Proposed Methodology of Optimizing Transitioning Between Time-of-Day Timing Plans

Abstract

Timing plans for coordinated signals are developed online using real-time traffic data collected by detectors or offline using traffic data previously collected but still representative of the period in which the timing plan is to be implemented. The timing plans developed using offline techniques are generally known as time-of-day (TOD) timing plans as they are generally implemented during a specific time of the day. One downside of the TOD timing technique is the handling of coordination parameters--defined by cycle length, phase split, and offset--when one plan is transitioning to the next plan. This paper presents a methodology to optimize traffic flow during the transition period. The methodology, based on dynamic quadratic optimization, achieves synchronization of coordination parameters through an optimum number of cycles and an optimum number of increments (or decrements) of the coordination parameters. The proposed transition period optimization method has the advantage that the user does not need to specify minimum and maximum cycle lengths in the optimization process, as is the case with current methods. Preliminary simulation results that compared the proposed methodology to transition methods embedded in CORSIM showed that it has the potential of reducing queue delay, particularly on minor street approaches. The delays on major street approaches were comparable and similar in both scenarios in which traffic volumes were increasing or decreasing between the succeeding plans. Additional simulation runs involving various scenarios of geometric, traffic, and signalization conditions as well as field evaluation are needed before the efficacy of this method over current methods used in practice can be ascertained.