Transit Signal Priority Method Based on Speed Guidance and Coordination Among Consecutive Intersections

Abstract

Speed and punctuality are essential to the quality of bus services. To reduce bus delays and increase bus speed, a transit signal priority (TSP) method based on speed guidance and coordination among consecutive intersections is proposed. The TSP problem is formulated as a binary mixed integer nonlinear program. Impacts of TSP on the current intersection and adjacent intersection downstream are measured by deviations of split time from background timing plans and non-overlapping degrees, respectively. The weighted sum of the two measurements and bus travel time is taken as the objective function. The method does not change the original cycle length, and it is adaptive to timing plans with an arbitrary number of phases. Exclusive bus lanes are required to provide good conditions for speed guidance. A simulation case study of three consecutive intersections in Shanghai, China, is conducted. In the experiments, no priority method, the conventional TSP method, and the proposed method are applied. The results indicate that the proposed method performs the best. Compared to no priority method, the average travel time of buses, delays of bus, and delay per capita are reduced by 26.3%, 91.3%, and 14.5%, respectively. In addition, no serious deterioration is observed in the experience of other road users as the congestion level rises. The study illustrates the possibility of giving high priority to buses without significant negative impacts on other road users, and it can help traffic managers to alleviate traffic congestion in densely populated cities.