The Ruhr–Sieg railway is a 106 km long double-track, electrified main line from Hagen to Siegen via Iserlohn-Letmathe, Finnentrop and Kreuztal in the German state of North Rhine-Westphalia. The line, which has many tunnels, runs primarily through the valley of the Lenne. South of Altenhundem it crosses the watershed between the Lenne and the Sieg. The line was opened between 1859 and 1861 and is one of the oldest railways in Germany.

The Düsseldorf-Derendorf–Dortmund Süd railway is a partially closed line in the German state of North Rhine-Westphalia from Düsseldorf-Derendorf station to Dortmund South station. Parts of it are still busy, including two sections used for the Rhine-Ruhr S-Bahn.