An automatic phase and sequence design method for isolated intersections

Phase and sequence design is the first step in the signal control of an intersection. Poor phase and sequence design may result in inefficient control strategy. An automatic process is proposed to generate the optimal phase and sequence based on traffic flow, saturation flow and intersection geometry. Considering traffic operation efficiency and safety, the principles and evaluating indexes of phases are discussed and analyzed first. Then the following four issues are discussed in detail. First, symmetry phase and each phase for an entrance are compared in capacity, conflict points, delay, equilibrium of saturation, inter-stage loss and other indexes; second, develop the threshold from permitted to protected left-turn phasing; third, analyze the sequence of the phases which are essentially due to the position of conflict points; and fourth, the calculation and the thresholds of Overlapped phase are discussed. Considering these four issues, the automatic process of phase generating is established. © 2010 ASCE.