A stochastic user equilibrium path flow estimator

The paper sets out a path flow estimator suitable for use in conjunction with urban traffic monitoring, control and guidance. Travel time for each link in the network is partitioned into undelayed travel time and delay. The links are assumed to be of two types. For the first type of link, an external estimate of flow and travel time over the estimation interval is provided. The second type of link is characterised by a finite capacity, and delay is incurred where demand would otherwise be in excess of capacity. Demand is determined by a logit route choice model. An equivalent convex programming problem is formulated and an iterative solution procedure is set out. The estimation of the dispersion parameter in the logit model is discussed, and a column generation method to avoid path enumeration is proposed. Diagnostic procedures and a number of other practical enhancements to the procedure, in particular the incorporation of prior information on the relative magnitudes of origin-destination movements, are considered.