Introduction The Fixed Charge Network Design Problem (FCNDP) consists in selecting a subset of edges from a given network, in such a way that a set of commodities can be transported from its origins to its destinations. The objective is to minimize the sum of fixed costs (depending on the selected edges) and variable costs (depending on the flow of commodities on the edges). There are several variants of FCNDP in the literature, each of which considers a particular objective function or takes into account specific additional constraints. Herein we are interested in a specific variant of the FCNDP, namely Fixed Charge Network Design Problem with User Optimal Flow (FCNDP-UOF). This problem combines the FCNDP with multiple shortest path problems.