Heuristic Algorithm for Priority Traffic Signal Control

consider the multiple requests for priority in a way that is not disruptive, or inefficient, to other traffic. Other factors, such as occupancy and schedule adherence, are important considerations that can be used to manage which priority requests should be served, but it is still likely that multiple transit vehicles will desire priority service. The approach presented in this paper is an integrated framework in which priority requests represent the different control considerations, including preemption, priority, and coordination. The first formal treatment of serving multiple priority requests was by Head et al. (10). They formulated a mixed-integer nonlinear programming problem based on a precedence model of the dual-ring controller (11). This formulation is intuitive, but difficult to be implemented especially in an embedded environment, such as an embedded Linux system. He modified this formulation to be mixed-integer linear, which improved the solvability, but it still depends on using commercial optimization solvers such as CPLEX (12). This research has been motivated by the recent advances in vehicle positioning, vehicle-to-vehicle communications, and vehicleto-infrastructure communications. This paper presents a heuristic algorithm for integrated consideration of priority requests at any one time from multiple vehicles of different classes in the environment of IntelliDrive. For example, two or three transit buses may arrive at a coordinated intersection from different directions and request service by different signal phases, or several emergency vehicles may approach an intersection from different directions. Integration of the multiple requests for priority and the desire to operate the signal as part of a coordinated, actuated system require new signal control logic.