Operational Comparison of Transit Signal Priority Strategies

Priority strategies for bus transit are implemented with the purpose of expediting transit flow by reducing travel times and delay while providing a more reliable system that may attract new riders and increase transit capacity. Such strategies are a critical component of bus rapid transit, although the strategies can also be applied to regular local bus operations. The interference of general traffic when buses are operating in mixed traffic results in a reduction in speed and capacity. Intersection priority treatments reduce signal delay and result in travel time savings to transit. Transit signal priority (TSP) strategies may be applied across several intersections, depending on the level of service and lane configuration characteristics of the signalized intersections along a corridor, and can be combined in the same signal operation for each approach serving transit. This paper presents a methodology for evaluating the impacts of TSP treatments on transit operations at a specific intersection by comparing various treatment options. The effectiveness of the transit priority treatment was measured by the travel time savings for bus operations given in minutes of reduced delay. The applicability of this methodology in the planning of TSP strategies for transit service is explained in two sample calculations, and the results are compared to determine the feasibility of the TSP treatment that would give the highest travel time savings for signalized intersections along the study corridor.