The Moorgate tube crash occurred on 28 February 1975 on the isolated Northern City Line when a southbound train failed to stop at the Moorgate terminus and crashed into the wall at end of the tunnel, killing forty-four people. No fault was found with the train equipment, the subsequent report found that there was insufficient evidence 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.