Design of LRT Signal Priority to Improve Arterial Traffic Mobility

Transit signal priority (TSP) is a cost-effective strategy for improving the movement of public transit vehicles, such as Light Rail Transit (LRT), buses, and streetcars, through controlled intersections. The application of TSP strategies improves the reliability and quality of service for transit vehicles with less disruption to normal traffic. The City of Edmonton in Alberta, Canada has recently extended its LRT system, which mainly runs through at-grade intersections. Edmonton’s LRT is currently operating under pre-emption, which causes significant delays to other traffic. The problem is especially pronounced during peak hours when the LRT headway is decreased to 5 min in both directions. This has led to dissatisfaction among motorists using the roadway along the LRT corridor. This paper analyzes different TSP strategies for improving the performance of the LRT corridor. A standard microsimulation tool with a ring barrier controller emulator was used to implement the strategies at a major intersection during peak hours. Field data for both morning and evening peak hours were collected at four intersections along the LRT corridor for the calibration of the model. Three strategies were explored in this paper: (1) simple LRT pre-emption, (2) LRT prediction and pre-emption, and (3) LRT prediction and pre-emption together with transit bus priority. A number of performance measures were used to evaluate each strategy. Results revealed that Strategy 2, where LRT arrival time is predicted to provide LRT pre-emption, yields the highest improvement in corridor performance.