On a rail transport system, signalling control is the process by which control is exercised over train movements by way of railway signals and block systems to ensure that trains operate safely, over the correct route and to the proper timetable. Signalling control was originally exercised via a decentralised network of control points that were known by a variety of names including signal box, interlocking tower and signal cabin. Currently these decentralised systems are being consolidated into wide scale signalling centres or dispatch offices. Whatever the form, signalling control provides an interface between the human signal operator and the lineside signalling equipment. The technical apparatus used to control switches (points), signals and block systems is called interlocking.
Railway signalling (BE), also called railroad signaling (AE), is a system used to control the movement of railway traffic. Trains move on fixed rails, making them uniquely susceptible to collision. This susceptibility is exacerbated by the enormous weight and inertia of a train, which makes it difficult to quickly stop when encountering an obstacle. In the UK, the Regulation of Railways Act 1889 introduced a series of requirements on matters such as the implementation of interlocked block signalling and other safety measures as a direct result of the Armagh rail disaster in that year.
In railway signalling, an interlocking is an arrangement of signal apparatus that prevents conflicting movements through an arrangement of tracks such as junctions or crossings. In North America, a set of signalling appliances and tracks interlocked together are sometimes collectively referred to as an interlocking plant or just as an interlocking. An interlocking system is designed so that it is impossible to display a signal to proceed unless the route to be used is proven safe.
The Automatic Warning System (AWS) provides a train driver with an audible indication of whether the next signal they are approaching is clear or at caution. Depending on the upcoming signal state, the AWS will either produce a 'horn' sound, or a 'bell' sound. If the train driver fails to acknowledge a warning indication, an emergency brake application is initiated by the AWS. However if the driver correctly acknowledges the warning indication by pressing an acknowledgement button, then a visual 'sunflower' is displayed to the driver, as a reminder of the warning.
Part of a railway signalling system, a train stop, trip stop or tripcock is a train protection device that automatically stops a train if it attempts to pass a signal when the signal aspect and operating rules prohibit such movement, or if it attempts to pass at an excessive speed.
The Hawes Junction rail crash occurred at 5.49 am on 24 December 1910, just north of Lunds Viaduct between Hawes Junction and Aisgill on the Midland Railway's Settle and Carlisle main line in the North Riding of Yorkshire, England. It was caused when a busy signalman, Alfred Sutton, forgot about a pair of light engines waiting at his down (northbound) starting signal to return to their shed at Carlisle. They were still waiting there when the signalman set the road for the down Scotch express. When the signal cleared, the light engines set off in front of the express into the same block section. Since the light engines were travelling at low speed from a stand at Hawes Junction, and the following express was travelling at high speed, a collision was inevitable. The express caught the light engines just after Moorcock Tunnel near Aisgill summit in Mallerstang and was almost wholly derailed.
The Cowan rail accident occurred at 7:20pm on 6 May 1990 when the 3801 Limited special steam passenger train returning from the Morpeth Jazz Festival was struck in the rear by the following CityRail inter-urban passenger service. The steam train had stalled while attempting to climb the steep gradient from the Hawkesbury River to Cowan, New South Wales, and it was found that sand applied to the rails to regain traction had interfered with the signals and given the following train a false clear indication.
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.
A defect detector is a device used on railroads to detect axle and signal problems in passing trains. The detectors are normally integrated into the tracks and often include sensors to detect several different kinds of problems that could occur. Defect detectors were one of the inventions which enabled American railroads to eliminate the caboose at the rear of the train, as well as various station agents placed along active routes to detect unsafe conditions. The use of defect detectors has since spread overseas to other railroad systems.
Over the latter years of the 19th and early years of the 20th centuries, Penistone in Yorkshire gained a name as an accident black-spot on Britain's railway network; indeed, it could be said to hold the title of the worst accident black-spot in the country. The main line through the town was the Woodhead route of the Manchester, Sheffield and Lincolnshire Railway between Sheffield Victoria and Manchester, London Road. The line was heavily graded with a summit some 400 yards inside the eastern portal of the Woodhead tunnel.
The Clayton Tunnel rail crash occurred on Sunday 25 August 1861, five miles (8 km) from Brighton on the south coast of England. At the time it was the worst accident on the British railway system. A train ran into the back of another inside the tunnel, killing 23 and injuring 176 passengers.
An axle counter is a system used in railway signalling to detect the clear or occupied status of a section of track between two points. The system generally consists of a wheel sensor and an evaluation unit for counting the axles of the train both into and out of the section. They are often used to replace a track circuit.
Clayton Tunnel is a railway tunnel located near the villages of Clayton and Pyecombe in West Sussex, between Hassocks and Preston Park railway stations on the Brighton Main Line. This tunnel is notable for its turreted and castellated north portal with a single-storey cottage on the top, as well as for being the site of a serious accident in 1861 which was influential in the adoption of a robust signalling system in the UK and elsewhere.
On 7 December 1991, two trains collided inside the Severn Tunnel, between England and Wales. There were no fatalities but 185 passengers were injured.
The Connington South rail crash occurred on 5 March 1967 on the East Coast Main Line near the village of Conington, Huntingdonshire, England. Five passengers were killed and 18 were injured.
Automatic block signaling (ABS), spelled automatic block signalling or called track circuit block (TCB) in the UK, is a railroad communications system that consists of a series of signals that divide a railway line into a series of sections, called blocks. The system controls the movement of trains between the blocks using automatic signals. ABS operation is designed to allow trains operating in the same direction to follow each other in a safe manner without risk of rear-end collision.
The Battersea Park rail crash occurred on 2 April 1937, just south of Battersea Park railway station on the Southern Railway, in London, England. Two electrically driven passenger trains collided on the Up Local line; the second train, from Coulsdon North to Victoria, had been allowed into the section while it was still occupied by the first train, from London Bridge to Victoria. The signalman at Battersea Park, G. F. Childs, believing there was a fault with the Sykes electromechanical interlocking apparatus which was installed at the box, had opened up the case of the instrument and inadvertently cleared the interlock which should have prevented this situation. The official enquiry ruled that he subsequently accepted the Coulsdon train, although he should have been aware that the London Bridge train had not cleared the section. Ten people were killed, including the guard of the London Bridge train, and eighty people were injured, seven sustaining serious injuries. Another accident had occurred at Battersea Park in 1881.
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.
Level crossing signals are the electronic warning devices for road vehicles at railroad level crossings.
There are around 6,000 level crossings in the United Kingdom, of which about 1,500 are public highway crossings. This number is gradually being reduced as the risk of accidents at level crossings is considered high. The director of the UK Railway Inspectorate commented in 2004 that "the use of level crossings contributes the greatest potential for catastrophic risk on the railways." The creation of new level crossings on the national network is banned, with bridges and tunnels being the more favoured options. The cost of making significant reductions, other than by simply closing the crossings, is substantial; some commentators argue that the money could be better spent. Some 5,000 crossings are user-worked crossings or footpaths with very low usage. The removal of crossings can improve train performance and lower accident rates, as some crossings have low rail speed limits enforced on them to protect road users. In fact, between 1845 and 1933, there was a 4 miles per hour (6.4 km/h) speed limit on level crossings of turnpike roads adjacent to stations for lines whose authorising Act of Parliament had been consolidated in the Railways Clauses Consolidation Act 1845 although this limit was at least sometimes disregarded.
