Picture of a the a station of the U-Bahn system of Dortmund, Stadtbahn Dortmund, with a train tram ready for departure. The Dortmund Stadtbahn is a light rail system in the German city of Dortmund and is integrated in the Rhine-Ruhr Stadtbahn network. Its network consists of eight lines and is operated by Dortmunder Stadtwerke, which is operating under the brand DSW21 since 2005