In the early 1970s London Transport placed an order for a new fleet of trains to replace the 1959 stock, the 1938 stock and 1962 stock vehicles which previously operated on the Piccadilly line. Built between 1974 and 1977 by Metro Cammell in Birmingham, the first unit entered service on 19 July 1975 and the last was introduced by 1977. The trains featured longer cars and larger door space than the previous units, being designed for airport travellers with luggage. The order was for 87½ 6-car trains, made up of 196 Driving Motor cars, 175 Trailer cars and 154 Uncoupling Non-Driving Motor cars. Each train is made up of two 3-car units, and most units are single-ended, formed DM-T-UNDM. There are also 21 double-ended units, formed DM-T-DM, to provide additional flexibility and to operate the Aldwych shuttle. The initial order additionally included two test units equipped with solid state traction equipment and electronic control systems. These were double-ended units 892-692-893 and 894-694-895, and were known collectively as the ETT. The first unit was equipped by Westinghouse, the second by GEC. In order to provide additional units for the opening of the Heathrow loop, these units were converted to standard at Acton Works, entering service between 1986 and 1987. One three-car unit was damaged in a terrorist attack on 7 July 2005 and subsequently scrapped.
Refurbishment
From 1996 to 2001, the entire fleet was refurbished by Bombardier Transportation in Horbury, Wakefield. The interior was completely remodelled, with changes including the removal of transverse seating, replacement of the original wooden flooring with new floor material, replacement of straphangers with new grab rails, new enclosures for the ceiling ventilation fans, brighter lighting with new diffusers, installation of car-end windows and new perch seats in the centre of the cars, creating more luggage space for airport passengers. The original unpainted exterior was painted in London Underground's corporate livery, and a new emergency detrainment system was fitted in the cabs. The external destination blinds were also replaced with LCD displays, and these were subsequently replaced with new LED units in 2015. The final refurbished unit re-entered service on 10 July 2001.
Future replacement
The Deep tube programme originally covered the replacement of the trains and signalling on the Bakerloo and Piccadilly lines, and had been expanded to cover rolling stock requirements arising from the planned extension of the Northern line to Battersea, the eventual replacement of Central line trains and proposed increased service frequency on the Northern and Jubilee lines. The EVO tube concept design, a lighter articulated train with walk through cars, was introduced early in 2011. In early 2014 the Bakerloo, Piccadilly, Central and Waterloo & City line rolling stock replacement project was renamed New Tube for London and moved from its feasibility stage to the design and specification stage. The proposal introduces fully automated trains and signalling to increase capacity first on the Piccadilly line in 2025, followed the Central, Waterloo & City, and Bakerloo lines by 2033. The fully automated trains may not have drivers, however the ASLEF and RMTtrade unions that represent the drivers strongly oppose this, saying it would be unsafe. In June 2018, TfL announced 94 six-car Siemens Inspiro trains are to replace the 1973 Stock between 2023 and 2026.
