and mandates a so-called "Benefit-Cost Quotient" above 1.0 (i.e. "benefits" exceeding "costs") and an extension to Stein is unlikely to meet that as only the newly built stretch would be taken under consideration. Northern end Another extension variously suggested since the extension of tram line 4 northwards to "am Wegfeld", a point due West of the current endpoint of U2 at the airport, was politically decided, is towards the tram/bus interchange point "am Wegfeld" in the :de:Knoblauchsland. While various studies have failed to reach the required benefit cost ratio above 1, the current bus service between the airport and "am Wegfeld" (line 33 with onward service to Fürth Hauptbahnhof and line 30 with onward service to Erlangen) overlaps to a 10 minute headway, the same as U2 service between the airport and Ziegelstein station. In addition to linking the airport to the interchange point and relieving the residential areas of bus traffic, such an extension would also offer an interchange between tram line 4 (which is planned to be extended towards Erlangen in the course of the "Stadt-Umland Bahn“ project) and U2 (otherwise only possible at Plärrer station) and relieve the airport of the role as a bus/subway interchange point, that it only gained in the course of the reorganization of bus traffic in the north of Nuremberg in the course of the opening of the tram extension to "am Wegfeld" in 2016. Branches or infill stations There are also various plans for branches and an additional infill station on the last stretch towards the airport. Including a proposed "Marienberg" station which was already indicated as a possibility in promotional material released during the opening of the extension towards the airport. Rolling stock Prior to the introduction of automatic operation in the course of the opening of U3 (2008) and the conversion of U2 to all automatic operation (2010), the line was served by the same VAG Class DT1, VAG Class DT2 and even MVG Class A vehicles as U1. However, with the conversion of U2 to automatic operation, those vehicles were withdrawn from service or switched to exclusively operating on U1, the last remaining all manual line. Some older units of Class DT1 still contain displays in their interior that can be switched between "U1", "U2" and the obsolete "U11" and "U21" (since abandoned designations for truncated runs on the U1 or U2 corridor), but they haven't served any