Analytical model of traffic delays under bus signal preemption: Theory and application

Major emphasis has been placed in recent years on the improvement of the operations of existing transportation facilities, using Transportation Systems Management strategies. Accordingly, preferential treatment of high occupancy vehicles is playing an increasing role in transportation projects. This paper deals with one of these strategies, the priority treatment of buses at signalized intersections. Such treatment is aimed at improving the capacity of intersections. The paper develops an analytical model of delays at signalized intersections under a bus preemption scheme. The analysis is presented for the simplest case, i.e., two intersecting one-way streets. The results suggests that the benefits of bus preemption can be increased by properly adjusting several design parameters such as cycle and phase duration of the preempted phases as well as the non-preempted parameters. The model outlined in this paper is applicable to any situation in which stochastic variation is introduced into the signal cycle as well as to bus preemption. Consequently, other potential applications of the model include the design/analysis of traffic actuated signals, and pedestrian actuated signals.