On a congested transport network, a marginal trip exerts a congestion effect on the rest of traffic. From the polluter-pays principle in economic theory, the associated cost must be charged to the marginal trip-maker to achieve system optimum. This makes the evaluation of the marginal congestion cost a valuable objective, though not an easy one due to the dynamic and spatial nature of traffic phenomena. Besides the classical, static treatment, some dynamic models have been developed, most of them restricted to a fixed-capacity bottleneck. This paper develops the dynamic analysis of the social cost of congestion in two directions.
First, analytical formulae are provided to deal with a multiclass flow in a bottleneck with time-varying capacity. Then, a set of increasingly complex situations are investigated: the sequence of bottlenecks along a route in the network; the set of routes of a given origin-destination pair. Lastly, helpful dynamic congestion indicators are designed for sub-networks and trip-end zones. An application to the major motorway network in France is given for the purpose of illustration.