Congestion Modelling

Transportation researchers have long struggled to find satisfactory ways ofdescribing and analysing traffic congestion, as evident from the large number of often competing approaches and models that have been developed. This paper aims to provide a review of the literature on this topic. The paper starts with the modelling of homogeneous traffic flow and congestion on an isolated road under stationary conditions. We set up the supply-demand framework used to characterize equilibrium and optimal travel volumes. Next, an overview of macroscopic and microscopic models of nonstationary traffic flow is given. We then describe how trip timing can be modelled, and discuss the essence of dynamic equilibrium. The paper next reviews the principles of static and dynamic equilibrium on a road network in a deterministic environment, and then identifies equilibrium concepts that account for stochasticity in demand and capacity. Finally, conceptual and practical issues regarding congestion pricing and investment on a network will be addressed