An adaptive transit signal priority strategy using GPS/AVL and wireless communication systems

Current signal priority strategies implemented in various US 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 were detected without the consideration of bus readiness. The objective of this study is to integrate the already equipped GPS/AVL system on the buses and develop an adaptive signal priority strategy using wireless communications that could consider the bus schedule adherence, number of passengers, vehicle location and speed. City of Minneapolis recently deployed wireless technology to provide residents, businesses and visitors with wireless broadband access anywhere in the city. Communication with the roadside controller for signal priority may be established using the readily available 802.11x WLAN (Wireless LAN) or the DSRC (Dedicated Short Range Communication) 802.11p protocol currently under development for wireless access in vehicular environment. This paper describes our proposed priority strategy, its evaluation using microscopic traffic simulation, and the embedded prototype systems.