Conditional Signal Priority for Connected Transit Vehicles at Urban Arterial Roads

To improve the service reliability by utilizing real-time transit vehicles data, a novel conditional signal priority method is proposed. The method has four features: 1) the accurate management of a transit vehicle's headway; 2) innovative use of triggered phases, to flexibly control the departure time of transit vehicles based on headway deviation; 3) availability at actuated-coordinated intersections, to ensure the rapid passing of arterial traffic, while taking into account the time-varying needs of motorized vehicles; 4) an alternate passing opportunity providing for the transit vehicle that cannot enable the priority mode, to ensure that each transit vehicle can pass the stop line at a relatively suitable time. Simulation results showed that the proposed signal priority method can significantly improve the headway regularity in the transit system compared with the methods of traditional conditional signal priority, unconditional signal priority, and no signal priority, although the traffic efficiency of vehicles is slightly reduced.