District line Railway (L&SWR), and branches reached Ealing Broadway, Hounslow and Wimbledon. As part of the project that completed the Circle line in October 1884, the District began to serve Whitechapel. Services began running to Upminster in 1902, after a link to the London, Tilbury & Southend Railway (LT&SR) had been built. At the start of the 20th century the District was seeing increased competition from the new electric underground tube lines and trams, and the use of steam locomotives underground led to unpopular smoke-filled stations and carriages. The American Charles Yerkes, who was later to form the Underground Electric Railways of
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).