This study involves the assessment of 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. However, many individual business owners have opposed the installation of raised medians due to fear of business loss. Recent Oregon focus on supporting economic development has raised awareness of the need for other effective ways to restrict vehicle turn movements that have less impact on businesses and freight movement. Consequently this research effort reviewed a wide 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 research summarized in this report reviews candidate turn restriction configurations that are presented in the literature or that are used by other transportation agencies. The turn restrictions 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 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 micro-simulation evaluations to identify the benefits of the various turn maneuver restrictions. Section 2.0 of this report provides background information regarding turning configuration options. This report chapter includes a literature review and a state of practice summary. Section 3.0 then summarizes the data collection and site selection aspects of the research effort. The analysis components of the study are then included in Section 4.0. The report concludes with Section 5.0 (Findings), Section 6.0 (References), and Section 7.0 (Appendix). Located in the appendix is a list of abbreviations and acronyms used in the report, detailed information on the Oregon and Texas study locations, and micro-simulation summary output information. (Author/publisher)
Abstract