In engineering, a fail-safe is a design feature or practice that, in the event of a failure of the design feature, inherently responds in a way that will cause minimal or no harm to other equipment, to the environment or to people. Unlike inherent safety to a particular hazard, a system being "fail-safe" does not mean that failure is naturally inconsequential, but rather that the system's design prevents or mitigates unsafe consequences of the system's failure. If and when a "fail-safe" system fails, it remains at least as safe as it was before the failure. Since many types of failure are possible, failure mode and effects analysis is used to examine failure situations and recommend safety design and procedures.
Embankment is a London Underground station in the City of Westminster, known by various names during its history. It is served by the Bakerloo, Circle, District and Northern lines. On the Bakerloo line and the Charing Cross branch of the Northern line, the station is between Charing Cross and Waterloo stations. On the Circle and District lines, it is between Westminster and Temple stations. It is located in Travelcard Zone 1. The station has two entrances, one on Victoria Embankment and the other on Villiers Street. The station is adjacent to Victoria Embankment Gardens and is close to Charing Cross station, Embankment Pier, Hungerford Bridge, Cleopatra's Needle, the Royal Air Force Memorial, the Savoy Chapel and Savoy Hotel and the Playhouse and New Players Theatres.
A signal passed at danger (SPAD), known in the United States as a stop signal overrun (SSO) and in Canada as passing a stop signal, is an event on a railway where a train passes a stop signal without authority. This is also known as running a red.
Double switching, double cutting, or double breaking is the practice of using a multipole switch to close or open both the positive and negative sides of a DC electrical circuit, or both the hot and neutral sides of an AC circuit. This technique is used to prevent shock hazard in electric devices connected with unpolarised AC power plugs and sockets. Double switching is a crucial safety engineering practice in railway signalling, wherein it is used to ensure that a single false feed of current to a relay is unlikely to cause a wrong-side failure. It is an example of using redundancy to increase safety and reduce the likelihood of failure, analogous to double insulation. Double switching increases the cost and complexity of systems in which it is employed, for example by extra relay contacts and extra relays, so the technique is applied selectively where it can provide a cost-effective safety improvement.
The Clapham Junction rail crash occurred on the morning of 12 December 1988, when a crowded British Rail passenger train crashed into the rear of another train that had stopped at a signal just south of Clapham Junction railway station in London, England, and subsequently sideswiped an empty train travelling in the opposite direction. A total of 35 people died in the collision, while 484 were injured.
A wrong-side failure describes a failure condition in a piece of railway signalling equipment that results in an unsafe state. A typical example would be a signal showing a 'proceed' aspect when it should be showing a 'stop' or 'danger' aspect, resulting in a "false clear".
The Purley station rail crash was a train collision that occurred just to the north of Purley railway station in the London Borough of Croydon on Saturday 4 March 1989, leaving five dead and 88 injured. The collision was caused by the driver of one of the trains passing a signal at danger; he pleaded guilty to manslaughter and was sentenced to 12 months in prison plus six months suspended, although this was reduced to four months upon appeal, and in 2007 overturned. The Department of Transport report noted that the signal had a high incidence of being passed at danger and recommended that an automatic train protection system should be introduced without delay and in the interim a repeater for the signal that had been passed be installed.
A track circuit is an electrical device used to prove the absence of a train on rail tracks to signallers and control relevant signals. An alternative to track circuits are axle counters.
The Harrow and Wealdstone rail crash was a three-train collision at Harrow and Wealdstone station in Wealdstone, Middlesex during the morning rush hour of 8 October 1952. The crash resulted in 112 deaths and 340 injuries, 88 of these being detained in hospital. It remains the worst peacetime rail crash in British history and the second deadliest overall after the Quintinshill rail disaster of 1915.
The Gaisal train collision occurred on 2 August 1999, when two trains carrying about 2,500 people collided at the remote station of Gaisal in West Bengal, India. Owing to a signalling error, both trains were using the same track on a day when three of the four tracks on the line were closed for maintenance. Their combined speeds were so great that the trains exploded on impact, killing at least 285 people.
Two rail accidents have occurred near Castlecary, Scotland. One of these was in 1937 and one in 1968. Both events involved rear-end collisions, and caused the deaths of 35 and 2 people respectively.
The Cowden rail crash occurred on 15 October 1994, near Cowden Station in Kent (UK), when two trains collided head-on, killing five and injuring thirteen, after one of them had passed a signal at danger and entered a single-line section. The cause was driver error, possibly involving a guard who was in the cabin against regulations.
The Spa Road Junction rail crash was an accident on the British railway system which occurred during the peak evening rush hour of 8 January 1999 at Spa Road Junction in Bermondsey, in South East London.
The Barnes rail crash, in which 13 people were killed and 41 were injured, occurred at Barnes railway station late in the evening of Friday 2 December 1955.
The Charing Cross tube crash occurred at 08:32 hours on 10 March 1938, when a Northern line train ran into the rear of a stationary train near Charing Cross in London. Twelve people were slightly injured. The accident was caused by a signal technician carrying out a temporary repair to a faulty signal even though he was not familiar with the layout and did not have access to the signalling diagram.
The Wrawby Junction rail crash was a train crash which occurred on 9 December 1983, at Wrawby Junction, near Barnetby station, North Lincolnshire, England.
During the afternoon rush hour of June 22, 2009, a subway train wreck occurred between two southbound Red Line Washington Metro trains in Northeast, Washington, D.C., United States. A moving train collided with a train stopped ahead of it; the train operator along with eight passengers died, and 80 people were injured, making it the deadliest crash in the history of the Washington Metro.
The Marden rail crash occurred on 4 January 1969 near Marden, Kent, United Kingdom, when a passenger train ran into the rear of a parcels train, having passed two signals at danger. Four people were killed and 11 were injured. One person was awarded the British Empire Medal for his part in the aftermath of the collision.
On 3 February 2003, a Comeng electric multiple unit train rolled away from Broadmeadows station in Melbourne, Australia, before it ran for nearly 17 kilometres (11 mi) out of control without a driver and eventually crashed into another train about to depart Spencer Street station. Train controllers attempted several times to stop or redirect the train, but were limited in their ability to intervene, instead being forced to alter the route of other trains to avert a more serious collision. Eleven people on board the stationary train were injured; authorities did not know until after the crash if any passengers were on board the runaway. An investigation identified driver error as the cause of the accident, but the runaway event prompted significant debate about the role of government authorities and private operators in ensuring safety and reliability on the Melbourne rail network.
On the evening of 26 December 1962, cold weather and snow in and around Crewe had caused points to become frozen and trains were being detained at signals. About midway between Winsford and Crewe, the 13:30 Glasgow Central to London Euston Mid-Day Scot, hauled by an English Electric type 4 diesel, D215, with 13 coaches and 500 passengers, was stopped at a signal but the driver found the telephone to Coppenhall Junction, the next signal box ahead, out of order. Seeing the next signal ahead he decided to proceed down towards it and use the telephone there, but too fast. In the darkness he failed to notice the 16:45 express from Liverpool Lime Street to Birmingham New Street, hauled by an electric locomotive with eight coaches with 300 passengers, standing on the line ahead and collided with it at about 20 mph (32 km/h).
