This paper develops a theoretical model for freight transport characterized by competition between
means of transport, the road and maritime sectors, where modes are perceived as differentiated
products. The road freight sector is assumed competitive. In contrast, the freight maritime sector is
characterized by oligopolistic behavior, where shipping lines enjoy economies of scale. When both
shipping lines decide to merge, two post-merger situations can be reached. In one of them the liners production processes remain separate; in another economies of scale are further exploited. An empirical application to the routes Valencia-Antwerp and Valencia-Genoa is undertaken. It is shown that, for both types of merger, user surplus increases when transport services are weakly
differentiated and economies of scale are sufficiently small. These conditions also guarantee that a
merger is socially beneficial.