A new dynamic traffic model and the existence and calculation of dynamic user equilibria on congested capacity-constrained road networks

This paper presents a new dynamic model of peak period traffic flows on congested capacity-constrained urban road networks. While respecting the first in, first out (FIFO) discipline of road traffic queues and the exit capacities of road links, the model determines the (time-varying) costs incurred in traversing the various routes when (time-varying) route inflows are specified. It is proved that if this model is used to find route costs then a dynamic user equilibrium exists. The paper also gives four optimisation formulations of the dynamic user equilibrium problem. A descent algorithm is suggested; there is, as yet, no proof that the algorithm converges to an equilibrium. Finally, the paper introduces a family of alternative methods of determining dynamic flows which (almost) satisfy FIFO, and specifies one member of this family in some detail. These alternative methods arise as a consequence of using different ways of specifying the priority of a vehicle or a group of vehicles.