(suburban railway), overcoming the boundary between trams and trains. Its logo does not include the green and white S-Bahn symbol used in other German suburban rail systems and the symbol is only used at stops and stations outside the inner-city tram-operation area.

The idea to link tram and railway lines with one another in order to be able to offer an attractive transport system for town and outskirts was developed in Karlsruhe and implemented gradually in the 1980s and 1990s, with the system commencing operation in 1992. This idea,