Review of Models Combining Traffic Assignment and Signal Control

This paper reviews a class of models that combine equilibrium traffic assignment and intersection control into a single analysis framework under the assumption of flow-responsive signal settings. The most significant feature of these models is their capacity to take into account explicitly the mutual interactions between signal control policies and user route choices; such interactions are usually disregarded both in ordinary traffic assignment models and in traditional traffic engineering practice. After defining the combined traffic assignment and control problem, and reviewing alternative formulations and solution algorithms, this paper discusses possible approaches to modeling the various types of link interactions that arise from the joint use of intersections by competing traffic movements. Important conceptual issues and implementation aspects are considered, and their potential policy implications are emphasized. The main conclusion of the survey is that, while the theoretical properties of combined traffic assignment and control models have been studied over the last two decades and are now well understood, there seems to be a significant lack of empirical results and real-world applications, that are needed in order to promote the transfer of this modeling approach from research to professional practice.