Left-turn Phasing Decisions Based on Conflict Analysis

The need to balance safety and operational efficiency at intersections requires special attention for accommodating left turn movements. Signalized intersections epitomise this need because unnecessary protection of left turns can significantly increase operational delay. Left turn protection however, increases safety and there is a need for proper balancing between the conflicting goals of safety and operations. The long time required to collect crash data to evaluate the use of existing warrants render them frequently ineffective and the need for a preliminary design tool to assist in left turn phasing decisions is needed. This research developed a quantitative safety assessment tool that predicts left turn related conflicts and uses them to determine the appropriate phasing scheme for left turns. The model was developed based on VISSIM micro-simulation software in conjunction with the Surrogate Safety Assessment Model.