Trains On The Berlin U-Bahn

The trains on the Berlin U-Bahn are split into two categories: Kleinprofil ("small profile", used by the U1, U2, U3 and U4) and Großprofil ("large profile", used by the U5, U6, U7, U8 and U9) lines. The names refer to the size of the train's coaches. Großprofil coaches have a width of 2.65 metres and a height of 3.40 metres, and Kleinprofil coaches are only 2.30 metres wide and 3.10 metres high. Therefore the trains have to operate on separate networks.

Both networks have standard gauge (1435 mm) track and are electrified at 750 Volts DC. Because Großprofil and Kleinprofil trains use different types of power supply the trains cannot normally operate on the same route. However, on the Nord-Süd-Bahn in the years between 1923 and 1927 and on the E line (today's U5) between 1961 and 1978, Kleinprofil trains with specially adapted power pickups ran on Grossprofil tracks. They were fitted with special wooden boards on the sides to close the gap between platform and train. These wooden boards were jokingly called Blumenbretter ("flower boards").

Also, the polarity of the power rails differs. On the Kleinprofil lines the power rail is positively charged and the track is negative, on the Großprofil lines it is the other way around. In East Berlin the polarity of the track section Thälmannplatz/Otto-Grotewohl-Straße - Pankow, was the same as on the Großprofil lines. After reunification, this exception to the normal Kleinprofil polarity was reversed by the BVG, even though there are benefits to this arrangement (there is less corrosion of metal parts in the tunnel with the Großprofil polarity).

The newest types of U-Bahn are H for the Großprofil and Hk for the Kleinprofil. The oldest vehicles still in service are of the F74 type (Großprofil) and of the A3-64 type (Kleinprofil).