For the management and planning of urban rail lines, operators can draw upon tools that use train circulation models as well as passenger assignment models. However, these two kinds of simulation models are independent. They do not interact as they do in reality. Yet on certain highly congested lines, high train frequency and large passenger volumes can turn a small incident into a delay on the entire line. Our research presents an integrated model for the simulation of a fixed block urban rail line in interaction with passenger assignment. This operational model introduces new management strategies or rolling stock feature solutions to improve the quality of service on the line. A discrete-event approach simulates the progress of the runs on the line, and the representation of the passengers by origin-destination flow per time step makes it possible to effectively simulate lines with large flows. An application to Line 13 of the Paris metro illustrates the model on a real case of congestion. Sensitivity analyses on the level of demand as well as on service characteristics demonstrate the utility of this integrated approach.