Two-stage model for optimizing traffic signal control plans of signalized Superstreet

Despite the increasing implementations of Superstreets, a reliable method to design their signal plan remains unavailable. To account for the unique geometric features of Superstreets, this study presents a two-stage signal optimization method where the first stage determines the optimal signal plan for each sub-intersection and the second stage optimizes the offset for signal coordination. Implementing the Mixed-Integer-Linear-Programming (MILP) technique for the model formulation, the first stage has the objective of maximizing total traffic throughput and the second stage aims to maximize the bandwidths and minimize the delay experienced by the minor road drivers. To assess the proposed model's effectiveness, the study further conducts signal performance evaluations using simulation calibrated with field data collected in Maryland. The results of extensive experiment tests reveal that the proposed model can effectively offer signal progressions to both heavy through and left-turn movements, and prevent the potential queue spillback among a Superstreet's four closely-spaced sub-intersections.