London Underground with smaller trains that run in two circular tunnels ("tubes") with a diameter about . These lines have the exclusive use of a pair of tracks, except for the Piccadilly line, which shares track with the District line between Acton Town and Hanger Lane Junction and with the Metropolitan line between Rayners Lane and Uxbridge; and the Bakerloo line, which shares track with London Overground services north of Queen's Park. Fifty-five per cent of the system runs on the surface. There are of cut-and-cover tunnel and of tube tunnel. Many of the central London underground stations on deep-level tube routes
Safety on the London Underground Safety on the London Underground This article is primarily concerned with accidents on the London Underground network, which carries around a billion passengers a year. Statistically, there is just one fatal accident for every 300 million journeys. There are several safety warnings given to passengers, such as the traditional 'mind the gap' announcement and the regular announcements for passengers to keep behind the yellow line. Relatively few accidents are caused by overcrowding on the platforms, and staff monitor platforms and passageways at busy times preventing people entering the system if they become overcrowded. Most fatalities on the network are suicides.