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48-417: In a simple case where two routes with one or two tracks each meet at a junction, a fairly simple layout of tracks suffices to allow trains to transfer from one route to the other. More complicated junctions are needed to permit trains to travel in either direction after joining the new route – for example by providing a triangular track layout. Rail transport operations refer to stations that lie on or near

96-464: A replacement bus service . It is therefore more economically viable to plan such track occupations for periods of reduced usage (e.g. 'off-peak', overnight or holiday times) to minimise the impact on normal services and revenue. Each transport system represents a contribution to a country's infrastructure , and as such must make economic sense or eventually close. From this, each has a particular role or roles. These may change with time but they affect

144-471: A traction maintenance depot , locomotives are cleaned, inspected for wear, repaired, updated, or otherwise improved. Decommissioned locomotives with steam generation capacities were sometimes positioned in semi-permanent locations and their boiler capacity was used to provide steam to heat facilities, power machinery, warm passenger cars, or snow and ice clearing activities such as defrosting railroad switches in cold weather conditions. Railroad equipment that

192-455: A busy commuter railway might have blocks a few hundred metres long. A disadvantage of fixed blocks, is that: the faster trains are permitted to run, the longer the stopping distance, and therefore the longer the blocks need to be. This decreases a line's capacity. With moving block , computers are used to calculate a 'safe zone', behind each moving train, which no other train may enter. The system depends on precise knowledge of where each train

240-417: A circular train depot, known as a roundhouse that surrounded a turntable . The presence of a work train on a given section of track will temporarily decrease the capacity of the route. The normal method in such operations is to cease other traffic altogether during the track 'occupation'. Services may be diverted by an alternative route, if available; alternatively, passenger services may be maintained using

288-463: A combination of time and speed, the computer can add the time since the train passed the transponder, and the speeds it has travelled at during that time, to then calculate exactly where the train is, even if it is between transponders. This allows the signalling system to then give a following train a movement authority, right up to the rear end of the first train. As more information comes in, this movement authority can be continuously updated achieving

336-412: A freight yard, trains are composed in a classification yard . Switcher or shunter locomotives help the composing. A unit train (also called a block train), which carries a block of cars all of the same origin and destination, does not get sorted in a classification yard, but may stop in a freight yard for inspection, engine servicing and/or crew changes. Combining freight and passenger operations on

384-582: A large part in decisions about railways, such as the Beeching Axe . In the UK , building or rebuilding a railway usually requires an Act of Parliament . In many countries, rail subsidies allow unprofitable, but socially desirable, railways to continue to operate. Moving block In railway signalling, a moving block is a signalling block system where the blocks are defined in real time by computers as safe zones around each train. This requires both knowledge of

432-399: A much more difficult problem when dealing with a variety of different train types, train lengths, and locomotive hauled trains (as opposed to Multiple Units). The only way a moving block system knows where a train is, is from the train's own identification of where it is. Traditionally signalling systems use external means, such as axle counters and track circuits to determine the location of

480-586: A railway junction as a junction station . In the UK it is customary for the junction (and the related station) to be named after the next station on the branch, e.g. Yeovil Junction is on the mainline railway south of Yeovil , and the next destination on the branch is Yeovil Pen Mill . Frequently, trains are built up and taken apart (separated) at such stations so that the same train can be divided and proceed to multiple destinations. For goods trains (US: freight trains), marshalling yards (US: Classification yards ) serve

528-425: A series of transponders in the rail corridor that each have a known location. When a train traverses over a transponder, it will receive the identification information allowing the train to know precisely where on the network it is. Because trains also have the ability to determine their own speed, this information can be combined and transmitted to the external signalling computer (at a rail operations centre). Using

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576-664: A similar purpose. The capacity of the junctions limits the capacity of a railway network more than the capacity of individual railway lines . This applies more as the network density increases. Measures to improve junctions are often more useful than building new railway lines. The capacity of a railway junction can be increased with improved signaling measures, by building points suitable for higher speeds, or by turning level junctions into flying junctions , where tracks are grade-separated , and so one track passes over or under another. With more complicated junctions such construction can rapidly become very expensive, especially if space

624-485: A single track with passing loops poses operational problems, because of the different demands of freight operators and public transport. In many smaller countries passenger operations are done during the day, while freight trains operate mostly during the night. Dedicated tracks have been assigned to some operations. Inactive locomotives may be housed in a locomotive depot (UK term) or engine house, also known as an engine shed or roundhouse (US). In engine facilities , or

672-460: A station means trains won't travel anywhere near as close to each other on 95% of the railway as they technically would be able to, if there were no stations. Consider that a two-track railway with four parallel platforms (2 per direction) at stations can have more or less double the frequency of the same line, but with only two platforms at stations (one per direction) even if both lines use equivalent signalling systems. This reality means that most of

720-416: A train. What this means is that most trains have no way of positively confirming that the entire train is still connected. Such systems can easily be added to multiple unit passenger trains, especially if they are very rarely separated, but the implementation of technology to do the same with locomotive hauled trains is significantly more involved. Every effective solution would require expensive technology,

768-592: Is and how fast it is moving. With moving block, lineside signals are not provided, and instructions are passed directly to the trains. It has the advantage of increasing track capacity by allowing trains to run much closer together. The system is only used on very few independent networks such as underground lines. Most rail systems serve a number of functions on the same track, carrying local, long-distance and commuter passenger trains, and freight trains. The emphasis on each varies by country. Some urban rail transit , rapid transit and light rail systems are isolated from

816-431: Is considered obsolete by being outdated or inefficient when compared to newer equipment, or by being worn to a point that is un-repairable, may be taken out of railroad service. These pieces of equipment may have usable parts removed by the railroad company for reuse on other machines, or may be sold as complete units for reconditioning and reuse by another user. If the equipment is considered completely un-serviceable, and it

864-488: Is currently considered unsafe. Instead, the advantage of Moving block systems generally is that of decreased lineside equipment, which can save money in comparison to achieving the same headway capacity using the large amount of additional equipment it would take to do it with fixed or virtual block systems. Moving block is in use on several London Underground lines, including the Jubilee , and Northern lines, and parts of

912-584: Is financially unwise to attempt to make it so, the entire machine may be declared scrap and is usually sold to be taken away and dismantled for recycling of the raw materials. If the process of salvage or scrapping is financially unrecoverable, the equipment may be left in place until it becomes possible to do so. In some cases a significant or desirable piece of equipment will be purchased for preservation. There units may be placed in railway museums or may be purchased by railway preservation groups or private collectors. Steam locomotives were frequently housed in

960-497: Is in fact how the Moscow Metro , and London Underground Victoria Line operate. They do not have moving blocks, merely a very high number of closely spaced "virtual" blocks. These networks are often considered to be two of the highest capacity railway lines in the world. The second reason why capacity is not necessarily improved, is because trains operating on a railway line with stations must make station stops. This time spent in

1008-509: Is not technically a standard, rather it is a concept that can be implemented through multiple standards. CBTC is the most common associated standard, however CBTC as it is described in IEEE 1474 (1999) makes no mention of a requirement for moving block operation. That said, the overwhelming majority of moving block systems use a signalling system consistent with the IEEE 1474 (1999) standard. Many different manufactures create systems consistent with

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1056-416: Is produced by various manufactures, but this standard has protocols and therefore all ETCS equipment is compatible, unlike CBTC systems. Theoretically moving block can provide capacity advantages compared to fixed block systems, however in practice such advantages are difficult to fully realise. The main reason for this is a combination of the way railway networks practically operate, and tolerances within

1104-449: Is restricted by tunnels , bridges or inner-city tracks. The installation of junctions into a rail system poses many challenges, including increased maintenance costs, and problems in on-time performance. Metro rail systems have a rail network design where the number of junctions is minimized. Passengers, and not trains, move from one train station to another. Rail transport operations Rail transport operations are

1152-428: Is sent as packages of information on the order of several times per second, to as infrequently as several seconds between transmissions. What this means is in practice, is that movement authority is given as several metre sections at a time, often with a buffer and a slight delay from the actual position of the train ahead. Therefore, a similar level of performance could be achieved using fixed, but very small blocks. This

1200-602: Is the signalling protocol for the European Rail Traffic Management System (ERTMS). This system is commonly known to have three levels: Level 1 (an ATP system only); Level 2 (a virtual block system that can also be provided with Automatic Train Operation (ATO)); and Level 3 (similar to Level 2 but uses moving block and can do away with a lot of the lineside equipment. In practice level 3 is not yet used, and this has become an extension of Level 2. Equipment

1248-678: The East Rail line . It was supposed to be the enabling technology on the modernisation of Britain's West Coast Main Line which would allow trains to run at a higher maximum speed (140 mph or 230 km/h), but the technology was deemed not mature enough, considering the large number of junctions on the line, and the plan was dropped. Current implementations of Moving block have only been effectively proven on segregated networks with few junctions. The European Rail Traffic Management System 's level-3 specification (naming on this has recently changed) for

1296-604: The Hong Kong MTR and at some stations, under certain conditions on the New York City Subway 's BMT Canarsie Line ( L train), however there is no verification of this available. Additionally, if it was permissible to give the following train movement authority past the rear of the leading train (up to the point where the rear of the leading train would end up if its emergency brakes were applied) capacity could be further increased. However, this has never been done and

1344-452: The "moving block" concept. Each time a train passes a transponder, it re-calibrates the location allowing the system to retain accuracy. Technologically, the three most difficult parts to achieve a moving block railway system are: Moving block signalling could not effectively be implemented until the invention of reliable systems to communicate both ways between a train and a signalling system. While such technically has existed for decades,

1392-543: The IEEE 1474 standard, and very few of them (if any) are compatible with each other. Transmission-based Train Control (TBTC) is an earlier form of CBTC that used induction loops on the track for communication with the signalling system, rather than radio signals or some other method. The words Transmission and Communication and synonyms in some circumstances, so neither one of these names accurately describes what each standard is. List of systems considered to use TBTC are: ETCS

1440-406: The benefits of a moving block signalling system can only be achieved in and around stations. However, then consider that almost all railways have an operational requirement that a following train cannot begin to enter the train platform, until the rear of the previous train has completely departed. This acts as a "fixed" block even on moving block systems, and will necessarily limit the throughput of

1488-424: The cost of which may outweigh the benefits of a moving block system. Another version of the moving block system would be to locate computers solely on the trains themselves. Each train determines its location in relation to all the other trains and sets its safe speeds using this data. Less wayside equipment is required compared to the off-train system but the number of transmissions is much greater. "Moving block"

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1536-431: The day-to-day operations of a railway. A railway has two major components: the infrastructure (the permanent way , tracks, stations, freight facilities, viaducts, tunnels, etc.) and the rolling stock (the passenger coaches , locomotives, freight cars , etc.) Ownership and operation of these two components varies by location. In some places (notably, most of North America) private railway companies own and operate both

1584-518: The exact location and speed of all trains at any given time, and continual communication between the central signalling system and the train's cab signalling system. Moving block allows trains to run closer together (reduced headway ) while maintaining required safety margins, thereby increasing the line's overall capacity. It may be contrasted with fixed block signalling systems. Communications Based Train Control (CBTC) and Transmission Based Signalling (TBS) are two signalling standards that can detect

1632-608: The exact location of trains and to transmit back the permitted operating speed to enable this flexibility. The European Train Control System ( ETCS ) also has the technical specifications to allow moving block operations, though no system is uses it currently, besides test tracks. Information about train location can be gathered through active and passive markers along the tracks, and train-borne tachometers and speedometers. Satellite-based systems are not used because they do not work in tunnels. Traditionally, moving block works by having

1680-523: The impracticality of early technology a system made it unviable for many years. Pulse codes were used on the first version of the London Underground Victoria line 's signalling system. However, a pulse code two-way communication system using the computational technology at the time would have been complicated, so a fixed block system was used instead. Train integrity, while not a complicated problem on short suburban and metro lines, becomes

1728-456: The infrastructure and rolling stock (for example, Union Pacific ). In the United Kingdom, the infrastructure is owned and maintained by Network Rail while rolling stock is largely owned and operated by private railway companies. In countries with nationalized rail systems such as China and France , both the infrastructure and rolling stock are owned and operated directly or indirectly by

1776-411: The intrinsic nature of the system. The slope at which trains run must also be calculated correctly. In this stage, it is decided where tunnels pass. Rail transport systems affect the human geography. Large cities (such as Nairobi ) may be founded by a railroad passing through. Historically, when a station has been built outside the town or city it is intended to serve, that town has expanded to include

1824-443: The line to only that which is possible using conventional signalling practices. Most of the benefit networks gain from using moving block actually comes from the increased consistency of train movement, one gets from ATO . However, ATO is possible even without moving block. Moving block can increase the capacity of a line if this limitation is removed from the system, which purportedly has been done on some railway networks, such as

1872-486: The moving block system. While a moving block system can technically allow a train to get as close as it can to the train in front while still retaining enough space for it to be able to stop (using regular service brakes) should a further update to the movement authority not be received, in practice if a train was to drive this close to the train ahead, the tiny inconsistency between the movement authority updates would require frequent braking applications and likely result in

1920-781: The national government. The operation of the railway is through a system of control, originally by mechanical means, but nowadays more usually electronic and computerized . Signalling systems used to control the movement of traffic may be either of fixed block or moving block variety. Most blocks are 'fixed' blocks, i.e. they delineate a section of track between two defined points. On timetable, train order, and token-based systems, blocks usually start and end at selected stations. On signalling-based systems, blocks usually start and end at signals . Alternatively, cab signalling may be in use. The lengths of blocks are designed to allow trains to operate as frequently as necessary. A lightly used branch line might have blocks many kilometres long, whilst

1968-399: The national system in the cities they serve. Some freight lines serving mines are also isolated, and these are usually owned by the mine company. An industrial railway is a specialized rail system used inside factories or mines. Steep grade railways are usually isolated, with special safety systems. The permanent way trails through the physical geography. The tracks' geometry is limited by

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2016-498: The passenger cars. Most public transport passenger operations happen in the train station and in the passenger car . The passenger buys a ticket , either in the station, or on the train (sometimes at a higher fare ). There are generally speaking two ways of validating a ticket: Some passenger cars, especially in long-distance high-speed trains, have a restaurant or bar. These need to be catered. In recent times, train catering has been diminished somewhat by vending machines in

2064-583: The physical geography. Trains are pushed/pulled by one or more locomotive units. Two or more locomotives coupled in multiple traction are frequently used in freight trains. Railroad cars or rolling stock consist of passenger cars , freight cars , maintenance cars and in America cabooses . Modern passenger trains sometimes are pushed/pulled by a tail and head unit (see top and tail ), of which not both need to be motorised or running. Many passenger trains consist of multiple units with motors mounted beneath

2112-496: The specifications of each particular system. Rail transport systems are built into the landscape , including both the physical geography (hills, valleys, etc.) and the human geography (location of settlements). The rail transport system may in turn feedback into the human geography. The permanent way of a system must pass through the geography and geology of its region. This may be flat or mountainous, may include obstacles such as water and mountains. These determine, in part,

2160-651: The station, or buildings (especially Inns ) sprung up near the station. The existence of a station may increase the number of commuters who live in a town or village and so cause it to become a dormitory town . The transcontinental railroad was a large factor in American colonization of the Western frontier . China's railroad expansion into Tibet may have similar consequences. Rail transport systems are often used for purposes they were not designed for, but have evolved into due to changes in human geography. Politics can play

2208-585: The sub-surface lines . In London it is also used on the Docklands Light Railway and the core section of the Elizabeth line . New York City Subway 's BMT Canarsie Line ( L train), Tren Urbano (Puerto Rico), Singapore's MRT , and Vancouver's SkyTrain , also employ moving block signalling. It is also used by the Hong Kong MTR , on the Tuen Ma line , Disneyland Resort line , South Island line and

2256-431: The train naturally tending to travel further behind. Most moving block systems also operate with a buffer to account for this, so trains might be 10 to 30 metres off the ideal, or "perfect" positioning. This helps to account for the transmission delays, and the slight inconsistency in train positioning calculations. Additionally, transmission between the train and the signalling system isn't literally continuous, instead it

2304-633: The train station or on the train. When not in use, passenger cars are stored, maintained and repaired in coach yards . Freight or cargo trains are loaded and unloaded in intermodal terminals (also called container freight stations or freight terminals), and at customer locations (e.g. mines , grain elevators , factories ). Intermodal freight transport uses standardized containers , which are handled by cranes . Along their routes, freight trains are routed through rail yards to sort cars and assemble trains for their final destinations, as well as for equipment maintenance, refueling, and crew changes. Within

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