Bus Signal Priority on GPS and Wireless Communications - Phase II
Principal Investigator(s):Gary Davis, Professor, Civil, Environmental and Geo-Engineering
- Chen-Fu Liao, Researcher, Mechanical Engineering
Providing signal priority for buses has been proposed as an inexpensive way to improve transit efficiency and productivity and to reduce operation costs. Bus signal priority has been implemented in several U.S. cities to improve schedule adherence, reduce transit operation costs, and improve customer ride quality. Current signal priority strategies implemented in various U.S. cities mostly utilize 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 signal priority request after a preprogrammed time offset as soon as transit vehicles are detected without the consideration of bus readiness.
The objective of this study is to take advantage of the already equipped GPS/AVL system on the buses in Minneapolis and develop an adaptive signal priority strategy that could consider bus schedule adherence, number of passengers, location, and speed. Buses can communicate with intersection signal controllers using wireless technology to request signal priority. Communication with the roadside unit (e.g., traffic controller) for signal priority can be established using the readily available 802.11x WLAN or the DSRC (Dedicated Short Range Communication) 802.11p protocol currently under development for wireless access to and from the vehicular environment.
This work is exploring proposed priority logic and its evaluation using microscopic traffic simulation. Simulation results indicate that a 12%-15% reduction in bus travel time during morning peak hours (7 a.m.-9 p.m.) and 4%-11% reduction during afternoon peak hours (4 p.m.-6 p.m.) could be achieved by providing signal priority for buses. Average bus delay time was reduced in the range of 16%-20% and 5%-14% during peak periods, respectively. The Phase II study is developing a prototype system using GPS and wireless technologies to provide signal priority for buses. A test site at Como and 29th Avenues was selected, and the researchers will test the Minneapolis and University of Minnesota wireless coverage at the intersection.