Abstract: To optimally allocate the time and space resources for two adjacent intersections with coordinated signals and short left-turn lanes on the common section of a road, an optimization model was presented to jointly obtain the signal cycle length and green slit for each intersection. The objectives are to maximize the passing capacity of the entire intersection and minimize the total delay of vehicles. The decision variables of the model are the length of each short left-turn lane and the effective green time per phase. A case was designed to verify the effectiveness of the proposed model. First, two signal timing plans for each intersection were obtained using the proposed model and Webster model, respectively. Then, the offset between coordinated phases was calculated by a known method. Finally, the traffic operations under the two signal timing scenarios were simulated using VISSIM software. The outcomes show that the unit delay is decreased by 30% and the vehicle throughput is slightly increased for each intersection under the optimization scenario.

Key words: engineering of communications and transportation system, short left-turn lanes, coordinated signals, capacity, unit delay