London Underground D78 Stock London Underground D78 Stock The London Underground D78 Stock, commonly referred to as D Stock, was a type of sub-surface rolling stock which operated on the District line of the London Underground, except on the Wimbledon to Edgware Road service. Following the withdrawal of the C Stock in June 2014, these were the oldest subsurface trains in service on the London Underground. The first units were withdrawn in January 2015 with the last withdrawn on 21 April 2017. The D stock was ordered in 1976 to replace the pre-war CO/CP Stock and post-war R Stock on the District line. Seventy-five
London Underground rolling stock numbering and classification London Underground rolling stock numbering and classification Rolling stock used on the London Underground and its constituent companies has been classified using a number of different schemes. This page explains the principal systems. The numbering and classification of electric multiple unit stock on the London Underground is usually related to the type of line that the trains are used on. There are two distinct types of line: 'Sub-surface' lines (earlier lines built on the cut-and-cover method, which use trains of similar size to those on the national railway network), and 'Tube' lines (deep-level lines, built to a more restricted size).