The Cologne–Aachen high-speed line is the German part of the Trans-European transport networks project high-speed line Paris–Brussels–Cologne. It is not a newly built railway line, but a project to upgrade the existing railway line which was opened in 1841 by the Rhenish Railway Company. When it was continued into Belgium in 1843, it became the world's first international railway line.

The Rhine-Ruhr S-Bahn is a polycentric and electrically driven S-bahn network covering the Rhine-Ruhr Metropolitan Region in the German federated state of North Rhine-Westphalia. This includes most of the Ruhr, the Berg cities of Wuppertal and Solingen and parts of the Rhineland. The easternmost city within the S-Bahn Rhine-Ruhr network is Unna, the westernmost city served is Mönchengladbach.