Hamburg U Bahn Type DT3

Description

With the continued expansion of the subway network in the 1960s and 70s, and the desire for greater efficiency in operating procedures resulted in development of a new type of subway units based on the older DT1 and DT2 units. The DT3 resembles to the DT2 in appearance but shows many technical differences. Technically the DT3s were based on the DT1s which were compatible to DT3 after some customization, both types can be coupled. Instead of two cars the DT3 feature a third car which is 10.72 meters long. Because of the greater overall length of a 9-car train made up of three units instead of an 8-car train made up of four units of DT1s or DT2s some platforms on the U1 line (e.g. on the Langenhorn branch) had to be extended. The DT3 trains are more powerful than its predecessors; they have been equipped with additional traction motors and therefore have got a much stronger acceleration. Thus, the maximum acceleration is 1.2 m/s², in contrast to the DT2 with 0.8 m/s². Moreover, the speed limit was increased to 80 km/h (50 mph) again, because the units were mainly built for the longest subway line in Hamburg, the U1 line.

Refurbishment

In the mid-1970s the cars got loudspeakers inside and on the roof outside for station announcements. After a first small refurbishment in the early 1980s, in the 1990s many of the units have been rebuilt and received a newly designed front and a new interior design, such as windows between the cars and between the driver's cab and passenger interior. The rebuilt became necessary due to structural issues the DT3 faced just like their predecessor as both types were actually only designed for a lifespan of 20 years. A total of 68 units were involved into the refurbishment, the rest of the units were replaced by new DT4 units, retired and scrapped until 2003. The rebuilt units are now called DT3-E.

In June 2015, the operator Hochbahn announced another refurbishment for ten DT3-E units to extend their lifespan for ten more years.

The DT3-LZBs

For experiments with driverless trains on a larger scale, the six units 9963/64/65-9978/79/80 (now 921-926) have been converted for automatic operation. After a long trial run on the test track parallel to the U1 line between the maintenance workshop Farmsen and Berne station, the six now called DT3-LZB units were used between Volksdorf station and Großhansdorf station on the Walddörferbahn branch for driverless operation. The automatic operation was observed by a conductor permanently sitting in the cab, they also had to dispatch the train in stations. The experimental operation ended on 8 January 1985, since then the units are used together with the other DT3 under normal conditions.

The cars mainly differ by the square headlights instead of round headlights and a smaller interior in the first cab car of the units as the LZB computers needed more space than available in the cabs. When it came to the refurbishment of many DT3 units in the 1990s the DT3-LZB only received the interior refurbishment and did not get their front replaced as it was unclear for a long time whether the six units would be retired or would remain in service. They are still in service in 2016 and are the last cars with the old red front since 2002 which has always been prone to rust.

Today

In the early 2000s, the DT3-E and DT3-LZB were replaced by DT4s on U1 line and were moved to U2 and U3 line. After 2009, the DT4 unit also replaced the DT3s on the U2 line and the rest got moved to U3 line and since then, they are used on U1 line again in peak hours as well. They are being replaced by the new DT5. Retirement of the remaining trains started in 2015 with the units 802, 825, 838, 856, 922 and 923 being permanently out of service as of September 2016 and some of them being stripped to get spare parts for the rest of the fleet. With the ongoing DT5 delivery DT3 service is planned to be limited to peak hours only from Summer 2017 on.