Field Testing and Evaluation of a Wireless-Based Transit Signal Priority System
Chen-Fu Liao, Gary A Davis
Report no. CTS 11-25
Most signal priority strategies implemented in various U.S. cities used sensors to detect buses at a fixed or preset distance away from an intersection. Traditional presence detection systems, ideally designed for emergency vehicles, usually send a signal priority request after a preprogrammed time offset as soon as transit vehicles are detected without the consideration of bus readiness. As part of the Urban Partnership Agreement, Metro Transit, Minnesota Department of Transportation (MnDOT), and the City of Minneapolis have implemented Transit Signal Priority (TSP) along Central Avenue from north Minneapolis (2nd Street SE) to south of I-694 (53rd Avenue NE) with total of 27 intersections. Transit performance before and after the deployment of a TSP strategy was examined through the data analysis process to evaluate the effectiveness and benefit of a TSP strategy. The objective of this study is to deploy and validate a wireless-based TSP strategy developed from earlier studies by considering bus schedule adherence, location and speed. A TSP onboard system using embedded computer was developed to interface with EMTRAC radio modules to bypass the EMTRAC TSP algorithm on current buses. Field experiments were performed by installing University of Minnesota (UMN) TSP units on four RTE10 buses for two weeks. The EMTRAC algorithm was temporary disabled on the test vehicles. Link travel time and node dwell time on the TSP-equipped route segments are compared. The results indicated the UMN TSP algorithm gain additional 3-6% of travel time reduction as compared to other RTE10 buses operating during the two-week test period.