abstract: Smirnov decomposition Theorem is concerned with one-dimensional normal currents. The aim of this talk is to show how this result can be fruitfully exploited in the framework of transport theory. In particular we will prove a lower semicontinuity for concave functionals on 1-dimensional transport measures occuring in models with economy of scales (branched transport). In the context of transport with congestion, we will also deduce that the optimal flow for the Beckmann's problem can be identified as an optimal transport density for the Wardrop's problem.