D' stockThe fleet of 75 six-car all aluminium D78 stock was introduced in stages between 1980 and 1983.
- District line (all sections except between Edgware Road and High Street Kensington)
- Refurbished by Bombarder Transportation UK, Derby 2006-2008
- Manufactured by Metro-Cammell of Birmingham
The trains comprise two three-car units - driving motor cars, trailers and driving or non-driving motor cars.
They are similar in length to the seven-car trains they replaced, each car being longer than usual. This had the advantage of lessening the amount of wheel-sets required per train, thereby reducing maintenance costs and through being lighter, lessening train noise and vibration.
There are concealed fans in the ceilings, which were later boosted by additional fans. Together with opening quarterlights a high degree of comfortable ventilation was afforded.
The D78 stock shares many similarities with the 1973 Tube stock that runs on the Piccadilly line, particularly in its traction package and wheelsets. The D78 stock has Tube-sized wheels. Traditionally, surface stock has always had 1,067mm wheels, whereas Tube stock has 790mm wheels. The smaller wheels allowed there to be more headroom in the cars, and was also an attempt to reduce maintenance costs by reducing the different types of wheels and bogies in use.
Traction brake controls comprise a right-hand 'fore and aft' vertical lever incorporating the 'dead man' device, instead of the previous left hand rotary operated controller.
For the first time with surface stock, the doors consist of four pairs of single leaf doors per side.
Seating is mostly longitudinal with a double pair of transverse seats in the centre of each car.
The Fleet was refurbished between 2006 and 2008, and painted in London Underground colours. The refurbishment programme also includes a complete interior refresh, including car end windows and CCTV added to increase security. Significant improvements to the passenger information system were made with saloon dot matrix station/destination displays and a new digital voice announcer.
There are three types of D78 car - DM (driving motor cars - fitted with drivers controls and traction motors), UNDM (Uncoupling non-driving motor cars - fitted with traction/control equipment but no drivers controls or accommodation, and fitted with a small cabinet allowing uncoupling and shunting), T (trailer coach with no driving controls or traction equipment).
|Length||60ft 3.25in||59ft 5.5in||59ft 5.5in|
|Height||11ft 10.5in (3.62m)||11ft 10.5in (3.62m)||11ft 10.5in (3.62m)|
|Width||9ft 4.25in (2.85m)||9ft 4.25in (2.85m)||9ft 4.25in (2.85m)|
|Weight||27.46 tonnes||26.11 tonnes||18.40 tonnes|
|Seating capacity per train||280|
|Standing capacity per train||547|
|Train capacity - six cars||827*|
As part of the upgrade of the sub-surface lines, new trains began to be introduced in 2010 on the Metropolitan line.
By 2015, the entire sub-surface fleet will have been replaced with new rolling stock, which will be known as S stock. The Metropolitan line will be followed by the Circle and Hammersmith & City lines, and finally the District line.
*Total train capacity is based on 4 passengers per m2