Evaluating The Effects Of Prohibiting Left Turns And The Resulting U Turn Movement

Evaluating the Effects of Prohibiting Left Turns and the Resulting U-turn Movement

The objective of this research was to evaluate the operational and safety effects of restricting direct left turns from a driveway and providing alternatives to accommodate the left turn deterred traffic. This study was conducted in three phases: survey of state agencies, operational analysis, and safety assessment. Very little operational difference was found between no restrictions on direct left turns versus the restrictions with the U-turn alternative movements from site to site. While changes in the traffic volumes on the mainline had an impact in specific instances, no definite trends were apparent. As a result of all findings in this study, it is proposed that alternatives must be evaluated on a site-by-site basis. This study also found the jughandle design to be a superior alternative for accommodating left-turn deterred traffic for multi-lane divided and undivided sites compared to mid-block or intersection U-turns. The safety assessment revealed that a right turn followed by a U-turn movement is safer than the direct left turn.

Geometric Design and the Effects on Traffic Operations, 2005

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