Protected–Permissive Left-Turn Signal Control Mode: New Analytical Approach to Estimate Operational Benefit and Safety Cost

Abstract

Protected–permissive left-turn (PPLT) and protected only (PO) left-turn signal control modes have been widely used at signalized intersections. The selection between these two control modes is a complicated process in which practitioners need to consider safety and operational impacts. In this study researchers developed analytical models for estimating the operational benefits and the safety risks associated with the use of the PPLT control mode. Evaluation results demonstrated that the proposed models could provide accurate and reliable estimates for the delay reduction and the potential conflicts caused by the use of the PPLT mode. Results of this study will be useful for developing quantitative criteria for the selection between the PO and PPLT modes.

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