Dortmund's public transport is run by DSW21 and integrated into the VRR regional network. The U-Bahn (actually a Stadtbahn — partly underground, partly surface-running trams) covers the city centre and most of the inner suburbs. Line U42 and U45/U46 are the most useful for visitors, connecting the Hauptbahnhof to the Westfalenpark and Signal Iduna Park. Line U47 and U49 head into the northern and southern suburbs.
Tickets are available at machines at every station. A single ride within the city centre zone costs around €3; a day pass for the entire city is more economical for multiple journeys. The transport network is integrated with Bochum and Essen, so a day pass also covers travel across much of the Ruhr. The city centre is compact enough to walk once you are there; a bike is useful for reaching Zeche Zollern or Rombergpark in the outer districts.