A Quasi-dynamic Traffic Assignment Model with Time-dependent Queues

A quasi-dynamic traffic assignment model is proposed,in which the traffic demand is time-varying and the queues are time-dependent under the quasi-dynamic condition. The proposed model can estimate simultaneously traffic flows and queues in the network at various time intervals andlor under different traffic conditions, especially when the total traffic demand exceeds the network capacity in the peak period. By carrying queues over from one time interval to the next, the temporary over-loading of the network which characterises peak periods can be allowed for. Steady state conditions are assumed within each time interval, so avoiding difficulties with first-infirst-out (FIFO) in the queuing process. A mathematical programming model, where optimal solution satisfies the user equilibrium condition, is developed for the timevarying traffic assignment with time-dependent queues. Numerical examples are given to illustrate its applications.