A Framework for Developing Left-Turn Operations Guidelines at Signalized Intersections

The State of Texas in the United States deploys protected/permissive left-turn control at selected intersections throughout the state to avoid unnecessary delays for left-turning vehicles at these intersections. The choice between protected only and protected/permissive left-turn controls depends on how traffic operations engineers balance operational efficiency and safety at a particular intersection. When protected/permissive left-turn control is used at an intersection, there are a variety of left-turn signal phasing schemes to use. While motorists are generally in favor of having protected/permissive left-turn control, the traffic engineering community has been concerned with the overall safety of deploying protected/permissive left-turn control at some intersections. Despite decades of research, there are no widely accepted guidelines for engineers to choose between protected only and protected/permissive left-turn controls. In addition, there exist no uniform guidelines about the selection of the most appropriate left-turn phasing schemes for a given intersection in Texas. Policy and practices about left-turn operations vary from one region to another in Texas. Furthermore, within regions with multiple jurisdictions, different practices exist from one jurisdiction to another. This lack of consistency is confusing to drivers and may result in a greater number of crashes related to left-turn operations. After a thorough review of related work, this study presents a framework for developing left-turn operations guidelines at signalized intersections in Texas.