With special RegioTram tramcars, continuous trips between the Deutsche Bahn heavy rail network and Kassel's city tram network are easily possible, thus avoiding transfers requiring long walking distances between trains of the regional rail system and trams of the Kassel city system.

The implementation of the RegioTram project includes various interlocking measures to improve local public transport in Kassel.

RegioCitadis type vehicles manufactured by Alstom in Salzgitter were delivered in July 2004, and took over the operation on this line on 8 May 2005; the borrowed Saarbahn tramcars were then returned.

The former tram-train runs over the non-electrified railway through Waldkappel were replaced by tram "express" trips that do not operate at all stops along the route.

[citation needed] Starting 1 June 2006, RegioTram operations from Kassel Hauptbahnhof, through Baunatal, Guxhagen and Körle, to Melsungen, began.

Between 16 September 2007 and the timetable change in December 2007, the RegioTram Line 9 (RT9) operated in advance from Kassel Hauptbahnhof to Treysa.

[citation needed] RegioTram routes in Kassel changed 19 August 2007 (RT4), 16 September 2007 (RT3 and RT5) and December 20097 (RT9) from running to the Innenstadtring (Inner Rign Road) in downtown, and instead to Leipziger Straße.