2021 Volume 76 Issue 5 Pages I_21-I_39
This paper reviews the recent advances in the theory of dynamic traffic equilibrium assignment problems. We mainly discuss a Lagrange coordinate system approach enabling us to analyze the complex network traffic flows transparently. Two types of description of traffic within the approach—traditional fluid approximation models and emergent atomic/particle models—are explained in comparison. Based on the features and relationships of each model and the results on the mathematical properties of equilibrium solutions, the direction of future developments utilizing the superiority of both models is briefly discussed.