Left turn guidance based on crossing conflict analysis

Left turn movements at an intersection are considered the most critical due to their implications on safety and operational performance. This is more critical for signalized intersections due to the need for balancing operational efficiency with safety. Signal phasing schemes are implemented to control such movements and improve the safety of the intersection. However, providing the left turn movement with its own phase often reduces the intersection operational efficiency. Warrants have been developed to decide between phasing schemes, but those involving safety require years of study to evaluate. There is a need for a preliminary design tool to assist in left turn phasing decisions. The research proposes a quantitative safety assessment tool that predicts left turn related conflicts as the deciding measure between different phasing schemes. VISSIM micro-simulation software in conjunction with the Surrogate Safety Assessment Model were used to develop the model.