Effective Measures to Restrict Vehicle Turning Movements

This study evaluated alternatives to raised/non-traversable medians on driveways and approaches. Raised medians are often considered as an effective technique to limit direct left-turns that may be due to a significant number of conflict points. The raised medians provide an added benefit of improved corridor aesthetics. This research effort specifically reviewed a variety of turn restriction alternatives to determine how effective they may be in addressing the safety and operational needs of the transportation network while still considering contextual sensitivities. The turn restrictions evaluated in this report are broadly separated into three categories: turn restrictions located only at the access point, turn restrictions located only in the roadway (typically some sort of median configuration), and combined turn restriction configurations. The literature review also identified the jug handle and roundabout design that could be considered to restrict turning maneuvers, but this research did not extend to these two infrastructure alternatives. The research team performed field evaluations in Oregon and Texas to determine the effectiveness of various turn restriction configurations. For the Oregon locations, the research team also evaluated recent crash histories to determine if turn restrictions were linked to observed crashes. In addition, the research team performed microsimulation evaluations to identify the operational impacts of the various turn maneuver restrictions. The full report is available online at http://www.oregon.gov/ODOT/TD/TP_RES/docs/Reports/2015/SPR766_RestrictVehicleTurningMovement_Final.pdf