Transition Methods in Traffic Signal Control

Abstract

“Transition” is simplistically defined as the process of switching from one timing plan to the next. Doing so can disrupt traffic flow to varying degrees, with potentially lasting effects. Avoiding or mitigating these effects is of particular interest in the context of more frequent timing plan changes, as may be expected under traffic-responsive or adaptive traffic control. This paper compares several transition methods, for each of several congestion levels, to determine which methods exhibit the least vehicle delay. A policy is introduced for dynamically selecting an effective transition method based on current traffic conditions. This study uses new transition capabilities recently added to the CORSIM simulation, based on current transition functionality of Eagle, Econolite, NextPhase, and Naztec controllers. Results confirmed that Short-way transition is the most effective in general, but also showed that under congested conditions, Add transition performed as well or better. Dwell transition exhibited higher delays. Evaluation of several parameter settings also demonstrated minor benefits to configuring more generous Add constraints and slightly more conservative Subtract constraints.