Impact Assessment of a Cooperative Bus-Holding Transit Signal Priority Strategy

In this study, a cooperative Transit Signal Priority (TSP) strategy utilizing transit vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication is proposed and assessed. The proposed Bus-Holding Transit Signal Priority (BHTSP) is implemented and evaluated for a detailed isolated intersection constructed in VISSIM microsimulation software resembling the intersection of Alumni Mall and Main Street in Blacksburg, VA, USA. The impact of the proposed strategy was assessed for Blacksburg Transit vehicles arriving at the major Squires Eastbound bus stop, using high quality data that includes up-to-date vehicle flows, signal timing, transit schedules, and actual transit arrival, departure and dwell times. An advanced vehicle actuated control logic was implemented using the VISSIM COM Application Programming Interface (API) to emulate communications between transit vehicles and signal controller. When a transit vehicle is approaching the bus stop, the transit vehicle that is dwelling at the stop is forced to hold past its dwell time and wait for the upstream vehicle to arrive and dwell, in order to subsequently generate a priority request that would serve more than one transit vehicle convoying from the stop towards the intersection. This strategy results in an improved TSP performance by reducing the number of priority requests, missed TSP calls, and reducing the adverse effects on non-transit traffic at the main arterial. The proposed BHTSP was further fortified by utilizing V2I communications, the Connected BHTSP (C-BHTSP) strategy has resulted in 61% reduction of transit delay in the network compared to the base scenario, alongside a 38% reduction in early green priority requests, reducing the incurred arterial vehicle delay by 32%, and reducing total additional system stops by 51% compared to conventional TSP strategy.