Automatic Warning System
Encyclopedia
The Automatic Warning System (AWS) is a form of limited cab signalling
and train protection system introduced in 1956 in the United Kingdom
to help train drivers
observe and obey signals
. It was based on a 1930 system developed by Alfred Ernest Hudd and marketed as the "Strowger-Hudd" system. An earlier contact system, installed on the Great Western Railway
since 1906 and known as Automatic Train Control
(ATC), was gradually supplanted by AWS within the Western Region of British Railways
.
system and warns the driver about the aspect of the next signal. These warnings are normally given 200 yards (180 metres) before the signal. Information about the signal aspect is conveyed electromagnetically
to the moving train through equipment fixed in the middle of the track, known as AWS inductors. Each inductor contains a permanent magnet and an electromagnet which 'cancels' the effect of the permanent magnet. The system is fail-safe
because the electromagnet is required to be energised to give the 'clear' indication, the 'warning' indication being given by the permanent magnet alone.
When the AWS inductor is reached, the AWS sets a visual indicator in the driver's cab and gives an audible indication. If the signal being approached is displaying a 'clear' aspect, the AWS will sound a bell and leave the visual indicator black. This lets the driver know that the next signal is showing 'clear' and that the AWS system is working. If the signal being approached is displaying a restrictive aspect (red, yellow or double yellow), AWS will sound a horn continuously until the driver pushes a button to acknowledge it. The AWS will also give a warning horn on the approach to certain permanent speed restrictions and all temporary and emergency speed restrictions. When the warning is acknowledged, the horn stops and the visual indicator changes to a pattern of black and yellow spokes, which persists until the next AWS inductor and reminds the driver that they have cancelled the AWS and therefore have full responsibility for controlling the train. If the button is not pressed within six seconds, a full brake application brings the train to a halt. If the driver collapses onto the AWS cancel button, the system has a fail-safe mechanism built in, whereby it is not the press of the button that cancels the warning, it is when the driver lets go after the downward motion.
Early devices used a mechanical connection between the signal and the locomotive. In 1840, the locomotive engineer Edward Bury
experimented with a system whereby a lever at track level, connected to the signal, sounded the locomotive’s whistle and turned a cab-mounted red lamp. Ten years later, the redoubtable Colonel William Yolland
of the Railway Inspectorate was calling for a system that not only alerted the driver but also automatically applied the brakes when signals were passed at danger but no satisfactory method of bringing this about was found.
In 1873, United Kingdom Patent No. 3286 was granted to C. Davidson and C.D. Williams for a system in which, if a signal was passed at danger, a trackside lever operated the locomotive’s whistle, applied the brake, shut off steam and alerted the guard. Numerous similar patents followed but they all bore the same disadvantage – that they could not be used at higher speeds for risk of damage to the mechanism – and they came to nothing. In Germany, the Kofler system used arms projecting from signal posts to connect with a pair of levers, one representing caution and the other stop, mounted on the locomotive cab roof. To address the problem of operation at speed, the sprung mounting for the levers was connected directly to the locomotive's axle box to ensure correct alignment. When Berlin’s S-Bahn
was electrified in 1929, a development of this system, with the contact levers moved from the roofs to the sides of the trains, was installed at the same time.
The first useful device was invented by Vincent Raven
of the North Eastern Railway
in 1895, patent number 23384. Although this provided audible warning only, it did indicate to the driver when points ahead were set for a diverging route. By 1909, the company had installed it on about 100 miles of track.
and protected by UK patents 12661 and 25955. Its benefits over previous systems were that it could be used at high speed and that it sounded a confirmation in the cab when a signal was passed at 'clear'.
In the final version of the GWR system, the locomotives were fitted with a solenoid
-operated valve into the vacuum train pipe, maintained in the closed position by a battery. At each distant signal, a long ramp was placed between the rails. This ramp consisted of a metal blade set edge on, parallel to the rails, mounted on a wooden support. The ramp was curved with the highest point in the middle. As the locomotive passed over the ramp, a sprung contact shoe beneath the locomotive was lifted and the battery current holding closed the brake valve was broken. In the case of a clear signal, current from a battery energising the ramp (but at opposite polarity) passed to the locomotive through the contact and maintained the brake valve in the closed position, with the reversed-polarity current ringing a bell in the cab. When the signal was at 'danger', the ramp battery was disconnected and so could not replace the locomotive’s battery current: the brake valve solenoid would then be released and a horn sounded in the cab. The driver was then expected to cancel the warning and apply the brakes under his own control.
Notwithstanding the heavy commitment of maintaining the batteries in the locomotives and signal box
es, the GWR installed the equipment on all its main lines. For many years, Western Region
(successors to the GWR) locomotives were dual fitted with both GWR ATC and BR AWS system.
, were considering systems of their own. A non-contact method based on magnetic induction
was preferred, to eliminate the problems caused by snowfall and day-to-day wear of the contacts which had been discovered in existing systems. The Strowger-Hudd system of Alfred Hudd, which used a pair of magnets, one a permanent and one an electro-magnet, was tested by the Southern Railway, London and North Eastern Railway
and the London, Midland and Scottish Railway
but these trials came to nothing.
In 1948 Hudd, now working for the LMS, equipped the London, Tilbury and Southend line
, a division of the LMS, with his system. It was successful and British Rail
ways developed the mechanism further by providing a visual indication in the cab of the aspect of the last signal passed. In 1956, the Ministry of Transport evaluated the GWR, LTS and BR systems and selected the one developed by BR as standard for Britain's railways. This was in response to the Harrow and Wealdstone accident
in 1952.
The system works on a set/reset principle.
When the signal is at 'clear' or green ("off"), the electro-magnet is energised. As the train passes, the permanent magnet sets the system. A short time later, as the train moves forward, the electromagnet resets the system. Once so reset, a bell is sounded (a chime on newer stock) and the indicator is set to all black if it is not already so. No acknowledgement is required from the driver. The system must be reset within one second of being set, otherwise it behaves as for a caution indication.
When the distant signal is at 'caution' or yellow (on), the electro-magnet is de-energised. As the train passes, the permanent magnet sets the system. However, since the electro-magnet is de-energised, the system is not reset. After the one second delay within which the system can be reset, a horn warning is given until the driver acknowledges by pressing a plunger. If the driver fails to acknowledge the warning within 2.75 seconds, the brakes are automatically applied. If the driver does acknowledge the warning, the indicator disk changes to yellow and black, to remind the driver that he has acknowledged a warning. The yellow and black indication persists until the next signal and serves as a reminder between signals that the driver is proceeding under caution. The one second delay before the horn sounds allows the system to operate correctly down to speeds as low as 1.75 miles per hour. Below this speed, the caution horn warning will always be given, but it will be automatically cancelled when the electromagnet resets the system if the driver has not already done so. The display will indicate all black once the system resets.
The system is fail-safe
since, in the event of a loss of power, only the electro-magnet is affected and therefore all trains passing will receive a warning. The system suffers one drawback in that on single track lines, the track equipment will set the AWS system on a train travelling in the opposite direction from that for which the track equipment is intended but not reset it as the electromagnet is encountered before the permanent magnet. To overcome this, a suppressor magnet may be installed in place of an ordinary permanent magnet. When energised, its suppressing coil diverts the magnetic flux from the permanent magnet so that no warning is received on the train. The suppressor magnet is fail-safe since loss of power will cause it to act like an ordinary permanent magnet. A cheaper alternative is the installation of a lineside sign that notifies the driver to cancel and ignore the warning. This sign is a blue square board with a white St Andrew's cross on it (or a yellow board with a black cross, if provided in conjunction with a temporary speed restriction).
With mechanical signalling, the AWS system was installed only at distant signals but, with multi-aspect signalling, it is fitted at all main line signals. All signal aspects, except green, cause the horn to sound and the indicator disc to change to yellow on black.
AWS equipment without electromagnets are fitted at locations where a caution signal is invariably required or where a temporary caution is needed (for example, a temporary speed restriction). This is a secondary advantage of the system because temporary AWS equipment need only contain a permanent magnet. No electrical connection or supply is needed. In this case, the caution indication in the cab will persist until the next green signal is encountered.
AWS is an advisory system and can be easily overridden by habituated reactions of the driver, especially when they are proceeding at speed under a series of "double yellow" signals which indicate a signal at 'danger' two sections ahead. This has led to a number of fatal accidents. Also, there is no compulsory stop when a red signal is passed. The newer TPWS, which operates at certain stop signals and on the approach to some speed restrictions and buffer stops, overcomes some of these problems.
Cab signalling
Cab signalling is a railway safety system that communicates track status information to the cab, crew compartment or driver's compartment of a locomotive, railcar or multiple unit, where the train driver or engine driver can see the information....
and train protection system introduced in 1956 in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
to help train drivers
Railroad engineer
A railroad engineer, locomotive engineer, train operator, train driver or engine driver is a person who drives a train on a railroad...
observe and obey signals
Railway signal
A signal is a mechanical or electrical device erected beside a railway line to pass information relating to the state of the line ahead to train/engine drivers. The driver interprets the signal's indication and acts accordingly...
. It was based on a 1930 system developed by Alfred Ernest Hudd and marketed as the "Strowger-Hudd" system. An earlier contact system, installed on the Great Western Railway
Great Western Railway
The Great Western Railway was a British railway company that linked London with the south-west and west of England and most of Wales. It was founded in 1833, received its enabling Act of Parliament in 1835 and ran its first trains in 1838...
since 1906 and known as Automatic Train Control
Automatic Train Control
Automatic Train Control is a train protection system for railways, ensuring the safe and smooth operation of trains on ATC-enabled lines. Its main advantages include making possible the use of cab signalling instead of track-side signals and the use of smooth deceleration patterns in lieu of the...
(ATC), was gradually supplanted by AWS within the Western Region of British Railways
Western Region of British Railways
The Western Region was a region of British Railways from 1948. The region ceased to be an operating unit in its own right in the 1980s and was wound up at the end of 1992...
.
Principles of operation
AWS is part of the signallingRailway signalling
Railway signalling is a system used to control railway traffic safely, essentially to prevent trains from colliding. Being guided by fixed rails, trains are uniquely susceptible to collision; furthermore, trains cannot stop quickly, and frequently operate at speeds that do not enable them to stop...
system and warns the driver about the aspect of the next signal. These warnings are normally given 200 yards (180 metres) before the signal. Information about the signal aspect is conveyed electromagnetically
Electromagnetism
Electromagnetism is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation...
to the moving train through equipment fixed in the middle of the track, known as AWS inductors. Each inductor contains a permanent magnet and an electromagnet which 'cancels' the effect of the permanent magnet. The system is fail-safe
Fail-safe
A fail-safe or fail-secure device is one that, in the event of failure, responds in a way that will cause no harm, or at least a minimum of harm, to other devices or danger to personnel....
because the electromagnet is required to be energised to give the 'clear' indication, the 'warning' indication being given by the permanent magnet alone.
When the AWS inductor is reached, the AWS sets a visual indicator in the driver's cab and gives an audible indication. If the signal being approached is displaying a 'clear' aspect, the AWS will sound a bell and leave the visual indicator black. This lets the driver know that the next signal is showing 'clear' and that the AWS system is working. If the signal being approached is displaying a restrictive aspect (red, yellow or double yellow), AWS will sound a horn continuously until the driver pushes a button to acknowledge it. The AWS will also give a warning horn on the approach to certain permanent speed restrictions and all temporary and emergency speed restrictions. When the warning is acknowledged, the horn stops and the visual indicator changes to a pattern of black and yellow spokes, which persists until the next AWS inductor and reminds the driver that they have cancelled the AWS and therefore have full responsibility for controlling the train. If the button is not pressed within six seconds, a full brake application brings the train to a halt. If the driver collapses onto the AWS cancel button, the system has a fail-safe mechanism built in, whereby it is not the press of the button that cancels the warning, it is when the driver lets go after the downward motion.
Early devices
Bury, Curtis, and Kennedy
Bury, Curtis and Kennedy was a steam locomotive manufacturer in Liverpool, England.Edward Bury set up his works in 1826, under the name of Edward Bury and Company. He employed James Kennedy, who had gained experience of locomotive production under Robert Stephenson and Mather, Dixon and Company,...
experimented with a system whereby a lever at track level, connected to the signal, sounded the locomotive’s whistle and turned a cab-mounted red lamp. Ten years later, the redoubtable Colonel William Yolland
William Yolland
William Yolland CB, FRS was an English military surveyor, astronomer and engineer, and was Britain’s Chief Inspector of Railways from 1877 until his death...
of the Railway Inspectorate was calling for a system that not only alerted the driver but also automatically applied the brakes when signals were passed at danger but no satisfactory method of bringing this about was found.
In 1873, United Kingdom Patent No. 3286 was granted to C. Davidson and C.D. Williams for a system in which, if a signal was passed at danger, a trackside lever operated the locomotive’s whistle, applied the brake, shut off steam and alerted the guard. Numerous similar patents followed but they all bore the same disadvantage – that they could not be used at higher speeds for risk of damage to the mechanism – and they came to nothing. In Germany, the Kofler system used arms projecting from signal posts to connect with a pair of levers, one representing caution and the other stop, mounted on the locomotive cab roof. To address the problem of operation at speed, the sprung mounting for the levers was connected directly to the locomotive's axle box to ensure correct alignment. When Berlin’s S-Bahn
S-Bahn
S-Bahn refers to an often combined city center and suburban railway system metro in Austria, Germany, Switzerland and Denmark...
was electrified in 1929, a development of this system, with the contact levers moved from the roofs to the sides of the trains, was installed at the same time.
The first useful device was invented by Vincent Raven
Vincent Raven
Sir Vincent Litchfield Raven KBE was chief mechanical engineer of the North Eastern Railway from 1910 to 1922.- Biography :...
of the North Eastern Railway
North Eastern Railway (UK)
The North Eastern Railway , was an English railway company. It was incorporated in 1854, when four existing companies were combined, and was absorbed into the London and North Eastern Railway at the Grouping in 1923...
in 1895, patent number 23384. Although this provided audible warning only, it did indicate to the driver when points ahead were set for a diverging route. By 1909, the company had installed it on about 100 miles of track.
GWR Automatic Train Control
The first system to be put into wide use was developed in 1905 by the Great Western RailwayGreat Western Railway
The Great Western Railway was a British railway company that linked London with the south-west and west of England and most of Wales. It was founded in 1833, received its enabling Act of Parliament in 1835 and ran its first trains in 1838...
and protected by UK patents 12661 and 25955. Its benefits over previous systems were that it could be used at high speed and that it sounded a confirmation in the cab when a signal was passed at 'clear'.
In the final version of the GWR system, the locomotives were fitted with a solenoid
Solenoid
A solenoid is a coil wound into a tightly packed helix. In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. Solenoids are important because they can create...
-operated valve into the vacuum train pipe, maintained in the closed position by a battery. At each distant signal, a long ramp was placed between the rails. This ramp consisted of a metal blade set edge on, parallel to the rails, mounted on a wooden support. The ramp was curved with the highest point in the middle. As the locomotive passed over the ramp, a sprung contact shoe beneath the locomotive was lifted and the battery current holding closed the brake valve was broken. In the case of a clear signal, current from a battery energising the ramp (but at opposite polarity) passed to the locomotive through the contact and maintained the brake valve in the closed position, with the reversed-polarity current ringing a bell in the cab. When the signal was at 'danger', the ramp battery was disconnected and so could not replace the locomotive’s battery current: the brake valve solenoid would then be released and a horn sounded in the cab. The driver was then expected to cancel the warning and apply the brakes under his own control.
Notwithstanding the heavy commitment of maintaining the batteries in the locomotives and signal box
Signal box
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...
es, the GWR installed the equipment on all its main lines. For many years, Western Region
Western Region of British Railways
The Western Region was a region of British Railways from 1948. The region ceased to be an operating unit in its own right in the 1980s and was wound up at the end of 1992...
(successors to the GWR) locomotives were dual fitted with both GWR ATC and BR AWS system.
Strowger-Hudd system
By the 1930s, other railway companies, under pressure from the Ministry of TransportDepartment for Transport
In the United Kingdom, the Department for Transport is the government department responsible for the English transport network and a limited number of transport matters in Scotland, Wales and Northern Ireland which are not devolved...
, were considering systems of their own. A non-contact method based on magnetic induction
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
was preferred, to eliminate the problems caused by snowfall and day-to-day wear of the contacts which had been discovered in existing systems. The Strowger-Hudd system of Alfred Hudd, which used a pair of magnets, one a permanent and one an electro-magnet, was tested by the Southern Railway, London and North Eastern Railway
London and North Eastern Railway
The London and North Eastern Railway was the second-largest of the "Big Four" railway companies created by the Railways Act 1921 in Britain...
and the London, Midland and Scottish Railway
London, Midland and Scottish Railway
The London Midland and Scottish Railway was a British railway company. It was formed on 1 January 1923 under the Railways Act of 1921, which required the grouping of over 120 separate railway companies into just four...
but these trials came to nothing.
In 1948 Hudd, now working for the LMS, equipped the London, Tilbury and Southend line
London, Tilbury and Southend Railway
The London, Tilbury and Southend Railway is an English railway line linking Fenchurch Street railway station in the City of London with northeast London and the entire length of the northern Thames Gateway area of southern Essex. It is currently known as the Essex Thameside Route by Network Rail...
, a division of the LMS, with his system. It was successful and British Rail
British Rail
British Railways , which from 1965 traded as British Rail, was the operator of most of the rail transport in Great Britain between 1948 and 1997. It was formed from the nationalisation of the "Big Four" British railway companies and lasted until the gradual privatisation of British Rail, in stages...
ways developed the mechanism further by providing a visual indication in the cab of the aspect of the last signal passed. In 1956, the Ministry of Transport evaluated the GWR, LTS and BR systems and selected the one developed by BR as standard for Britain's railways. This was in response to the Harrow and Wealdstone accident
Harrow and Wealdstone rail crash
The Harrow and Wealdstone rail crash was a major railway disaster and collision on the British railway system on 8 October 1952.The accident took place from central London...
in 1952.
British Rail AWS
BR AWS consists of:- a permanent magnet set centrally between the rails and usually positioned such that it is encountered before the signal to which it relates.
- an electro-magnet between the rails (with opposite polarity to the permanent magnet) positioned after the permanent magnet.
- a cab indicator that can show a black disk or a yellow and black "exploding" disk, known as the "AWS sunflower".
- a control unit that connects the system to the brakes on the train.
- a driver's AWS acknowledgement button.
- an AWS control panel.
The system works on a set/reset principle.
When the signal is at 'clear' or green ("off"), the electro-magnet is energised. As the train passes, the permanent magnet sets the system. A short time later, as the train moves forward, the electromagnet resets the system. Once so reset, a bell is sounded (a chime on newer stock) and the indicator is set to all black if it is not already so. No acknowledgement is required from the driver. The system must be reset within one second of being set, otherwise it behaves as for a caution indication.
The system is fail-safe
Fail-safe
A fail-safe or fail-secure device is one that, in the event of failure, responds in a way that will cause no harm, or at least a minimum of harm, to other devices or danger to personnel....
since, in the event of a loss of power, only the electro-magnet is affected and therefore all trains passing will receive a warning. The system suffers one drawback in that on single track lines, the track equipment will set the AWS system on a train travelling in the opposite direction from that for which the track equipment is intended but not reset it as the electromagnet is encountered before the permanent magnet. To overcome this, a suppressor magnet may be installed in place of an ordinary permanent magnet. When energised, its suppressing coil diverts the magnetic flux from the permanent magnet so that no warning is received on the train. The suppressor magnet is fail-safe since loss of power will cause it to act like an ordinary permanent magnet. A cheaper alternative is the installation of a lineside sign that notifies the driver to cancel and ignore the warning. This sign is a blue square board with a white St Andrew's cross on it (or a yellow board with a black cross, if provided in conjunction with a temporary speed restriction).
With mechanical signalling, the AWS system was installed only at distant signals but, with multi-aspect signalling, it is fitted at all main line signals. All signal aspects, except green, cause the horn to sound and the indicator disc to change to yellow on black.
AWS equipment without electromagnets are fitted at locations where a caution signal is invariably required or where a temporary caution is needed (for example, a temporary speed restriction). This is a secondary advantage of the system because temporary AWS equipment need only contain a permanent magnet. No electrical connection or supply is needed. In this case, the caution indication in the cab will persist until the next green signal is encountered.
Expansion of AWS application
- From 1971, AWS permanent magnets would be fitted at the advance warning boards installed on the approach to severe permanent speed restrictions. This was a recommendation of the inquiry into the derailment at Morpeth on 7 May 1969.
- From 1977, portable AWS permanent magnets would be fitted at the warning boards on the approach to temporary speed restrictions (TSRs). This was a recommendation of the inquiry into the derailment at NuneatonNuneaton rail crashThe Nuneaton rail crash was a train crash which occurred on 6 June 1975, on the West Coast Main Line just south of Nuneaton railway station in Warwickshire, England....
on 6 June 1975, which occurred when the driver missed a TSR warning board due to its lights being extinguished.
- From 1990, AWS permanent magnets were being installed immediately ahead of certain 'high risk' stop signals, as a SPADSignal passed at dangerA Signal passed at danger , in British railway terminology, occurs when a train passes a stop signal without authority to do so. It is a term primarily used within the British Railway Industry, although it can be applied worldwide.-Categories of SPAD:...
mitigation measure. This additional AWS magnet was suppressed when the associated signal showed a 'proceed' aspect. It is no longer current practice to use AWS for this purpose.
Disadvantages
Because it was developed before multiple-aspect signalling became widespread, AWS can only indicate whether a signal is "Green" or "not Green". Even though a multiple-aspect signal can display three or four aspects, AWS has only two states.AWS is an advisory system and can be easily overridden by habituated reactions of the driver, especially when they are proceeding at speed under a series of "double yellow" signals which indicate a signal at 'danger' two sections ahead. This has led to a number of fatal accidents. Also, there is no compulsory stop when a red signal is passed. The newer TPWS, which operates at certain stop signals and on the approach to some speed restrictions and buffer stops, overcomes some of these problems.
Two way tracks
Because the permanent magnet is located in the centre of the track, it operates in both direction, the reverse direction of which is not needed. Therefore the permanent magnetic has to be suppressed by an electric coil of suitable strength.Liberia
One of the mining railways in this country had a more advanced AWS system that employed two or three magnets of either polarity and located near the rails to avoid the suppression problem. The system was therefore about to give more aspects than the BR version.Use overseas
The BR AWS system is also used in- Northern IrelandNorthern IrelandNorthern Ireland is one of the four countries of the United Kingdom. Situated in the north-east of the island of Ireland, it shares a border with the Republic of Ireland to the south and west...
- Hong KongHong KongHong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...
, MTRMTRMass Transit Railway is the rapid transit railway system in Hong Kong. Originally opened in 1979, the system now includes 211.6 km of rail with 155 stations, including 86 railway stations and 69 light rail stops...
East Rail Line (Discontinued in 1998, trains now use TBL as of 2009, enhanced with ATPAutomatic Train ProtectionAutomatic Train Protection in Great Britain refers to either of two implementations of a train protection system installed in some trains in order to help prevent collisions through a driver's failure to observe a signal or speed restriction...
) - QueenslandQueenslandQueensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
, AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
; sometimes enhanced with ATPAutomatic Train ProtectionAutomatic Train Protection in Great Britain refers to either of two implementations of a train protection system installed in some trains in order to help prevent collisions through a driver's failure to observe a signal or speed restriction...
. At the other extreme Queensland also provides a permanent magnet at the fixed distant signal of unattended crossing loops. - AdelaideAdelaideAdelaide is the capital city of South Australia and the fifth-largest city in Australia. Adelaide has an estimated population of more than 1.2 million...
, South AustraliaSouth AustraliaSouth Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories.South Australia shares borders with all of the mainland...
See also
- Automatic Train ProtectionAutomatic Train ProtectionAutomatic Train Protection in Great Britain refers to either of two implementations of a train protection system installed in some trains in order to help prevent collisions through a driver's failure to observe a signal or speed restriction...
- Anti Collision Device - India
- Continuous Automatic Warning SystemContinuous Automatic Warning SystemThe Continuous Automatic Warning System is a form of cab signalling and train protection system used in Ireland to help train drivers observe and obey lineside signals....
- Driver reminder applianceDriver reminder applianceThe Driver's Reminder Appliance is a manual switch in the driving cab of a passenger train. When operated it glows bright red and prevents the driver from being able to take power...
- introduced in 1990s. - Train Protection & Warning System (TPWS)
- Train stopTrain stopPart of a railway signalling system, a train stop or trip stop 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.- Basic operation :The...
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