The S-Bahn started operating at the timetable change in December 2002 on the S-Bahn tracks, which are now operationally separated from the main line. The tracks on the high-speed line are used by regional and international express train services. Until the opening of the Cologne/Bonn Airport station in mid-2004, line S 13 of the Cologne S-Bahn (the southern part of the Rhine-Ruhr S-Bahn) operated to Düren, but since then line S 12 has run from Au (Sieg) via Hennef, Troisdorf and Cologne to Düren. Köln-Weiden West station, which serves as a link to Cologne Stadtbahn line 1, was opened on 28 May 2006. In particular, it is intended to facilitate arrivals and departures at events in the RheinEnergieStadion. The single-track S-Bahn line was duplicated over a length of 1.6 km between Buir and Sindorf to allow the equalisation of S-Bahn frequencies between Düren and Cologne. At night, the S13 runs beyond Horrem to Aachen and back. This gives the region a better connection to Cologne/Bonn Airport.