Modelling the Spill-back of Congestion in Link Based Dynamic Network Loading Models: a Simulation Model with Application

摘要

The spill-back of congestion on a network is the propagation of congestion backwards from a link to its upstream links. It occurs whenever the downstream queue is so large that it impedes the incoming speed and flow of vehicles. This very common situation in many urban networks is usually caused by recurrent congestion on a day-to-day basis. This paper provides a way to adjust some existing network models in order to take this complicated phenomenon into account. There are a number of different approaches to dynamic network loading and assignment that have been studied, such as: heuristic generalisation of within-day static methods (Hammerslag, 1988; Janson, 1989), exit-function methods (merchant and Nemhauser, 1978; Carey, 1986a,b; Friesz et al., 1989; Wie et al., 1990; Boyce et al., 1991), packet-approach (Cascetta and Cantarella, 1991; smith and Wisten, 1996) continuous time link models (Astarita, 1996; Wu et al., 1995; Xu et al., 1996; which identify conditions for the satisfaction of FIFO). these models are all capable of performing Dynamic Network Loading (DNL), i.e. the reporudction of within-day variable link (or local) performances given the path flow rates, and have proved to be useful, both to evaluate traffic flows, and, to simulate the effects of control strategies on users' behaviour. However, none of these models adequately address the problem of the backward propagation of congestion, and some do not even rule out overtaking between users (FIFO rule).