Delay function for signalized intersections in traffic assignment models

The consideration of delay at signalized intersections improves the accuracy of equilibrium flows obtained from traffic assignment models. This delay depends not only on physical specifications of the intersection, intersection signal timing, and traffic volume and its composition but on drivers' behavior and specific traffic culture in each country. This paper proposes a delay function for traffic assignment models, which considers the special drivers' behavior in Iran. Unlike the existing models such as the Highway Capacity Manual model, the proposed delay function has modest data requirements on intersection characteristics, and this ensures the easy use of this function in a real traffic assignment model. To evaluate the proposed function in a real network, the traffic assignment model of the city of Mashhad, Iran is used. In two different scenarios, the equilibrium flows obtained when the proposed function is applied and those obtained when a simple uniform delay function is used are compared to the observed traffic flows. In a comparative sense, the results show the better performance of the proposed function in estimating the equilibrium flows.