Entered service: 1980
Built by: Metro-Cammell of Birmingham
Lines: District Line (everywhere except between Edgware Road and High Street Kensington)
Length per car: 18.37m (driving motor car), 18.12m (uncoupling non-driving motor car)
Weight: 27.46 tonnes (driving motor car), 26.11 tonnes (uncoupling non-driving motor car), 18.40 tonnes (trailer)
Between 1980 and 1983, 75 six-car D78-Stock trains were introduced to the District Line. Each train comprises two three-car units (a driving motor car, a trailer and either another driving car or a non-driving car).
There are three types of D-Stock car: Driving motor cars are fitted with driving controls and traction motors; uncoupling non-driving motor cars are fitted with traction equipment but no driving controls or accommodation, and have a small cabinet to allow uncoupling and shunting; and finally the trailer coach, which has neither driving or traction controls.
Despite being surface stock, D-Stock is similar to 1973 Tube stock. It has the same size wheels and a similar traction package. Surface stock usually has wheels of 1,067mm in diameter (compared with the 790mm wheels on Tube stock). But D-Stock having the smaller Tube wheels allows more headroom and reduces maintenance costs by lowering the number of different types in use.