1.
Midland Railway
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The Midland Railway was a railway company in the United Kingdom from 1844 to 1922, when it became part of the London, Midland and Scottish Railway. It had a network of lines managed from its headquarters in Derby. It became the third-largest railway undertaking in the British Isles, the Midland Railway Consolidation Act was passed in 1844 authorising the merger of the Midland Counties Railway, the North Midland Railway, and the Birmingham and Derby Junction Railway. These met at the Tri-Junct station at Derby, where the MR established its locomotive and later its carriage, leading it were George Hudson from the North Midland, dynamic but unscrupulous, and John Ellis from the Midland Counties, a careful businessman of impeccable integrity. James Allport from the Birmingham and Derby Junction Railway found a place elsewhere in Hudsons empire with the York, Newcastle and Berwick Railway, though he later returned. Almost immediately it took over the Sheffield and Rotherham Railway and the Erewash Valley Line in 1845, passengers from Sheffield continued to use Rotherham Masborough until a direct route was completed in 1870. Meanwhile, it extended its influence in the Leicestershire coalfields, by buying the Leicester and Swannington Railway in 1846, after the merger, London trains were carried on the shorter Midland Counties route. The former Birmingham and Derby Junction Railway was left with the traffic to Birmingham and Bristol, the line south was the Birmingham and Bristol Railway, which reached Curzon Street via Camp Hill. These two lines had been formed by the merger of the standard gauge Birmingham and Gloucester Railway and they met at Gloucester via a short loop of the Cheltenham and Great Western Union Railway. In the event all that was necessary was for the later LNWR to share Birmingham New Street with the Midland when it was opened in 1854, the MR controlled all the traffic to the North East and Scotland from London. The LNWR was progressing slowly through the Lake District, and there was pressure for a line from London to York. Permission had been gained for the Northern and Eastern Railway to run through Peterborough and Lincoln, two obvious extensions of the Midland Counties line were from Nottingham to Lincoln and from Leicester to Peterborough. They were approved while the bill for the line was still before Parliament, forming the present day Lincoln Branch. The Leeds and Bradford Railway had been approved in 1844, by 1850 it was losing money but a number of railways offered to buy it. In spite of the objections of Hudson, for the MR and others, the London and York Railway led by Edmund Denison persisted, after Hudsons departure, the MR was in financial difficulties. Opposition to the Great Northern bill had cost a fortune, a deal of maintenance was overdue. Added to this, the Great Northern was taking much of the traffic from the North East, in 1851 the Ambergate, Nottingham, Boston and Eastern Junction Railway completed its line from Grantham as far as Colwick, from where a branch led to the MR Nottingham station. The Great Northern Railway by then passed through Grantham and both railway companies paid court to the fledgling line, meanwhile, Nottingham had woken up to its branch line status and was keen to expand
2.
Rail transport
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Rail transport is a means of conveyance of passengers and goods on wheeled vehicles running on rails, also known as tracks. It is also referred to as train transport. In contrast to road transport, where vehicles run on a flat surface. Tracks usually consist of rails, installed on ties and ballast, on which the rolling stock, usually fitted with metal wheels. Other variations are possible, such as slab track, where the rails are fastened to a concrete foundation resting on a prepared subsurface. Rolling stock in a transport system generally encounters lower frictional resistance than road vehicles, so passenger. The operation is carried out by a company, providing transport between train stations or freight customer facilities. Power is provided by locomotives which either draw electric power from a railway system or produce their own power. Most tracks are accompanied by a signalling system, Railways are a safe land transport system when compared to other forms of transport. The oldest, man-hauled railways date back to the 6th century BC, with Periander, one of the Seven Sages of Greece, Rail transport blossomed after the British development of the steam locomotive as a viable source of power in the 19th centuries. With steam engines, one could construct mainline railways, which were a key component of the Industrial Revolution, also, railways reduced the costs of shipping, and allowed for fewer lost goods, compared with water transport, which faced occasional sinking of ships. The change from canals to railways allowed for markets in which prices varied very little from city to city. In the 1880s, electrified trains were introduced, and also the first tramways, starting during the 1940s, the non-electrified railways in most countries had their steam locomotives replaced by diesel-electric locomotives, with the process being almost complete by 2000. During the 1960s, electrified high-speed railway systems were introduced in Japan, other forms of guided ground transport outside the traditional railway definitions, such as monorail or maglev, have been tried but have seen limited use. The history of the growth, decline and restoration to use of transport can be divided up into several discrete periods defined by the principal means of motive power used. The earliest evidence of a railway was a 6-kilometre Diolkos wagonway, trucks pushed by slaves ran in grooves in limestone, which provided the track element. The Diolkos operated for over 600 years, Railways began reappearing in Europe after the Dark Ages. The earliest known record of a railway in Europe from this period is a window in the Minster of Freiburg im Breisgau in Germany
3.
Train station
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A train station, railway station, railroad station, or depot is a railway facility where trains regularly stop to load or unload passengers or freight. It generally consists of at least one platform and a station building providing such ancillary services as ticket sales. If a station is on a line, it often has a passing loop to facilitate traffic movements. The smallest stations are most often referred to as stops or, in parts of the world. Stations may be at level, underground, or elevated. Connections may be available to intersecting rail lines or other modes such as buses. In British usage, the station is commonly understood to mean a railway station unless otherwise qualified. In the United States, the most common term in contemporary usage is train station, Railway station and railroad station are less frequent. Outside North America, a depot is place where buses, trains, or other vehicles are housed and maintained and from which they are dispatched for service. The two-storey Mount Clare station in Baltimore, Maryland, which survives as a museum, first saw service as the terminus of the horse-drawn Baltimore. The oldest terminal station in the world was Crown Street railway station in Liverpool, built in 1830, as the first train on the Liverpool-Manchester line left Liverpool, the station is slightly older than the Manchester terminal at Liverpool Road. The station was the first to incorporate a train shed, the station was demolished in 1836 as the Liverpool terminal station moved to Lime Street railway station. Crown Street station was converted to a goods station terminal, the first stations had little in the way of buildings or amenities. The first stations in the modern sense were on the Liverpool and Manchester Railway, manchesters Liverpool Road Station, the second oldest terminal station in the world, is preserved as part of the Museum of Science and Industry in Manchester. It resembles a row of Georgian houses, dual-purpose stations can sometimes still be found today, though in many cases goods facilities are restricted to major stations. In rural and remote communities across Canada and the United States, such stations were known as flag stops or flag stations. Many stations date from the 19th century and reflect the architecture of the time. Countries where railways arrived later may still have such architecture, as later stations often imitated 19th-century styles, various forms of architecture have been used in the construction of stations, from those boasting grand, intricate, Baroque- or Gothic-style edifices, to plainer utilitarian or modernist styles
4.
Railway signal
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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 signals indication and acts accordingly, typically, a signal might inform the driver of the speed at which the train may safely proceed or it may instruct the driver to stop. Originally, signals displayed simple stop/proceed indications, as traffic density increased, this proved to be too limiting and refinements were added. One such refinement was the addition of distant signals on the approach to stop signals, the distant signal gave the driver warning that he was approaching a signal which might require a stop. This allowed for an increase in speed, since train drivers no longer had to drive at a speed within sighting distance of the stop signal. Under timetable and train operation, the signals did not directly convey orders to the train crew. Instead, they directed the crew to pick up orders, possibly stopping to do so if the order warranted it, signals are used to indicate one or more of the following, that the line ahead is clear or blocked. That the driver has permission to proceed, the speed the train may travel. The state of the next signal and that the train orders are to be picked up by the crew. Signals can be placed, at the start of a section of track, on the approach to a movable item of infrastructure, such as points/switches or a swingbridge. in advance of other signals. On the approach to a level crossing, ahead of platforms or other places that trains are likely to be stopped. Running lines are usually continuously signalled, each line of a double track railway is normally signalled in one direction only, with all signals facing the same direction on either line. Where bi-directional signalling is installed, signals face in both directions on both tracks, signals are generally not provided for controlling movements within sidings or yard areas. The aspect is the appearance of the signal, the indication is the meaning. In American practice the indications have conventional names, so that for instance Medium Approach means Proceed at not exceeding medium speed and it is important to understand that for signals that use coloured aspects, the colour of each individual light is subsumed in the overall pattern. In the United States, for example, it is common to see a Clear aspect consisting of a light above a red light. The red light in this instance does not indicate Stop, it is simply a component of a larger aspect. Operating rules normally specify that there is some imperfection in the display of an aspect
5.
Single-track railway
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A single-track railway is a railway where trains travelling in both directions share the same track. Single track is found on lesser-used rail lines, often branch lines. Single track is significantly cheaper to build, but has operational, for example, a single-track line that takes 15 minutes to travel through would have capacity for only two trains per hour in each direction. By contrast, a track with signal boxes four minutes apart can allow up to 15 trains per hour in each direction. This hindrance on the capacity of a track may be partly overcome by making the track one-way on alternate days. Long freight trains are a problem if the passing stretches are not long enough, other disadvantages include the propagation of delays, since one delayed train on a single track will also delay any train waiting for it to pass. Also, a single track does not have a track that can allow a reduced capacity service to continue if one track is closed. These consist of stretches of double track, usually long enough to hold one train. The capacity of a line is determined by the number of passing loops. Passing loops may also be used to trains heading in the same direction at different speeds to overtake. Some form of signalling system is required, in traditional British practice, single-track lines were operated using a token system where the train driver had to be in possession of a token in order to enter a stretch of single track. Because there was one unique token issued at any one time for each stretch of single track. This method is used on some minor lines but in the longest single-track lines in Britain this has been superseded by radio communication. This generally worked but was inflexible and inefficient and it was improved with the invention of the telegraph and the ability to issue train orders. Converting a single-track railway to double track is called duplication or doubling, converting double track to track is known as singling. A double-track railway operating only a track is known as single-line working. Building bike trails on rail corridors has occurred in limited examples, also reclaiming a railway corridor to use trains again, that have become bike paths, limits the use of double tracks. The bike path is usually where the track would be
6.
Double-track railway
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A double-track railway usually involves running one track in each direction, compared to a single-track railway where trains in both directions share the same track. In the earliest days of railways in the United Kingdom, most lines were built as double-track because of the difficulty of co-ordinating operations before the invention of the telegraph, the lines also tended to be busy enough to be beyond the capacity of a single track. In the early days the Board of Trade did not consider any single-track railway line to be complete and this improved with the development of the telegraph and the train order system. In any given country, rail traffic generally runs to one side of a double-track line, thus in Belgium, China, France, Sweden, Switzerland and Italy for example, the railways use left-hand running, while the roads use right-hand running. In countries such as Indonesia, it is the reverse, on the French-German border, for example, flyovers were provided so that train moving on the left in France end up on the right in Germany and vice versa. Handedness of traffic can affect locomotive design, for the driver, visibility is good from both sides of the driving cab so the choice on which side to site the driver less important. For example, the French SNCF Class BB7200 is designed for using the left-hand track, generally, the left/right principle in a country is followed mostly on double track. On single track, when trains meet, the train that shall not stop uses the straight path in the turnout. Double-track railways, especially older ones, may use each track exclusively in one direction and this arrangement simplifies the signalling systems, especially where the signalling is mechanical. Where the signals and points or rail switches are power-operated, it can be worthwhile to signal each line in both directions, so that the line becomes a pair of single lines. This allows trains to use one track where the track is out of service due to track maintenance work, or a train failure. Most crossing loops are not regarded as even though they consist of multiple tracks. If the crossing loop is long enough to several trains. A more modern British term for such a layout is an extended loop, the distance between the track centres makes a difference in cost and performance of a double-track line. The track centres can be as narrow and as cheap as possible, signals for bi-directional working cannot be mounted between the tracks so must be mounted on the wrong side of the line or on expensive signal bridges. Track centres are usually wider on high speed lines, as pressure waves knock each other as high-speed trains pass, narrow track centres might be 4 metres or less. Narrow track centres may have to be widened on sharp curves to allow for rail vehicles following the arc of the curve. Widening a track centre to 5 metres or so suits high-speed trains passing each other, increasing width of track centres of 6 metres or more makes it much easier to mount signals and overhead wiring structures
7.
Train order operation
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The system used a set of rules when direct communication between train dispatchers and trains was limited or non-existent. Trains would follow a predetermined operating plan, known as the timetable, unless superseded by train orders conveyed to the train from the dispatcher, Train order operation was a system that required minimum human overhead in an era before widespread use of technology-based automation. It was the most practical way for railroads with limited resources, or lines with limited traffic. To this day, a number of short lines, heritage railways. Train order operation has been almost completely replaced by modern operating methods. While the last traditional long hand train order form was issued on September 3,2012, timetable, the second to last train order holdout, the Chicago South Shore and South Bend Railroad, had retired its system in 2011. Timetable and train operation was widely used on North American railroads that had a single Main Track with periodic passing sidings. Timetable and train orders were used to determine which train had the right of way at any point along the line, a train which had the right of way over another train was said to be the superior train. Trains could be superior by right, by class or by direction, while a train dispatcher could establish right via train orders, the operating timetable established scheduled trains, their class and the superior direction. The class designation of a train equates to its priority with passenger trains having the highest, freight trains having less, in case of trains of the same class meeting the superior direction would then apply. On single track lines, the timetable specifies the points at which two trains would meet and pass. It would be the responsibility of the train to clear the main track a safe time before the superior train is scheduled to pass. The timetable thus provides the framework for train movement on a particular portion of the railroad. Deviations from the operation would be enacted through train orders sent from the train dispatcher to block operators. These orders would override the established timetable priorities and provide trains with explicit instructions on how to run, Train orders consisted of two types, Protection and Authority. Protective train orders would be used to ensure that no trains would be at risk of colliding with another along the line. Once the protective orders had been delivered to operators, an authority could be issued to a train to move over the line where protection had been established. Timetable and train order operation supplanted earlier forms of timetable only, the ability for a single dispatcher to issue train orders was enabled by the invention of the electric telegraph in the 1840s
8.
Menheniot railway station
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Menheniot railway station serves the village of Menheniot in Cornwall, United Kingdom. The station is managed by Great Western Railway, whose local trains serve the station, the station opened with the Cornwall Railway on 4 May 1859. It was described at the time as of small extent, consisting of a departure station, at the arrival side of the line a stone erection, with a covered seat, has been provided, but no enclosed room. The following year saw two cottages built for the use of the staff working here. The stone erection is still in existence, used as a waiting shelter, the Cornwall Railway was amalgamated into the Great Western Railway on 1 July 1889. The Great Western Railway was nationalised into British Railways from 1 January 1948 which was privatised in the 1990s, under British railways the staff were removed from the station, and from 17 May 2009 the station is only served on request. The station also has a new footbridge as from 17 May 2009, on 2 December 1873 two goods trains arrived at the station where they could pass each other before resuming their journey on the single tracks towards St Germans and Liskeard. The crossing loop was not at that time equipped with starting signals, the train for the latter had a clear line and so the signalman called out All right Dick, to the guard. Unfortunately the guard for the train was also called Dick and so told his driver to start. The accident illustrated the need for starting signals, block working, an accident occurred on 9 February 1897 during the reconstruction of Coldrennick Viaduct, which is situated just outside the station. A gang of 17 workmen were suspended below the viaduct on a platform when it broke away, two of the gangers were criticised for not fixing safety chains and using poor quality wood for the platforms. Another accident happened on 15 November 1897 during the reconstruction of nearby Treviddo Viaduct, on this occasion a rope gave way while five men were hoisting a wooden beam up onto the new viaduct. One of them let go of his rope too soon, this meant that the wood swung free, Menheniot is served by a limited number of the Great Western Railway trains on the Cornish Main Line between Penzance and Plymouth, including a few that run through beyond Plymouth. It is only served on request which means that people wishing to alight need to inform the guard, and those wishing to join the train here need to signal clearly to the driver
9.
Thorpe rail accident
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The Thorpe rail accident occurred on 10 September 1874, when two trains were involved in a head-on collision at Thorpe St Andrew in the English county of Norfolk. The accident occurred on what was then a rail line between Norwich railway station and Brundall. The two trains involved were the 20,40 mail from Yarmouth and the 17,00 express from London to Yarmouth, on this occasion trains were running late. In such circumstances, when the timetable was upset, drivers had to have authority to proceed further. Due to a series of errors, both received their authority, and anxious to make up for lost time, set off at speed along the single track. The accident, when it occurred around 21,45, resulted in both locomotives rearing into the air, and carriages reduced to wreckage, both drivers and firemen were killed, as were 17 passengers with 4 later dying from their injuries. 73 passengers and two guards were seriously injured. The Canoe River train crash in Canada in 1950 also involved two trains, controlled by telegraphed orders, authorized to enter the same section in opposite directions. Illustrated London News report History feature on the disaster by BBC Radio Norfolk Broadland Memories
10.
Track circuit
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A track circuit is a simple electrical device used to detect the absence of a train on rail tracks, used to inform signallers and control relevant signals. The basic principle behind the circuit lies in the connection of the two rails by the wheels and axle of locomotives and rolling stock to short out an electrical circuit. This circuit is monitored by electrical equipment to detect the absence of the trains, since this is a safety appliance, fail-safe operation is crucial, therefore the circuit is designed to indicate the presence of a train when failures occur. On the other hand, false occupancy readings are disruptive to operations and are to be minimized. Track circuits allow railway signalling systems to operate semi-automatically, by displaying signals for trains to slow down or stop in the presence of occupied track ahead of them. They help prevent dispatchers and operators from causing accidents, both by informing them of track occupancy and by preventing signals from displaying unsafe indications, a track circuit typically has power applied to each rail and a relay coil wired across them. When no train is present, the relay is energised by the current flowing from the source through the rails. When a train is present, its axles short the rails together, the current to the relay coil drops. Circuits through the relay contacts therefore report whether or not the track is occupied, each circuit detects a defined section of track, such as a block. These sections are separated by insulated joints, usually in both rails, to prevent one circuit from falsely powering another in the event of insulation failure, the electrical polarity is usually reversed from section to section. Circuits are powered at low voltages to protect against line power failures, the relays and the power supply are attached to opposite ends of the section to prevent broken rails from electrically isolating part of the track from the circuit. A series resistor limits the current when the circuit is short-circuited. In some railway electrification schemes, one or both of the rails are used to carry the return current. This prevents use of the basic DC track circuit because the substantial traction currents overwhelm the small track circuit currents. To accommodate this, AC track circuits use alternating current signals instead of current but typically. The relays are arranged to detect the frequency and to ignore DC. Again, failsafe principles dictate that the relay interprets the presence of the signal as unoccupied track, the AC signal can be coded and locomotives equipped with inductive pickups to create a cab signalling system. There are two approaches to provide a continuous path for traction current that spans multiple track circuit blocks
11.
South Devon Railway (heritage railway)
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The South Devon Railway is a 6.64 miles heritage railway from Totnes to Buckfastleigh in Devon. Mostly running alongside the River Dart, it was known as the Dart Valley Railway. The railway is now operated by the South Devon Railway Trust, the Railways headquarters and museum are located at Buckfastleigh railway station. The line was built by the Buckfastleigh, Totnes and South Devon Railway and it was worked by the larger South Devon Railway Company until 1 February 1876 when this was amalgamated into the Great Western Railway. The Buckfastleigh line was taken over by the Great Western Railway in 1897, the railway was nationalised on 1 January 1948. The line closed to all traffic on 7 September 1962 and was re-opened as the Dart Valley Railway, the South Devon Railway Trust took over the running of the line on 1 January 1991. The South Devon Railway was named the Heritage Railway of the Year in 2007, a plaque on the station wall commemorates the event. The South Devon Railway Trust bought the freehold of the line from Dart Valley Railway plc on 8 February 2010, the line is 6 miles and 51 chains long It stretches from Totnes to Buckfastleigh. Staverton is the intermediate station on the line. Just north of Staverton is a signal box known as Bishops Bridge where there is the passing loop on the line. For most of its route, the runs along the left bank of the River Dart. This means that the river, and the best views, can be seen to the left of the train when facing Buckfastleigh, trains on the South Devon Railway operate daily from late March to the end of October. On most days a single train set operates, providing four journeys a day in each direction, on busy days two train sets operate, providing more journeys. Other services include evening Dining trains, fish n chip trains, also the railway runs both full day steam and diesel footplate experience courses throughout the year. The railway is used as a filming location for period films. It featured in scenes of the BBCs 2015 miniseries And Then There Were None. The rolling stock preserved on line include many examples of steam locomotives typical of the Great Western Railway types that would have worked on it. There are also types of steam locomotives and a number of diesel locomotives
12.
Token (railway signalling)
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In railway signalling, a token is a physical object which a locomotive driver is required to have or see before entering onto a particular section of single track. The token is clearly endorsed with the names of the section it belongs to, a token system is used for single lines because of the very much greater risk of serious collision in the event of irregular working by signalmen or traincrews, than on double lines. Such a system is known as one engine in steam, such schemes were used, and indeed still are used on some branches of rail networks, and on heritage railways. The main problem with such a scheme is that it is best suited to an isolated branch of single track line. That object is known as a token and is marked to indicate to which single track section it belongs. Tokens have existed in a variety of forms, staff tablet ball key The token system was developed in Britain in the 19th century. If a branch line is an end with a simple shuttle train service. The driver of any entering the branch line must be in possession of the token. For convenience in passing it from hand to hand, the token was often in the form of a staff, typically 800 mm long and 40 mm diameter, and is referred to as a train staff. Such a staff is usually literally a wooden staff with a brass plate stating the two signal boxes between which it is valid, in UK terminology, this method of working on simple branch lines was originally referred to as One Engine in Steam, and later One Train Working. That really does cause a delay because if the staff is not there. Using only a single token does not provide convenient operation when consecutive trains are to be worked in the same direction and he was given a written authority to enter the single line section, referred to as the ticket. He could then proceed, and a train could follow. In the earliest days the train could proceed after a designated time interval. However, following the Armagh rail disaster of 1889, block working became mandatory, seeing the train staff provided assurance that there could be no head-on collision. To ensure that the ticket is not issued incorrectly, a book of numbered tickets is kept in a locked box, the key to which is permanently fastened to the token, or is the token. In addition, the lock prevents the token being removed until the box is closed. Once a ticket is issued, its number is recorded in a Train Register book, and this system is known as staff and ticket
13.
Absolute block signalling
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Absolute block signalling is a British signalling scheme designed to ensure the safe operation of a railway by allowing only one train to occupy a defined section of track at any time. This system is used on double or multiple lines where use of line is assigned a direction of travel. The electric telegraph provided the ability for signalmen to communicate each other. It successfully managed train control over most of the British railway system until generally superseded by more sophisticated systems from 1950. The object, or aim, of the block system is in itself defined fairly simply - to prevent more than one train being in a Block section on the same line at the same time. The absolute block system does not replace the use of any form of signalling, such as fixed signals, hand signals. A train approaching a section is offered by a signalman to his counterpart at the signal box. If the section is clear, the latter accepts the train, and this process is repeated for every block section a train passes through. The block instrument consists of a cabinet, its front face displays two indicators — telegraph needles — and has a commutator handle. The upper indicator shows the state of the section, on the line leading away from the signal box. The commutator is used by the signalman to indicate the state of the section approaching his signal box, all indications are repeated on a similar instrument at the other end of the block section, in the associated signal box. The commutator has three positions and each of the two indicators has three positions, normal, line clear, and train on line, either integral to the instrument or separately mounted, there is a single-stroke bell and a bell operating device, either a tapper or a plunger. The signalling bell, also known as a bell, is used in conjunction with the block instruments if the bell is not integrated with them. It is a single design and relays the codes from adjacent signal boxes. Each bell has its own sound to alert the signalman which instrument needs to be attended to. Let us consider the process of signalling a train in the up direction past a signal box B, the signal box in rear is A and the signal box in advance is C. The block indicators at B are in the Normal position, the signalman at A offers the train to B by sending an Is Line Clear. If the signalman at B can accept the train safely he accepts the train by repeating the bell signal, the Line Clear is repeated at box A, and allows the signalman at A to clear, or pull off, his signals
14.
Cab signalling
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Cab signalling is a railway safety system that communicates track status and condition information to the cab, crew compartment or drivers compartment of a locomotive, railcar or multiple unit. The information is continually updated giving an easy to display to the train driver or engine driver. The simplest systems display the signal, while more sophisticated systems also display allowable speed, location of nearby trains. The main purpose of a system is to enforce a safe separation between trains and to stop or slow trains in advance of a restrictive situation. The first such systems were installed on a basis in the 1910s in the United Kingdom, 1920s in the United States. In North America, the track circuit system developed by the Pennsylvania Railroad. All cab signalling systems must have a continuous in-cab indication to inform the driver of track ahead, however. Intermittent cab signals are updated at discrete points along the rail line, continuous cab signals receive a continuous flow of information about the state of the track ahead and can have the cab indication change at any time to reflect any updates. The majority of cab signalling systems, including those that use coded track circuits, are continuous, the British Automatic Warning System, German Indusi, and Dutch ATB-NG fall into this category. Failure to acknowledge the tone will result in brake application, but even after acknowledgement, continuous systems have the added benefit of fail safe behaviour in the event a train stops receiving the continuous event relied upon by the cab signalling system. Early systems use the rails or loop conductors laid along the track to provide communication between wayside signal systems and the train. Cab signals require a means of transmitting information from wayside to train, there are a few main methods to accomplish this information transfer, Electric/magnetic Inductive Coded track circuits. Transponder Wireless This is popular for early intermittent systems that used the presence of a field or electric current to designate a hazardous condition. The British Rail Automatic Warning System is an example of a cab signal system transmitting information using a magnetic field. Inductive systems are systems that rely on more than the simple presence or absence of a magnetic field to transmit a message. Inductive systems typically require a beacon or a loop to be installed at every signal. The inductive coil uses a magnetic field to transmit messages to the train. Typically, the frequency of pulses in the coil are assigned different meanings
15.
Centralized traffic control
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Centralized traffic control is a form of railway signalling that originated in North America. CTC consolidates train routing decisions that were carried out by local signal operators or the train crews themselves. The system consists of a train dispatchers office that controls railroad interlockings. One hallmark of CTC is a panel with a graphical depiction of the railroad. On this panel the dispatcher can keep track of trains locations across the territory that the dispatcher controls, larger railroads may have multiple dispatchers offices and even multiple dispatchers for each operating division. These offices are located near the busiest yards or stations. Key to the concept of CTC is the notion of control as it applies to railroads. Trains moving in opposite directions on the same track cannot pass each other without special infrastructure such as sidings, the starting point of each system was the railroad timetable that would form the advanced routing plan for train movements. Trains following the timetable would know when to take sidings, switch tracks, however if train movements did not go as planned the timetable would then fail to represent reality, and attempting to follow the printed schedule could lead to routing errors or even accidents. This was especially common on single-track lines that comprised the majority of railroad route miles in North America, therefore, timetable operation was supplemented with train orders, which superseded the instructions in the timetable. The development of Direct Traffic Control via radio or telephone between dispatchers and train crews made telegraph orders largely obsolete by the 1970s. Where traffic density warranted it, multiple tracks could be provided, trains running counter to this flow of traffic would still require train orders, but other trains would not. Such a Mexican standoff not only represents a safety hazard, before the advent of CTC there were a number of solutions to this problem that did not require the construction of multiple single direction tracks. In areas of traffic density, sometimes bi-directional operation would be established between manned interlocking towers. Each section of track would have a traffic control lever associated with it to establish the direction of traffic on that track. Often, both towers would need to set their traffic levers in the way before a direction of travel could be established. Block signals in the direction of travel would display according to track conditions, furthermore, no train could be routed into a section of track against its flow of traffic and the traffic levers would not be able to be changed until the track section was clear of trains. Both APB and manual control would still require train orders in certain situations
16.
Direct traffic control
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Direct traffic control is a system for authorizing track occupancy used on some railroads instead of or in addition to signals. In DTC, controlled tracks and sidings are divided into pre-specified blocks, in addition to being listed by milepost in the railroads timetable, block limits are delineated by conspicuous signs along the tracks. Every portion of controlled track belongs to a block, as blocks are laid out back-to-back along the length of the rail line. For example, a 30-mile length of main track may be divided into three blocks, Anna, Bess, and Cloy, each 10 miles long. At milepost 10, there will be a sign displaying the end of Anna block and the beginning of Bess block, a train authorized in Anna through Bess blocks must stop before Bess block ends and Cloy block begins. For example, a length of track may consist of three blocks, there is a siding at Bess, and this siding is specified as Bess Siding. Both Bess and Bess Siding blocks extend to the switches at either end of the siding, Anna and Cloy blocks begin on the other side of their respective switches. Neither Bess nor Bess Siding blocks may be occupied without authority from the train dispatcher, in this example, a train may have authority straight through from Anna through Cloy. Lengths of DTC blocks vary but usually take about 10 minutes to traverse, the siding itself is not considered a DTC block per se, but in some situations sidings must not be occupied without authority from the train dispatcher. If a train could not use the track in Bess. This is not done when the track is available, as there is a speed disadvantage to having the train traverse the slower siding track. While most DTC blocks are laid out back-to-back, the blocks actually do not touch at sidings, instead, there is a gray area over the sidings switches, and the main tracks and sidings DTC blocks begins at approximately the clearance point of the switch. The area over the switch must not be occupied unless authority is granted in blocks on both sides of the switch, for example, a train authorized only in Anna block must stop at the End Anna Block sign, which is a short distance from the switch points. A train authorized in Anna through Bess or in Anna through Bess Siding may proceed past the End Anna Block sign, over the switch, blocks are typically named after a distinguishing feature within the block, such as a station, town, or river. Barring human error, this ensures that no two trains are ever authorized on any piece of track at the same time, thereby preventing collisions. Another key feature of DTC is that one authority is in effect for any given train at any given time. When a dispatcher issues a new authority to a train, the previous authority becomes invalid, in modern implementations, dispatchers rely on computerized systems to keep track of trains that have received authority. Typically, the computer will prevent the dispatcher from giving two trains authority over the same track, the computer system generally displays a highly simplified mock-up of the track, displaying the block limits and sidings
17.
Radio Electronic Token Block
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Radio Electronic Token Block is a system of railway signalling used in the United Kingdom. It is a development of the token system for controlling traffic on single lines. On arrival at an exchange point, the driver reports his/her position to the signaller by radio. If the signaller is in a position to do so, he/she will issue the electronic token applicable to the section ahead, simultaneously, the driver must operate a button on an apparatus in the cab to receive the token. The token is then transmitted to the train by radio, the Solid State Interlocking controlling the system prevents the issue of any token permitting conflicting movements. This token is the authority to occupy the line. The fixed distant board on the approach has a single permanent AWS inductor which gives a warning in the cab regardless of the signal box instruction and has to be cancelled when passed. In the facing direction, an indicator is provided to indicate to the driver that the points are correctly set. The points indicator is in the form of a yellow light, the whole line can be operated by just one or two signallers and needs very little infrastructure other than the track itself, making it a very cost-effective method. The simplicity of the infrastructure in RETB areas was reduced by the installation of the Train Protection & Warning System. A train stop loop is provided at each stop board, and is normally activated, when the signaller issues a token for a train to enter a section, the TPWS loop at the appropriate board is deactivated, so allowing the train to proceed. Indication of the state of the TPWS is provided by a light mounted below the stop board. This shows a blue light when the TPWS is activated. The genesis of the system was on the Far North Line, the manual issue of the tokens continued as before. The line selected for the trial was another remote and lightly used Scottish line, the contract was placed with Westinghouse of Chippenham, Wiltshire, and the system was brought into use on 28 October 1984, with the control equipment situated at Dingwall. Over the next four years, control was transferred to Inverness, a new control centre was brought into use at Banavie for the West Highland Line from Helensburgh Upper to Fort William and Mallaig, and from Crianlarich to Oban. RETB is being replaced with the new European in-cab signalling system. The Cambrian line was due to be changed over to the new system by Spring 2010 but was delayed, RETB was phased out on the East Suffolk Line after the last Ipswich-Lowestoft service arrived at Oulton Broad South on Friday 19 October 2012
18.
Railway signalling
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Railway signalling is a system used to direct railway traffic and keep trains clear of each other at all times. Trains move on fixed rails, making them susceptible to collision. This susceptibility is exacerbated by the weight and inertia of a train. Most forms of control involve movement authority being passed from those responsible for each section of a rail network to the train crew. The set of rules and the equipment used to accomplish this determine what is known as the method of working. Not all these methods require the use of signals. The earliest rail cars were first hauled by horses or mules, a mounted flagman on a horse preceded some early trains. Hand and arm signals were used to direct the “train drivers”, foggy and poor-visibility conditions gave rise to flags and lanterns. Wayside signalling dates back as far as 1832, and used elevated flags or balls that could be seen from afar, the simplest form of operation, at least in terms of equipment, is to run the system according to a timetable. Every train crew understands and adheres to a fixed schedule, trains may only run on each track section at a scheduled time, during which they have possession and no other train may use the same section. When trains run in opposite directions on a railroad, meeting points are scheduled. Neither train is permitted to move before the other has arrived, in the US the display of two green flags is an indication that another train is following the first and the waiting train must wait for the next train to pass. In addition, the carrying the flags gives eight blasts on the whistle as it approaches. The waiting train must return eight blasts before the flag carrying train may proceed, the timetable system has several disadvantages. First, there is no confirmation that the track ahead is clear. A second problem is the systems inflexibility, trains cannot be added, delayed, or rescheduled without advance notice. A third problem is a corollary of the second, the system is inefficient, to provide flexibility, the timetable must give trains a broad allocation of time to allow for delays, so the line is not in the possession of each train for longer than is otherwise necessary. Nonetheless, this system permits operation on a vast scale, with no requirements for any kind of communication that travels faster than a train, timetable operation was the normal mode of operation in North America in the early days of the railroad
19.
Automatic block signaling
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Automatic block signaling, or ABS, is a railroad communications system that consists of a series of signals that divide a railway line into a series of sections, or 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 introduction of ABS reduced railways costs and increased their capacity, older manual block systems required human operators. The automatic operation comes from the ability to detect whether blocks are occupied or otherwise obstructed. The system operates without any intervention, unlike more modern traffic control systems that require external control to establish a flow of traffic. The earliest way of managing multiple trains on one track was by use of a timetable, operation of trains by timetable alone was supplemented by telegraphed train orders beginning in 1854 on the Erie Railroad. A railroad company dispatcher would send train orders to stations manned by telegraphers, a manual block system in the United States was implemented by the Pennsylvania Railroad about 1863, a couple of decades before other American railroads began using it. This system required a railroad employee stationed at each signal to set the signals according to instructions received by telegraph from dispatchers. English railroads also used a controlled manual block system, which was adapted for use in the U. S. by the New York Central and Hudson River Railroad in 1882. Automatic block signaling was invented in America, and first put to use by the Eastern Railroad of Massachusetts in 1871, the rest of the nations trackage was operated by timetable and train order. Where blocks are short or higher capacity is needed, four or more blocks are used, the most common way that ABS systems detect track occupancy is through the use of electrical track circuits. A low-voltage current is sent through the track between the signals and is detected to determine whether the circuit is closed, open, or shorted, a trains metal wheels and axles will pass current from one rail to the other, thereby shorting the circuit. In the United Kingdom the system is referred to as track circuit block to avoid confusion with the use, in that country, ABS system electronics are also able to detect breaks in the rail or improperly lined track switches, which result in an open circuit. These will also change the signal indication, preventing any trains from entering the block, ABS would be set up in such a way to cover train movements only in a single direction for each track. The movement of running in that direction would be governed by the automatic block signals which would supersede the normal superiority of trains. Movement of trains operating against the flow of traffic would still require train orders or other special manual protections to prevent a collision. Therefore, under ABS operation trains moving in the direction is an uncommon occurrence. Another feature of single direction ABS lines is the use of non-interlocked crossovers to facilitate wrong direction running or trains reversing direction away from a traditional terminal
20.
Communications-based train control
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Communications-based train control is a railway signaling system that makes use of the telecommunications between the train and track equipment for the traffic management and infrastructure control. By means of the CBTC systems, the position of a train is known more accurately than with the traditional signaling systems. This results in an efficient and safe way to manage the railway traffic. Metros are able to improve headways while maintaining or even improving safety, as defined in the IEEE1474 standard. The main objective of CBTC is to increase capacity by reducing the interval between trains. Traditional signalling systems detect trains in sections of the track called blocks. Since every block is a section of track, these systems are referred to as fixed block systems. As a result, Bombardier opened the worlds first radio-based CBTC system at San Francisco airports Automated People Mover in February 2003, a few months later, in June 2003, Alstom introduced the railway application of its radio technology on the Singapore North East Line. Previously, CBTC has its origins in the loop based systems developed by Alcatel SEL for the Bombardier Automated Rapid Transit systems in Canada during the mid-1980s. See SelTrac for further information regarding Transmission-Based-Train-Control, as with new application of any technology, some problems arose at the beginning mainly due to compatibility and interoperability aspects. However, there have been relevant improvements since then, and currently the reliability of the communication systems has grown significantly. Moreover, it is important to highlight that not all the systems using radio communication technology are considered to be CBTC systems, CBTC systems are modern railway signaling systems that can mainly be used in urban railway lines and APMs, although it could also be deployed on commuter lines. For main lines, a system might be the European Railway Traffic Management System ERTMS Level 3. In the modern CBTC systems the trains continuously calculate and communicate their status via radio to the wayside equipment distributed along the line and this status includes, among other parameters, the exact position, speed, travel direction and braking distance. This information allows calculation of the area occupied by the train on the track. It also enables the wayside equipment to define the points on the line that must never be passed by the trains on the same track. These points are communicated to make the trains automatically and continuously adjust their speed while maintaining the safety, so, the trains continuously receive information regarding the distance to the preceding train and are then able to adjust their safety distance accordingly. From the signalling system perspective, the first figure shows the total occupancy of the train by including the whole blocks which the train is located on
21.
European Train Control System
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ETCS requires standard trackside equipment and a standard controller within the train cab. In its final form, all information is passed to the driver electronically, removing the need for lineside signals that, at high speed. It is a requirement that all new, upgraded or renewed tracks and rolling stock in the European railway system should adopt ETCS. Many networks outside the EU have also adopted ETCS, generally for high-speed rail projects, ETCS is specified at four different levels, Level 0, ETCS-compliant locomotives or rolling stock interact with lineside equipment that is non-ETCS-compliant. Versions are called System Requirement Specification and this is a bundle of documents, which may have different versioning for each document. A main version is called Baseline, unfortunately was a long time no strait release management and so exists no clear numbering scheme and hidden differences in practical installation until BL3. The European railway network grew from separate national networks with more in common than standard gauge. Notable differences include voltages, loading gauge, couplings, signalling, both factors led to efforts to reduce the time and cost of cross-border traffic. On 4 and 5 December 1989, a group including Transport Ministers resolved a master plan for a trans-European high-speed rail network. The Commission communicated the decision to the European Council, which approved the plan in its resolution of 17 December 1990 and this led to a resolution on 91/440/EEC as of 29 July 1991, which mandated the creation of a requirements list for interoperability in high-speed rail transport. The rail manufacturing industry and rail network operators had agreed on creation of interoperability standards in June 1991, until 1993 the organizational framework was created to start technical specifications that would be published as Technical Specifications for Interoperability. The mandate for TSI was resolved by 93/38/EEC, in 1995 a development plan first mentioned the creation of the European Rail Traffic Management System. The specification was written in 1996 in response to EU Council Directive 96/48/EC99 of 23 July 1996 on interoperability of the trans-European high-speed rail system, in July 1998 SRS 5a documents were published that formed the first baseline for technical specifications. UNISIG provided for corrections and enhancements of the baseline specification leading to the Class P specification in April 1999 and this baseline specification has been tested by six railways since 1999 as part of the ERTMS. The railway companies defined some extended requirements that were included to ETCS, the SUBSET-026 is defined from eight chapters where chapter seven defines the ETCS language and chapter eight describes the balise telegram structure of ETCS Level 1. Later UNISIG published the corrections as SUBSET-108, that was accepted in decision 2006/679/EEC, the earlier ETCS specification contained a lot of optional elements that limited interoperability. The Class 1 specifications were revised in the year leading to SRS2.3.0 document series that was made mandatory by the European Commission in decision 2007/153/EEC on 9 March 2007. Annex A describes the specifications on interoperability for high-speed and conventional rail transport
22.
Signalling control
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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 signal operator and the lineside signalling equipment. The technical apparatus used to control switches, signals and block systems is called interlocking, originally, all signalling was done by mechanical means. Before long, it was realised that control should be concentrated into one building, the signal box provided a dry, climate controlled space for the complex interlocking mechanics and also the signalman. The raised design of most signal boxes also provided the signalman with a view of the railway under his control. The first use of a box was by the London and Croydon Railway in 1843 to control the junction to Bricklayers Arms in London. Power operated switch points and signalling decides greatly expanded the territory that a control point could operate from several hundred yards to several miles. As the technology of electric relay logic was developed, it no longer necessary for signalmen to operate control devices with any sort of mechanical logic at all. With the jump to all logic, physical presence was no longer needed. Another advancement made possible by the replacement of mechanical control by all systems was that the signalmans user interface could be enhanced to further improve productivity. The smaller size of electric toggles and push buttons put more functionality within reach of an individual signalman, route-setting technology automated the setting of individual points and routes through busy junctions. Computerised video displays removed the physical interface altogether, replacing it with a point-and-click or touchscreen interface, finally, the use of Automatic Route Setting removed the need for any human input at all as common train movements could be fully automated according to a schedule or other scripted logic. Signal boxes also served as important communications hubs, connecting the parts of a rail line. The first signalling systems were possible by technology like the telegraph. Later, the telephone put centralised dispatchers in contact with distant signal boxes, the ultimate ability for data to be transmitted over long distances has proven the demise of most local control signal boxes. Signalmen next to the track are no longer needed to serve as the eyes, track circuits transmit train locations to distant control centres and data links allow direct manipulation of the points and signals. In any node-based control system, proper identification is critical to ensuring that messages are received by their intended recipients. As such, signalling control points are provided with names or identifiers that minimise the likelihood of confusion during communications, popular naming techniques include using nearby geographic references, line milepost numbers, sequence numbers and identification codes
23.
Block post
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A block post in railway signalling is the signal box at one end of a block section. In Germany block posts are known as Blockstellen and are defined as railway facilities on the line that, as part of a block system. They usually have a signal in each direction and on each running line. They are mainly found where the distance between two stations is greater than average. In the early years of the railway, block posts were local signal boxes manned with block post keepers, today there are only a few of these classic, railway staff-operated block posts. Block posts are described in the German railway regulations, the Eisenbahn-Bau- und Betriebsordnung or EBO, automatic Block Signal Centralised control Block signalling Signalling block systems Token
24.
Integrated Electronic Control Centre
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The Integrated Electronic Control Centre was developed in the late 1980s by the British Rail Research Division for UK-based railway signalling centres, although variations exist around the world. It is the most widely deployed VDU based signalling system in the UK, with over 50 workstations in control centres that manage many of the most complex. ARS can also severely disrupted service patterns and assist the signaller in the event of train or infrastructure failures. IECCs were developed as an alternative to the switch or button panel control. From the start, they controlled Solid State Interlockings, a version of the traditional relay interlocking. The system can control as many miles of track as required, recently, PC-based control systems, similar to the IECC have been developed and are sold by various signalling contractors, e. g. Westinghouse Rail Systems WESTCAD. Early history The concept of IECC was developed at the Railway Technical Centre in Derby during the 1980s, and in particular the initial software for ARS and SSI. A contract for the development of a standard system was let in January 1987 to CAP Group, including the supply of a complete system for Yoker. This was the first time a house became involved in railway signalling after competing against the main incumbent suppliers of GEC-General Signal. The solution used off-the-shelf microcomputer technology to host the sub-systems of IECC in high availability configurations linked via a duplicated Nine Tiles Superlink local area network, subsequent contracts were let to CAP Group for further operational IECC systems involving the supply of turnkey hardware and software. These included the first IECC to go live at Liverpool Street in Easter 1989 quickly followed by York, in 2006, the AEA rail business became DeltaRail, who have developed IECC Scalable which replicates all the functionality of the original IECC on a modern hardware platform and software architecture. The following installations are not true IECCs of the BR/SEMA/DeltaRail design and they are VDU based signalling control systems with a similar look and feel but in most cases they do not incorporate Automatic Route Setting. * These systems, which are already in existence, are planned to be upgraded when the version of ARS has received Network Rail approval. ° Nottingham, Trent & Burton Workstations now have Hitachi ICS TREsa commissioned
25.
Interlocking
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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. The signalling appliances and tracks are collectively referred to as an interlocking plant. An interlocking is designed so that it is impossible to display a signal to proceed unless the route to be used is proven safe. A minimal interlocking consists of signals, but usually includes additional appliances such as points and derails, some of the fundamental principles of interlocking include, Signals may not be operated to permit conflicting train movements to take place at the same time. Switches and other appliances in the route must be set before a signal may allow train movements to enter that route. Railway interlocking is of British origin, where numerous patents were granted, in June 1856, John Saxby received the first patent for interlocking switches and signals. In 1868, Saxby was awarded a patent for what is today in North America as “preliminary latch locking”. Preliminary latch locking became so successful that by 1873,13,000 mechanical locking levers were employed on the London, at the time, Toucey was General Superintendent and Buchanan was Superintendent of Machinery on the NYC&HRR. Toucey and Buchanan formed the Toucey and Buchanan Interlocking Switch and Signal Company in Harrisburg, the first important installations of their mechanism were on the switches and signals of the Manhattan Elevated Railroad Company and the New York Elevated Railroad Company in 1877-78. Compared to Saxbys design, Toucey and Buchanans interlocking mechanism was more cumbersome and less sophisticated, Union Switch & Signal bought their company in 1882. The challenge facing the industry was achieving the same level of safety and reliability that was inherent to purely mechanical systems. An experimental hydro-pneumatic interlocking was installed at the Bound Brook, New Jersey junction of the Philadelphia and Reading Railroad, by 1891, there were 18 hydro-pneumatic plants, on six railroads, operating a total of 482 levers. The installations worked, but there were defects in the design. By 1900,54 electro-pneumatic interlocking plants, controlling a total of 1,864 interlocking levers, were in use on 13 North American railroads. This type of system would remain one of two competing systems into the future, although it did have the disadvantage of needing extra single-use equipment. Interlockings using electric motors for moving switches and signals became viable in 1894, another interlocking of this type was installed in Berlin Westend in 1896. By 1913, this system had been installed on 83 railroads in 35 US States and Canadian Provinces. Interlockings can be categorized as mechanical, electrical, or electronic/computer-based, in mechanical interlocking plants, a locking bed is constructed, consisting of steel bars forming a grid
26.
Lever frame
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Mechanical railway signalling installations rely on lever frames for their operation to interlock the signals and points to allow the safe operation of trains in the area the signals control. Located in the box, the levers are operated by the signalman. The worlds biggest signal box is Severn Bridge Junction at Shrewsbury it has 180 levers making it the biggest, in not only the UK, but the World. By the movement of individual levers, signals, points, level crossing gates or barriers and sometimes movable bridges over waterways are operated via wires and rods. The signaller chooses the correct combination of points, facing point locks and signals to operate, the lever frame contains interlocking designed to ensure that the levers cannot be operated to create a conflicting train movement. Each interlocking installation is individual and unique to the location controlled, the interlocking may be achieved mechanically or by electric lever locks, or a combination of both. Signals or points located some distance away from the box are sometimes electrically rather than mechanically operated. Movement of the lever operates an electrical circuit controller. In the UK, it is practice to cut short the handles of any levers controlling electrical apparatus, the worlds largest lever frame is thought to be in the Spencer Street No.1 signal box in Melbourne, Australia. Signallers are often seen using towels to cover the handles of the levers and this is to prevent sweat from the operators hands transferring to the handle and corroding the metal. A ground frame is a lever frame located beside a railway. A ground frame does not normally require any form of shelter since it is operated by traincrew. In some situations, signals may be worked from a ground frame, in most cases, a ground frame has to be released from a signal box before it can be used. Typical methods of release include, Mechanical midway release, once the ground frame has been released, the other levers controlling the points could be moved. When shunting was completed, the release cannot be restored until all levers are set back to their normal positions, the train would then continue on its way. To achieve this, a token instrument would be provided in a hut near the ground frame. Once the train was off the line, the points would be set back to normal. The modern equivalent of a frame, with switches instead of levers, is called a Ground Switch Panel
27.
Solid State Interlocking
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SSI utilises a 2-out-of-3 redundancy architecture, whereby all safety-critical functions are performed in three separate processing lanes and the results voted upon. An SSI interlocking cubicle comprises three Interlocking Processors or Multi Processor Modules, two Panel Processors and a Diagnostics Processor, an SSI system can operate on two MPMs in the event of the failure of one. It does not need the DMPM to function as an interlocking, geographic interlocking data, relating to the area of railway under control, is installed using EPROMs contained in plug in memory modules. The interlocking program contained in each of the MPMs interprets this data to allow passage of trains through its area of control. Trackside equipment such as signals and points are connected to nearby trackside functional modules, each module has a number of outputs and inputs. Each output drives an individual function, such as a lamp or an AWS inductor. Certain outputs are capable of driving a flashing lamp directly, the inputs are used to send information back to the interlocking, such as indications determined by track circuit relays or points detection circuits, for example. There are two kinds of TFM, the module and the points module. A maximum of 63 TFMs may be addressed by one SSI interlocking, in practice the number will be limited by timing issues, communication between interlockings and TFMs is by electronic data packages termed telegrams. Telegrams are transmitted via data links, comprising twisted pair copper cable, the data links are duplicated for availability. A data link module is the interface between the link and the TFMs. For transmission over distances, fibre-optic cable and pulse-code modulation may be used. Another type of module, the long distance terminal is available for this purpose, an LDT has a gold coloured label. SSI is widely installed within Great Britain, and has some penetration of other Western European markets and it was first used at Dingwall in 1984 in connection with RETB signalling. The first conventional SSI scheme was at Leamington Spa in 1985, the second and third were installed at Midway and Lenz stations in South Africa. SSI has also installed in Indonesia, Hong Kong and other countries. Due to the success of SSI within the UK market, Alstom, in particular, both re-use the SSI data preparation language and trackside equipment. A big advantage of later versions of CBI is that the arbitrary limit of 63 TFM is raised so high that a big interlocking can be handled without having to split the logic into small chunks
28.
Application of railway signals
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Tram lines frequently employ running on sight without any signals. Where movement authorities are passed to drivers exclusively by means other than fixed signals, e. g. by written or verbal authority, token, Signals exist primarily to pass instructions and information to drivers of passing trains. The driver interprets the signals indication and acts accordingly, the most important indication is danger, which means stop. Not every signal is equipped with a danger aspect, running lines are divided into sections. Under normal circumstances, only one train may occupy any section at a time, a signal is provided at the start of every section, which may only display a proceed aspect when the section ahead is completely empty, at least as far as the next signal. The length of the sections, and hence the distance between signals, determines the railways capacity, a railway with short sections can accommodate more traffic than one with long sections. The provision of signals is dependent on the use of the layout. It is not necessary to provide a signal for every conceivable movement that the layout physically permits, if, during perturbed working, a movement has to be made in a direction for which no signal is provided, this can be done under special instruction. The same applies during signal failure, a main signal controls a train movement along a running line main line. A proceed aspect on a signal indicates that the line is clear at least as far as the next signal. Trains running long distances, especially passenger trains, will travel throughout under the authority of a succession of main signals. A shunting signal controls low speed movements where provision of a signal is not appropriate. Clearance of a signal does not necessarily imply that the line ahead is clear of vehicles. Shunting signals are mounted at ground level and are smaller than main signals. A stop signal is one that is equipped to show a danger aspect and its function is to prevent conflict with other trains and to indicate that moveable infrastructure features are in the correct position. Some stop signals are in the form of a fixed signal, there is usually a panel underneath with instructions to the driver as to what circumstances he may pass the signal. Examples of such signals were used on lines signaled by the electronic token block system. A distant signal is one that cannot display a danger aspect and it is however able to display a caution aspect, which gives the driver advance warning that the stop signal ahead may be displaying danger
29.
North American railroad signals
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North American railroad signals generally fall into the category of multi-headed electrically lit units displaying speed-based or weak route signaling. There is no standard or system for railroad signaling in North America. Individual railroad corporations are free to devise their own signaling systems as long as they uphold some basic regulated safety requirements. Due to the wave of mergers that have occurred since the 1960s it is not uncommon to see a railroad operating many different types of signaling inherited from predecessor railroads. This variety can range from differences of hardware to completely different rules. While there has been some recent standardization within railroads in terms of hardware and rules and this article will explain some of the aspects typically found in North American railroad signaling. For a more technical look at how signals actually work, see North American railway signaling, there are two main types of signaling aspect systems found in North America, Speed Signaling and Weak Route Signaling. Typically railroads in the Eastern United States ran speed signaling, while railroads in the west used route signaling, with mixing of systems in the Midwest. This was due to the lower density in the west combined with generally simpler track layouts. Over time, the route signaling railroads have incorporated segments of speed signaling through merger and have adopted more speed-based aspects into their systems. Commuter railroads and Amtrak all use speed signaling where they own or maintain the tracks run on. Canadian railroads all use a system of speed signaling in Canada. North American signals are commonly of three types, Absolute - Absolute signals are usually connected to an interlocking controlled by a block operator or train dispatcher. Their most restrictive aspect is Stop and trains pass them at Stop unless they obtain special authority. Absolute signals will default to displaying Stop unless expressly cleared by a control authority, in older practice, multiple signal heads are directly above and below each other on the mast. Automatic - Automatic signals are governed by logic connected through electrical track circuits which detect the presence of trains or obstructions automatically, Automatic signals are permissive with their most restrictive aspect being one of the Restricted Proceed variety. Trains can pass a signal displaying Restricted Proceed without any outside permission. Automatic signals are recognized by having an attached number plate and in older practice
30.
Railway semaphore signal
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One of the earliest forms of fixed railway signal is the semaphore. These signals display their different indications to train drivers by changing the angle of inclination of a pivoted arm, Semaphore signals were patented in the early 1840s by Joseph James Stevens, and soon became the most widely used form of mechanical signal. Designs have altered over the years, and colour light signals have replaced semaphore signals in some countries. Note that this article doesnt represent a worldwide view of the semaphore, john Urpeth Rastrick claimed to have suggested the idea to Hutton Gregory. The semaphore was afterwards rapidly adopted as a fixed signal throughout Britain, such signals were widely adopted in the U. S. after 1908. Usually these were combined into a frame, though in some types. The arm projects horizontally in its most restrictive aspect, other angles indicate less restrictive aspects, the appropriately coloured lens, depending on the arms position, is illuminated from behind by either an oil lamp, a gas lamp, or an incandescent lamp run at a low voltage. Where a green light was required, a blue lens would usually be used, later signals using electric lamps used green lenses. Some signals converted to electric lamps from oil used a yellow-tinted bulb with the original blue lens to maintain the correct colour, materials that were commonly used to make signal posts for semaphore signals included timber, lattice steel, tubular steel and concrete. The Southern Railway in Great Britain frequently made use of old rail for signal posts, semaphores come in lower quadrant and upper quadrant forms. In a lower quadrant signal, the arm pivots downwards for the less restrictive indication, upper quadrant signals, as the name implies, pivot the arm upward for off. During the 1870s, all the British railway companies standardised on the use of semaphore signals, from the 1920s onwards, upper quadrant semaphores almost totally supplanted lower quadrant signals in Great Britain, except on former GWR lines. The advantage of the upper quadrant signal is that should the signal break, or the signal arm be weighed down by snow. In a lower quadrant signal, the opposite may happen, sending the signal to off when in fact it should be illustrating danger. Their spectacle cases, which are on the side of the spindle on which the signal arm is pivoted, are therefore required to be sufficiently heavy to prevent this happening. Current British practice mandates that semaphore signals, both upper and lower quadrant types, are inclined at an angle of 45 degrees from horizontal to display an off indication, the first railway semaphore signals had arms that could be worked to three positions, in the lower quadrant. Used in conjunction with the system, the arm horizontal meant danger, inclined downwards at 45 degrees meant caution. The vertical indication gradually came to be discontinued as the block system superseded time-interval working
31.
Axle counter
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An axle counter is a device on a railway that detects the passing of a train between two points on a track. A counting head is installed at each end of the section, and as each train axle passes the head at the start of the section. A detection point comprises two independent sensors, therefore the device can detect the direction and speed of a train by the order and time in which the sensors are passed. As the train passes a similar counting head at the end of the section, if the two counts are the same, the section is presumed to be clear for a second train. This is carried out by safety critical computers called evaluators which are centrally located, the detection points are either connected to the evaluator via dedicated copper cable or via a telecommunications transmission system. This allows the points to be located significant distances from the evaluator. This is useful when using centralised interlocking equipment but less so when signalling equipment is distributed at the lineside in equipment cabinets, the most common use for axle counters is within railway signalling for track vacancy detection. Axle counters are used for the switching on and switching off of railway crossings. Closing the crossing to pedestrian and motor vehicles when the presence of a train is detected, axle counters are used in rail yards to detect train cars as they are sorted. Axle counters are placed on the track before each switch and on track that exits the switch. Rail yard management software uses occupancy data from the counters to lock in switches. Unlike track circuits, axle counters do not require insulated rail joints to be installed and this avoids breaking the continuity of long welded rails for insulated joints to be inserted. Axle counters are particularly useful on electrified railways as they eliminate traction bonding, axle counters require no bonding and less cabling in comparison to track circuits, and are therefore generally less expensive to install and maintain. Axle counters are also useful in instances were there are issues with water on the track, generally wheel sensors work under water, as long as the wiring is above the water. Axle counters do not suffer problems with railhead contamination, e. g. that can affect the operation of track circuits. This is because the operation of axle counters does not rely on the contact of wheel with the head to provide an electrical circuit. Axle counters are used in such as wet tunnels, where ordinary track circuits are unreliable. Axle counters are also useful on steel structures, which may prevent the operation of track circuits if insulating the rails from the structure proves impracticable
32.
Track circuit interrupter
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A track circuit interrupter may be fitted at catch points, trap points or buffer stops to maintain a track circuit in the occupied state in the event of a derailment. The track circuit remains de-energised until the interrupter is replaced, trap points or catch points are designed to intentionally derail vehicles making an unauthorised movement. When a vehicle derails completely, its wheels cease to shunt the track circuit, since the vehicle might still be foul of the track, it is important to maintain the track circuit in the occupied state. To achieve this, a cast iron interrupter is fitted to one of the rails such that it will be struck by the wheels of a vehicle that is about to be derailed. Since the track circuit is bonded via the interrupter, it is proved to be intact when the track circuit relay is energised, a track circuit interrupter may be fitted behind a friction buffer stop. In the event of the stop being struck by a train and pushed along. Breaking the interrupter causes the adjacent track circuit to show occupied until the interrupter is replaced, originally, track circuit interrupters were directly connected to the rail, both physically and electrically. One of the track circuit tail cables would be connected to the interrupter, if the interrupter was broken, it was possible that the broken part, with cable still attached, could drop onto the rail and allow the track circuit to remain energised and show clear. To overcome this, it is now practice for track circuit interrupters to be insulated from the rail to which they are attached, a track circuit cable is taken via the interrupter, with one end connected to the upper part of it and another end to the lower part. The cable is at opposite polarity to the rail, therefore should the broken part of the drop onto the rail. GK/RT0011 specifies the requirements for the provision of track circuit interrupters, where vehicles derailed at trap points could foul lines other than the. In the UK, the interrupter is shown on signal box diagrams as two closed triangles inside the points, rail Accident Report 33 - a track circuit interrupter is fitted to the trap points beyond signal 53 so. Track circuit interrupter and cause signals 51 and 22 if they have been, track circuit interrupters are similar to treadles, the main difference being that interrupters remain open circuit once opened, whereas treadles reclose after activation
33.
Treadle (railway)
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In railway signalling, a treadle is a mechanical or electrical device that detects that a train axle has passed a particular location. The important difference between a treadle and a circuit is that while a track circuit detects a train over a distance as long as several kilometres. In situations where track circuits are unreliable due to rusty rails, for example adjacent to buffer stops and catchpoints, when this is depressed, the signalman gains indication of a train in a section. An electro-mechanical treadle retains a small arm that lies across the flangeway of a rail, when it is depressed, an electrical circuit controller within the unit changes its output. It remains depressed for a period of seconds, so that a train with many axles does not unduly damage the unit. An electronic treadle uses the disruption of a field to detect an axle. Hence, it can count individual axles, Electronic count heads are used in axle counter circuits that can replace track circuits completely. Variations on a treadle that can be carriage long include facing point lock bars, clearance bars, a mechanical treadle that puts a signal to stop can be replaced by a short track circuit and a reverser. A reverser is an electrically engaged latch that allows the signal to be reversed, when the track circuit past the signal is occupied, power to the latch is removed, and the signal reverts to stop, red. Reversers have been used in New South Wales especially to put starting signals to stop, when the signal was put back to stop, the system automatically sent the train on line bell signal to the station in advance. This equipment would have helped prevent the Hawes Junction rail crash, greasers use a small treadle to apply a small quantity of grease to the inside edge of the rail to reduce friction and noise between the flange of the wheel and the rail. One early signal was the Automatic signal invented by CF Whitworth, far from being automatic in operation, this was merely a signal that was operated by the signalman but returned to danger once the train had passed, by means of a treadle. After wrongly assuming the train had left the tunnel, the signalman allowed a further train to enter the tunnel. The biggest flaw in the Whitworth automatic signal is probably that it had no redundancy, on the other hand, without a treadle, the signalman is more likely to get distracted and forget to put the signal to stop. Track circuit interrupter Terminology in other Languages Induction loop used mainly for road, altpro Treadle Ansaldo Treadle Ansaldo electronic Treadle Henry Williams Treadle Schweizer Electronic Treadle UnipartRail Treadle Kelly Reverser
34.
Train protection system
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A train protection system is a railway technical installation to ensure safe operation in the event of human failure. The earliest systems were train stops, as used by the New York City Subway, the Toronto subway, the London Underground, the Moscow Subway. Beside every signal is a moveable arm, the Great Western Railway in the UK introduced its automatic train control system in the early years of the 20th century. Each distant signal had before it a ramp between the running rails, if the signal showed green, the ramp was energised with a low voltage current which was passed to the locomotive when a shoe came into contact with the ramp. A bell rang in the cab to confirm the clear aspect. If the signal showed yellow the ramp was dead and a siren sounded in the cab, if the siren was not cancelled, the brakes would automatically be applied. After the nationalisation of the railways in the UK in 1948, in this system data is transmitted magnetically between the track and locomotive by magnets mounted beside the rails and on the locomotive. Additionally, they require the driver to confirm distant signals that show stop or caution – failure to do so results in the train stopping. More advanced systems calculate a braking curve that determines if the train can stop before the red signal. They require that the train driver enter the weight and the type of brakes into the onboard computer, to overcome that problem, some systems allow additional magnets to be placed between distant and home signals, or data transfer from the signalling system to the onboard computer is continuous. Prior to the development of a train protection system in Europe. Locomotives that crossed national borders had to be equipped with multiple systems, in cases where this wasnt possible or practical, the locomotives themselves had to be changed. To overcome these problems, the European Train Control System standard was developed and it offers different levels of functionality, ranging from simple to complex. This model allows adopters to meet the cost and performance requirements of disparate solutions, the European system has been in operation since 2002 and uses GSM digital radio with continuous connectivity. The newer systems use cab signalling, where the trains constantly receive information regarding their positions to other trains. The computer shows the driver how fast he may drive, instead of him relying on exterior signals and these systems are usually far more than automatic train protection systems, not only do they prevent accidents, but also actively support the train driver. This goes as far as some systems being nearly able to drive the train automatically
35.
Advanced Civil Speed Enforcement System
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Advanced Civil Speed Enforcement System is a positive train control cab signaling system developed by Alstom. The system is designed to prevent train-to-train collisions, protect against overspeed, the information about permanent and temporary speed restrictions is transmitted to the train by transponders lying in the track, coded track circuits and digital radio. ACSES provides railway trains with positive enforcement of speed restrictions. The on-board components keep track of a position and continuously calculates a maximum safe braking curve for upcoming speed restrictions. If the train exceeds the safe braking curve then the brakes are automatically applied, temporary speed restrictions apply to all other conditions not covered by the permanent timetable, including track defects, lineside hazards and maintenance workers in and around the track area. The on-board equipment tracks the position by counting wheel rotations between a series of fixed Balises set between the rails. In the event a trains crew exceeds a speed restriction a penalty brake application is applied bringing the train to a stop in the same fashion as existing automatic train control systems. Speed restrictions required by the system are provided by the legacy Pulse code cab signaling system. The cab signal codes are fed into the ACSES cab display unit, the on-board ACSES unit is backward compatible and can function where only the cab signaling is present without the ACSES overlay as well of situations where ACSES is available without cab signals. ACSES also enforces a positive stop at signals displaying an absolute Stop indication, the system will stop the train in a Positive Stop Zone, extending up to 1000 feet from the absolute stop signal. To pass the signal or otherwise move the train in absence of a more favorable signal indication a Stop Release button must be engaged by the engineer before the brakes can be released. Due to several limitations of the ACSES system and various operations, employees must still be familiar with all permanent. The deployment of ACSES by Amtrak in 2000 created the first wide scale PTC system on the North American rail network, in the cab, the driver has a consolidated display which displays the trains ACSES target speed along with the cab signal speed and other useful operating information. Messages conveyed to and from locomotive and ground-based systems are made up of Advanced Train Control System encoded message frames, the system begins with passive transponders attached between the tracks which are electrically powered by an electromagnetic field when a locomotive passes over them. This location information is utilized by the systems when consulting its database of speed restrictions. Wayside Communications Managers link all the BCMs in the region to a network which allows them to communicate with the dispatchers office. This design provides locomotives with information about speed restrictions as soon as they go into effect without having to rely on voice communications with the train crew. Additional BCMs located at interlockings transmit information relating to absolute Stop signal indications, Speed information acquired in this fashion will be displayed on the ACSES speed readout to supplement any speed information provided by the cab signaling system
36.
ALSN
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ALSN is a train control system meaning Continuous Automatic Train Signalling used widely on the main lines of the ex-Soviet states. It uses modulated pulses inducted into rails similar to the Italian RS4 Codici, on high-speed lines the variant ALS-EN is used which takes advantage of a double phase difference modulation of the carrier wave. The name ALSN is composed of ALS, literally Automatic Locomotive Signalling, other variants are built according to the same scheme like ALST for Fixed Point Automatic Train Signalling and ALSR for Radio-Based Automatic Train Signalling. The term ALS-ARS refers to Automatic Train Signalling with Automatic Speed Regulation used in subways which is a form of a train control system. The system makes use of several distinct pulse train patterns of alternating current flowing through a circuit to convey an aspect of the next signal. The circuit comprises the feedpoint at the signal, one running rail, first locomotive axle, another running rail. The resulting electromagnetic field is picked up by receiver coils located just front of the first axle of the locomotive, the signal is then amplified, filtered and evaluated. The benefits of the system are relative simplicity and the ability to use the same signal for track occupancy detection. Since the 1990s, the Russian Railroad Company has introduced a successor system KLUB-U which requires either ALSN only or both, ALSN and ALS-EN sensors for compatibility. In ERTMS the ALSN/ALS-EN systems are listed as ETCS Class-B systems, a similar in general theory of operation, but differently implemended, is an ALS-ARS system used in subways of the former Soviet Union. In case of an overspeed, the train is unconditionally braked to the speed limit. Should be there no frequency received, the driver may proceed at a low speed while holding a vigilance pedal
37.
Automatic train control
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Automatic train control is a general class of train protection systems for railways that involves a speed control mechanism in response to external inputs. ATC can also be used with automatic operation and is usually considered to be the safety-critical part of the system. Over time there have many different safety systems labeled as automatic train control. The first was used from 1906 by the Great Western Railway, the term is especially common in Japan, where ATC is used on all Shinkansen lines and on some conventional rail lines as a replacement for ATS. The accident report for the 2006 Qalyoub accident mentions an ATC system, aTC-1 is used on the Tōkaidō and Sanyō Shinkansen since 1964. The system used on the Tōkaido Shinkansen is classified as ATC-1A, variants include ATC-1D and ATC-1W, the latter being used exclusively on the Sanyō Shinkansen. Since 2006, the Tōkaidō Shinkansens ATC-1A system has been superseded by ATC-NS, used on the Tōhoku, Jōetsu and Nagano Shinkansen routes, it utilized 0,30,70,110,160,210 and 240 km/h trackside speed limits. In recent years, ATC-2 has been superseded by DS-ATC, the Japanese ATC-2 system is not to be confused with the Ansaldo L10000 ATC system, which is similar to the EBICAB ATC system and both systems are used in parts of Continental Europe. Actually the first implementation of ATC in Japan, it was first used on Tokyo Metro Hibiya Line in 1961, both lines converted to New CS-ATC in 2003 and 2007 respectively. WS-ATC is also used on 5 Osaka Municipal Subway lines, first used on the Tokyo Metro Chiyoda Line in 1971, CS-ATC, is an analogue ATC technology using ground-based control, and, like all ATC systems, used cab signalling. CS-ATC uses trackside speed limits of 0,25,40,55,75 and 90 km/h and its use has extended to include the Tokyo Metro Ginza Line, Tokyo Metro Marunouchi Line, and most recently, the Tokyo Metro Yurakucho Line. It is also used on all Nagoya Municipal Subway lines and 3 Osaka Municipal Subway lines, introduced on the Sōbu Line and the Yokosuka Line from 1972 to 1976, it utilized trackside speed limits of 0,25,45,65,75 and 90 km/h. ATC-5 was deactivated on both lines in 2004 in favour of ATS-P, introduced in 1972, used on the Saikyō Line and Keihin-Tōhoku Line and Yamanote Line. Some freight trains were fitted with ATC-6 as well, in 2003 and 2006, the Keihin-Tōhoku and Yamanote Lines replaced their ATC-6 systems with D-ATC. Used on the Chikuhi Line in Kyushu, developed from ATC-4, ATC-10 can be partially compatible with D-ATC and completely compatible with the older CS-ATC technology. ATC-10 can be seen as a hybrid of analogue and digital technology and it is used on the Tokyo Metro Hanzomon Line, Tokyo Metro Hibiya Line, Tōkyū Den-en-toshi Line, Tōkyū Tōyoko Line and Tsukuba Express. Used on the Kaikyō Line along with Automatic Train Stop since 1988, Digital ATC is a digitized form of automatic train control in use on a few Japan Railway lines. The following forms of Digital ATC are in existence, used on non-high speed lines on some East Japan Railway Company lines
38.
Automatic train stop
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An automatic train stop or ATS is a system on a train that automatically stops a train if certain situations occur to prevent accidents. In some scenarios it functions as a type of dead mans switch, Automatic train stop differs from the concept of Automatic Train Control in that ATS does not feature an onboard speed control mechanism. The invention of the railway air brake provided an external means for stopping a train via a physical object opening a valve on the brake line to the atmosphere. Eventually known as stops or trip stops, the first mechanical ATS system was installed in France in 1878 with some railroads in Russia following suit using a similar system in 1880. In 1901 Union Switch and Signal Company developed the first North American automatic train stop system for the Boston Elevated Railway and this system was soon adopted by the New York City Subway and other rapid transit systems in the United States. Moreover, the involved in a physical tripping action can begin to damage both the wayside and vehicle borne equipment at speeds over 70 miles per hour. Electronic systems make use of electric currents or electromagnetic fields to trigger some action in the locomotive cab, without physical contact electronic systems could be used with higher speeds, limited only be the equipments ability to sense the signal from stop devices. The first such system was Le Crocodile installed on French railways starting in 1872 which used an electrified contact rail to trigger an acknowledgment from the driver. If no such acknowledgment was made in 5 seconds the train would be stopped and this system was also of the acknowledgment type and was adopted by several railroads, continuing to see service as of 2013. In 1954, Japan introduced ATS-B, the first known variant of ATS, in 1967, ATS-S was invented, the first non-contact-based ATS to be used, in 1974, ATS-P was used for the first time, and in 1986, H-ATS was invented. Since 1951 ATS has been required by the Interstate Commerce Commission as a safety requirement to allow passenger trains to exceed a speed limit of 79 mph. The popularity of ATS as a protection mechanism fell after the introduction of track coded cab signals in the 1930s. Many trains in Japan are equipped with this system, the ATS systems in Japan are slightly similar to those used in the United States, but are mostly transponder-based. The first ATS systems in Japan were introduced in the early 20th century, like the ATS systems used by the railways in the JR Group, they are transponder-based as well, but are generally incompatible with the ATS systems used by JR. In Wellington only a few signals at a junction are fitted with mechanical ATS. Some Korail and subway lines are equipped with this system, Underground lines and have ATS equipped, while, and have the more advanced Communications-based train control. Some Manchester Metrolink services are ATS equipped, however this is being phased out due to the introduction of line of sight signalling, london Underground lines are universally fitted with ATS equipment. This comprises a trip arm outside the running rail
39.
Automatic Warning System
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The Automatic Warning System is a form of limited cab signalling introduced in 1956 in the United Kingdom. The Rail Safety and Standards Board defines it as, The original concept of AWS was to provide the driver with an audible, should the driver fail to respond to a warning indication, an emergency brake application will be initiated. Since the introduction of signalling, the majority of signals are fitted with AWS. It should be noted that AWS does not relieve the driver of the responsibility of observing and obeying lineside signals and 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, AWS is part of the signalling system and warns the driver whether the next signal is clear or not. These warnings are usually given 200 yards before the signal, though the distance can vary according to linespeed, information about the signal aspect is conveyed by electromagnetic induction to the moving train through equipment fixed in the middle of the track, known as an AWS magnet. The system works by the train detecting sequences and polarities of magnetic fields passing between the equipment and the train equipment via a receiver under the train. If the signal being approached is displaying a clear for a semaphore or green for a multiple aspect colour light signal and 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, the AWS will sound a horn, the driver then has approximately 2 seconds to press the AWS/TPWS acknowledgement button. The horn then stops and the indicator changes to a pattern of black and yellow spokes. As a fail-safe mechanism, the button must be released after it has been pressed, if a driver should collapse onto the button or keep it held down, the AWS will not be cancelled. If the driver fails to cancel the warning in time the brake will apply. When this occurs the red Brake demand light will flash on the AWS/TPWS Driver machine interface, the driver must now push the AWS/TPWS acknowledgement button, and the brakes will release after a safety time out period has elapsed. AWS is provided at most main aspect signals on running lines, though there are exceptions, At through stations where the permitted speed is 30 mph or less. Where this occurs, these are called AWS gap areas, AWS magnets are not provided at semaphore stop signals. Where a line is not fitted with AWS magnets, it is shown in the Sectional Appendix, 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 locomotives whistle, in 1873, United Kingdom Patent No.3286 was granted to C. Williams for a system in which, if a signal was passed at danger, 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
40.
Balise
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A balise /bəˈliːz/ is an electronic beacon or transponder placed between the rails of a railway as part of an automatic train protection system. The French word balise is used to distinguish these beacons from other kinds of beacons, balises are used in the KVB signalling system installed on main lines of the French railway network, other than the high-speed Lignes à Grande Vitesse. Balises constitute a part of the European Train Control System. The ETCS signalling system is gradually being introduced on railways throughout the European Union, balises are also used in the Chinese Train Control System versions CTCS-2 and CTCS-3 installed on high-speed rail lines in China, which is based on the European Train Control System. A balise which complies with the European Train Control System specification is called a Eurobalise, a balise typically needs no power source. The transmission rate of Eurobalises is sufficient for a telegram to be received by a train passing at any speed up to 500 km/h. A fixed balise is programmed to transmit the data to every train. Information transmitted by a fixed balise typically includes, the location of the balise, the geometry of the line, such as curves and gradients, the programming is performed using a wireless programming device. Thus a fixed balise can notify a train of its location, and the distance to the next signal. A controllable balise is connected to a Lineside Electronics Unit, which transmits data to the train. Balises forming part of an ETCS Level 1 signalling system employ this capability, the LEU integrates with the conventional signal system either by connecting to the lineside railway signal or to the signalling control tower. Extra balises can be installed if the volume of data is too great, the balise is typically mounted on or between sleepers or ties in the centre line of the track. A train travelling at speed of 500 km/h will transmit. The earlier KER balises were specified to work up to 350 km/h, the trains on-board computer uses the data from the balises to determine the safe speed profile for the line ahead. Enough information is needed to allow the train to come to a standstill if required. The data in the balise can include the distance to the next balise and this is used to check for missing balises which could otherwise lead to a potential wrong-side failure. At the start and end of ATP equipped territory, a pair of fixed balises are often used to inform the onboard ATP equipment to start or stop supervision of the train movements. There were multiple incidents were trains had overrun a stop signal, multiple systems were invented to show the speed in the drivers cab and to provide an electronic system on the train that would prevent speeding
41.
Catch points
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Catch points and trap points are types of turnout which act as railway safety devices. Both work by guiding railway carriages and trucks from a route onto a separate. Catch points are used to derail vehicles which are out of control on steep slopes, trap points are used to protect main railway lines from unauthorised vehicles moving onto them from sidings or branch lines. Either of these arrangements may lead the vehicles into a sand drag or safety siding. A derail is another used for the same purposes as catch. Trap points are found at the exit from a siding or where a secondary track joins a main line, a facing turnout is used to prevent any unauthorised movement that may otherwise obstruct the main line. The trap points also prevent any damage that may be done by a vehicle passing over points not set for traffic joining the main line, in the United Kingdom, the use of trap points at siding exits is required by government legislation. An unauthorised movement may be due to a wagon, or may be a train passing a signal at danger. When a signal controlling passage onto a line is set to danger. Interlocking is used to make sure that the signal cannot be set to allow passage onto the line until the trap points have been aligned to ensure this movement can take place. Trap points should preferably be positioned to ensure that any unauthorised vehicle is stopped a safe distance from the main line, however, due to space limitations, it is not always possible to guarantee this. If the lines are track circuited and a wagon or train using the catchpoint could foul an adjacent line, when a train runs off it will break the track circuit and set main line signals to danger. There are several different ways of constructing trap points, A single tongue trap consists of one switch rail. This is usually placed in the rail furthest from the main line, double trap points are a full turnout, leading to two tongues. Usually the tongue nearer the main line is longer than the other, a trap road with stops is a short dead-end siding leading to some method of stopping a vehicle, such as a sand drag or buffer stop. Wide to gauge trap points have switches that work in directions and are therefore either both open or both closed. Vehicles derailed at these points will tend to continue in a direction rather than being thrown to one side. Wide to gauge points are found on sidings situated between running lines
