History of the London Underground to determine the cause. Following the incident, a system that stops a train automatically if the driver fails to brake was introduced at dead-ends on the London Underground. The Northern City Line was connected to British Rail tracks at Finsbury Park in the 1970s. The last tube train ran in October 1975, and British Rail services began in 1976. In 1977, the Piccadilly line was extended from Hounslow to Heathrow Airport, and in 1986 a platform serving Terminal 4 opened on a loop line. The Fleet line through central London was first proposed in 1965, taking over the Bakerloo line's
History of the London Underground line, took over part of the Bakerloo line; it was extended through the Docklands to Stratford in 1999. Under the control of the Greater London Council, London Transport introduced in 1981 a system of fare zones for buses and underground trains that cut the average fare. Fares increased following a legal challenge but the fare zones were retained, and in the mid-1980s the Travelcard and the Capitalcard were introduced. In the early years of the 21st century, London Underground was reorganised in a public–private partnership where private companies upgraded and maintained the infrastructure. In 2003 control passed to Transport for