The U12 is a former BerlinU-Bahn line. It existed between 1993 and June 2003, as a peak-time and night line between Ruhleben (today U2) and Warschauer Straße (today U1) stations. It resumed its old route for a short period of time between May and November 2015, due to repair work taking place in the Gleisdreieck station.
Route
The route remained more or less the same throughout its history. Before October 1995, the U12 only went as far as Schlesisches Tor. The connection between Schlesisches Tor and Warschauer Straße was restored in October 1995 and therefore the U1, U12 and U15 lines were extended to Warschauer Straße.
Special
On 18 August 2006, this line was in service again as a replacement service for the U2 between Gleisdreieck and Ruhleben. Bridge building works between Gleisdreieck and Bülowstraße prevented trains running on that track until 18 March 2007.
In 2011 line U12 was brought back into existence again due to repair work currently being undertaken at Gleisdreieck, however it was only after protests by passengers who had to transfer at Wittenbergplatz to continue their journeys on lines U1 and U2 that line U12 was re-established for the second time.