Effective Measures to Restrict Vehicle Turning Movements

This study evaluated alternatives to raised and nontraversable medians on driveways and approaches. Raised medians are often effective for limiting direct left turns at significant conflict points. Raised medians also improve corridor aesthetics. This research reviewed a variety of turn restrictions to determine how effectively they address the operational needs of the transportation network while addressing contextual sensitivities. The turn restrictions evaluated in the study were separated into three broad categories: turn restrictions located only at the access point, turn restrictions located only in the roadway (typically some type of median configuration), and combined turn restriction configurations. Field evaluations in Oregon and Texas were performed to determine the effectiveness of various turn restriction configurations. In addition, microsimulation evaluations were used to identify the operational impacts of the various turn maneuver restrictions.