The Karlsruhe Stadtbahn is a German tram-train system combining tram lines in the city of Karlsruhe with railway lines in the surrounding countryside, serving the entire region of the middle upper Rhine valley and creating connections to neighbouring regions.

As of 2013[update], AVG quotes the size of the part of the Karlsruhe Stadtbahn system that is not operated by DB as 262.4 kilometres (163.0 mi),[4] with 12 lines[1] serving 190 stations.

The section between Pforzheim and Wörth Badepark runs mostly unchanged, with only changes in arrival and departure times.

[11] Every 30 minutes (off-peak) Karlsruhe attempted to create a network of street and interurban tram lines for the development of the surrounding countryside, modelled on the Oberrheinische Eisenbahn-Gesellschaft.

The success of the Alb Valley Railway encouraged the Karlsruhe planners in the 1960s to connect the northern surrounding outskirts by a modern tram/stadbahn system as well.

For this it negotiated with Deutsche Bundesbahn to use the Hardt Railway (Karlsruhe-Neureut-Eggenstein-Leopoldshafen), sharing with the local goods traffic, and reached an agreement at the end of the 1970s.

In 1986 and 1989 the Stadbahn was extended north to Leopoldshafen and Linkenheim-Hochstetten and to the Forschungszentrum Karlsruhe, again sharing existing railway tracks.

Since the remaining goods traffic was hauled by diesel locomotives, the electrification of the line with the tramway’s 750 V DC system did not cause technical problems.

This line included single-track sections in the main streets of the local centres of Blankenloch, Forchheim and Mörsch.

[3] The tram and rail networks were linked by building a connecting line between Durlacher Allee and Grötzingen station.

The tunnel shortened the travel time for the Stadtbahn through the pedestrian zone and improved the stability of the timetable.

In addition, the platforms of the station's tunnel have pedestals that are about 15 metres (49 ft) long with a height of 55 cm (22 in) above the rail so that the first two doors of Stadtbahn trains have step-less entry.

In the two-area system served by the GT8-100D/2S-M Flexity Swift vehicles, 55 cm (22 in) high platforms were built to provide step-free entrances.

The Rhine-Neckar S-Bahn on the other hand, uses 76 cm (30 in) high platforms for accessibility on the Durlach–Bruchsal section, but only at Durlach and Bruchsal stations.

There are currently a few stops in Karlsruhe city with platforms providing level access to two-system vehicles (such as those used on lines S 4 and S 5).

The proposed urban tramways in Bruchsal, Rastatt, Baden-Baden and Landau failed to proceed, however, because of the political resistance of local politicians.

However, the standardised assessment did not show a cost-benefit ratio worth funding for any of the options examined, so the project was not pursued any further.