Coordinated Optimization of Signal Timings for Intersection Approach with Presignals

Abstract

Many congested intersections have heavy traffic volume on movements for which there is insufficient capacity because of geometric limitations. Installing presignals at midblock locations and reorganizing traffic upstream of the approach of an intersection combine to be a promising and cost-effective method for addressing these capacity limitations. A coordinated optimization model was developed for an isolated intersection approach with presignals to increase the protected left-turn phase capacity. The presignal model was based on two principles: (a) explicitly capture the interaction between the presignal and the main signal by modeling the queuing process and capacity constraints of temporal and spatial limitations of the intersection and (b) optimize the signal timings of both the presignal and the main signal as well as the offset between them to produce the best operational strategy for the approach. The minimum green time required and the delay-minimization problems are considered. Extensive experimental analysis has shown that the presignal model outperforms the conventional control method (without presignal). Sensitivity analysis of the signal timing method that will assist traffic engineers with selecting the appropriate length of the sorting area, phase sequence, and early starting time of presignals was conducted. The results from the study offer a basis for traffic practitioners, researchers, and authorities on which to design and utilize presignals in locations where there is a need to increase intersection capacity for congested movements.