affecting U-turn safety, namely geometrical, operational, crash-related, and surrogate measures, have been examined across the selected studies. The results indicate that 46.15% of the studies identified operational factors as primary contributors, 20% attributed this to geometrical attributes, 18.46% to crash-related attributes, and 15.38% to surrogate measures. These attributes were analyzed through a Preferred Reporting Items for Systematic Reviews and Meta-Analyses-based systematic review to determine significant risk factors, potential safety improvement techniques, literature gaps, and limitations in U-turn safety. This intensive study identified the impact of different safety contributing factors, providing significant insight into designing and planning safer U-turning operations at UMOs. The study will also be helpful in suggesting some geometric design argumentation schemes and identifying relevant safety indicators that transport professionals and policymakers need to implement or modify to establish safe U-turning operations through UMOs on urban, suburban, and rural roadways. Furthermore, the analysis of historical accident data yields additional safety criteria that suggest surrogate safety measures to aid in determining the likelihood and severity of collisions in U-turn operations before an actual collision. The systematic review’s findings have both practical and theoretical implications, including significant recommendations on effective geometrical, operational, and surrogate measures. To achieve complete safety improvements, future research must dive further into the complexities of driver behavior and awareness, collision severity, and additional operational attributes.