Left turn phasing type determination at isolated intersections solved by a genetic algorithm

A left turn could be treated as a permitted or protected left turn. Good left turn treatment could improve the efficiency at intersections. This paper aims to solve the left turn phasing type problem with the goal of minimizing the total delay. The determination of left turn phasing types extends the lane-based signal optimization method by introducing the decision variables of left turn phasing type indicators. This problem is solved with a genetic algorithm with penalty functions. It is found that permitted left turns contribute to total delay reduction.