We propose a model in which a utility maximizing traveler assigns flow across an entire
network under a flow conservation constraint. Substitution between routes depends on how much
they overlap. This model can be estimated from route choice data, where the full set of route
alternatives is included and no choice set generation is required. Nevertheless, estimation requires
only linear regression and is very fast. Predictions from the model can be computed using convex
optimization and is straightforward even for large networks.