Transport for LondonRolling stock
1996 stock
The two main types of train on the Tube are not fully interchangeable between lines, although there have been many instances where stock has been cascaded from one line to another. For instance the 1983 stock introduced to the Jubilee Line displaced the 1972 stock to the Northern Line which in turn meant that 1959 stock from there was able to be transferred to the Bakerloo Line to replace the 1938 stock which was being withdrawn.
The basic difference between stock is size. The original City & South London Railway running tunnels were 10ft 2in (3.1metres) in diameter. Later lines saw the internal tunnel diameters rise to 3.6 metres, and 3.8 metres with the Victoria Line.
1967 stock
Besides diameter, other physical features such as curvature, platform length and in recent times the signalling system all mean that often rolling stock is now increasingly only able to be used on one specific line.
The Central and Victoria Lines platforms are 400ft long and have different Automatic Train Operation signalling systems specific to each train type. Most other Tube platforms are only 350ft.
The western part of the Circle Line has platforms too short to accommodate District Line D78 Stock.
The sub-surface lines were mostly constructed by the "cut-and-cover" method so generously proportioned, and can mostly take full sized rolling-stock.
Tube stocks are usually identified by the year in which delivery was scheduled, sub surface stock by a letter followed by two digits indicating the year of first deliveries.
'D' stock
The useful asset life of rolling stock is generally considered to be 40 years. Major refurbishment is estimated to be able to prolong the useful life by another 10-15 years and costs around one-sixth of the cost of a new train.
Units of ex London Underground 1938 rolling stock are still in service April 2002 on the Isle of Wight.
Further reading: Underground Train File - 1933-1959, by Brian Hardy. Published by Capital Transport 2001.
