The railways perform an important function in providing local transport in densely populated industrial areas. Attractive services are being introduced to induce motorists to switch over to public transport. This would also help ease the burden on the environment. Over the years billions have been spent on modernizing fast metropolitan railway networks (S-Bahn) in Berlin, Cologne, Frankfurt am Main, Hamburg, Kassel, Munich, Nuremberg, the Ruhr district and Stuttgart. They have been linked with underground, tram and bus systems to form “transport grids” in nearly all densely populated areas. Passengers may switch from one system to the other using the same ticket.