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Rapid transit technology is technology used for public, mass rapid transit. Such transit is commonly known as a Metro or Subway, and it has undergone significant changes in the years since the Metropolitan Railway opened publicly in London in 1863. [1] [2]
Some urban rail lines are built to a loading gauge as large as that of main-line railways; others are built to smaller and have tunnels that restrict the size and sometimes the shape of the train compartments. One example is the London Underground which has acquired the informal term "tube train" due to its cylindrical cabin shape.
In many cities, metro networks consist of lines operating different sizes and types of vehicles. Although these sub networks are not often connected by track, in cases when it is necessary, rolling stock with a smaller loading gauge from one sub network may be transported along other lines that use larger trains.
Although initially the trains of what is now the London Underground were drawn by steam engines, virtually all metro trains, both now and historically, use electric power and are built to run as multiple units. Power for the trains, referred to as traction power, usually takes one of two forms: an overhead line, suspended from poles or towers along the track or from structure or tunnel ceilings, or a third rail mounted at track level and contacted by a sliding "pickup shoe". The practice of sending power through rails on the ground is mainly due to the limited overhead clearance of tunnels, which physically prevents the use of overhead wires. The use of overhead wires allows higher power supply voltages to be used. Although overhead wires are more likely to be used on metro systems without many tunnels, an example of which is the Shanghai Metro, overhead wires are employed on some systems that are predominantly underground, as in Barcelona, Fukuoka, Madrid, and Shijiazhuang. Both overhead wire and third-rail systems usually use the running rails as the return conductor, but some systems use a separate fourth rail for this purpose. There are transit lines that make use of both rail and overhead power, with vehicles able to switch between the two such as Blue Line in Boston.
Most rapid transit systems use conventional standard gauge railway track. Since tracks in subway tunnels are not exposed to rain, snow, or other forms of precipitation, they are often fixed directly to the floor rather than resting on ballast, such as normal railway tracks.
An alternate technology, using rubber tires on narrow concrete or steel roll ways, was pioneered on certain lines of the Paris Métro, and the first completely new system to use it was in Montreal, Canada. On most of these networks, additional horizontal wheels are required for guidance, and a conventional track is often provided in case of flat tires and for switching. There are also some rubber-tired systems that use a central guide rail, such as the Sapporo Municipal Subway and the NeoVal system in Rennes, France. Advocates of this system note that it is much quieter than conventional steel-wheeled trains, and allows for greater inclines given the increased traction of the rubber tires.
Some cities with steep hills incorporate mountain railway technologies in their metros. One of the lines of the Lyon Metro includes a section of rack (cog) railway, while the Carmelit, in Haifa, is an underground funicular.
For elevated lines, another alternative is the monorail, which can be built either as straddle-beam monorails or as a suspended monorail. While monorails have never gained wide acceptance outside Japan, there are some such as Chongqing Rail Transit's monorail lines which are widely used in a rapid transit setting.
In the early days of underground railways, at least two staff members were needed to operated each train: one or more attendants (also called "conductor" or "guard") to operate the doors or gates, as well as a driver (also called the "engineer" or "motorman"). The introduction of powered doors around 1920 permitted crew sizes to be reduced, and trains in many cities are now operated by a single person. Where the operator would not be able to see the whole side of the train to tell whether the doors can be safely closed, mirrors or closed-circuit TV monitors are often provided for that purpose.
A replacement system for human drivers became available in the 1960s, with the advancement of computerized technologies for automatic train control and, later, automatic train operation (ATO). ATO could start a train, accelerate to the correct speed, and stop automatically in the correct position at the railway platform at the next station, while taking into account the information that a human driver would obtain from lineside or cab signals. The first metro line to use this technology in its entirety was London's Victoria line, opened in 1968. In normal operation, a crew member sits in the driver's position at the front, but is only responsible for closing the doors at each station. By pressing two "start" buttons the train would then move automatically to the next station. This style of "semi-automatic train operation" (STO), known technically as "Grade of Automation (GoA) 2", has become widespread, especially on newly built lines like the BART network in the San Francisco Bay Area.
A variant of ATO, "driverless train operation" (DTO) or technically "GoA 3", is seen on some systems, as in London's Docklands Light Railway, which opened in 1987. Here, a "passenger service agent" (formerly called "train captain") would ride with the passengers rather than sit at the front as a driver would, but would have the same responsibilities as a driver in a GoA 2 system. This technology could allow trains to operate completely automatically with no crew, just as most elevators do. When the initially increasing costs for automation began to decrease, this became a financially attractive option for employers. At the same time, countervailing arguments stated that in an emergency situation, a crew member on board the train would have possibly been able to prevent the emergency in the first place, drive a partially failed train to the next station, assist with an evacuation if needed, or call for the correct emergency services and help direct them to the location where the emergency occurred. In some cities, the same reasons are used to justify a crew of two rather than one; one person drives from the front of the train, while the other operates the doors from a position farther back, and is more conveniently able to assist passengers in the rear cars. An example of the presence of a driver purely due to union opposition is the Scarborough RT line in Toronto.
Completely unmanned trains, or "unattended train operation" (UTO) or technically "GoA 4", are more accepted on newer systems where there are no existing crews to be displaced, and especially on light metro lines. One of the first such systems was the VAL (véhicule automatique léger or "automated light vehicle"), first used in 1983 on the Lille Metro in France. Additional VAL lines have been built in other cities such as Toulouse, France, and Turin, Italy. Another system that uses unmanned trains is Bombardier's Innovia Metro, originally developed by the Urban Transportation Development Corporation as the Intermediate Capacity Transit System (ICTS). It was later used on the SkyTrain in Vancouver, British Columbia, which carries no crew members, and the Kelana Jaya Line in Kuala Lumpur, Malaysia.
Systems which use automatic trains also commonly employ full-height platform screen doors or half-height automatic platform gates in order to improve safety and ensure passenger confidence, but this is not universal, as networks like Nuremberg do not, using infrared sensors instead to detect obstacles on the track. Conversely, some lines which retain drivers or manual train operation nevertheless use PEDs, notably London's Jubilee Line Extension. The first network to install PSDs on an already operational system was Hong Kong's MTR, followed by the Singapore MRT.
As for larger trains, the Paris Métro has human drivers on most lines but runs automated trains on its newest line, Line 14, which opened in 1998. The older Line 1 was subsequently converted to unattended operation by 2012, and it is expected that Line 4 will follow by 2019. The North East MRT Line in Singapore, which opened in 2003, is the world's first fully automated underground urban heavy-rail line. The MTR Disneyland Resort Line is also automated, along with trains on the future South Island Line.
The construction of an underground metro is an expensive project and is often carried out over a number of years. There are several different methods of building underground lines.
In one common method, known as cut-and-cover the city streets are excavated and a tunnel structure strong enough to support the road above is built in the trench, which is then filled in and the roadway rebuilt. This method often involves extensive relocation of utilities commonly buried not far below street level – particularly power and telephone wiring, water and gas mains, and sewers. This relocation must be done carefully, as according to documentaries from the National Geographic Society, one of the causes of the April 22, 1992, explosions in Guadalajara was a mislocated water pipeline. The structures are typically made of concrete, perhaps with structural columns of steel; in the oldest systems, brick, and cast iron were used. Cut-and-cover construction can take so long that it is often necessary to build a temporary roadbed while construction is going on underneath, in order to avoid closing main streets for long periods of time.
Another usual type of tunneling method is called bored tunneling. Here, construction starts with a vertical shaft from which tunnels are horizontally dug, often with a tunneling shield, thus avoiding almost any disturbance to existing streets, buildings, and utilities. But problems with ground water are more likely, and tunneling through native bedrock may require blasting. The first city to extensively use deep tunneling was London, where a thick sedimentary layer of clay largely avoids both problems. The confined space in the tunnel also limits the machinery that can be used, but specialized tunnel-boring machines are now available to overcome this challenge. One disadvantage with this, however, is that the cost of tunneling is much higher than building cut-and-cover systems, at-grade or elevated. Early tunneling machines could not make tunnels large enough for conventional railway equipment, necessitating special low, round trains, such as are still used by most of the London Underground, which cannot install air conditioning on most of its lines because the amount of empty space between the trains and tunnel walls is so small. Other lines were built with cut-and-cover and have since been equipped with air-conditioned trains.
The deepest metro system in the world was built in St. Petersburg, Russia where in the marshland, stable soil starts more than 50 metres (160 ft) deep. Above that level, the soil mostly consists of water-bearing finely dispersed sand. Because of this, only three stations out of nearly 60 are built near ground level and three more above the ground. Some stations and tunnels lie as deep as 100–120 metres (330–390 ft) below the surface. However, the location of the world's deepest station is not clear. Usually, the vertical distance between the ground level and the rail is used to represent the depth. Among the possible candidates are:
One advantage of deep tunnels is that they can dip in a basin-like profile between stations, without incurring the significant extra costs associated with digging near ground level. This technique, also referred to as putting stations "on humps", allows gravity to assist the trains as they accelerate from one station and brake at the next. It was used as early as 1890 on parts of the City and South London Railway and has been used many times since, particularly in Montreal.
The West Island Line, an extension of the MTR Island Line serving western Hong Kong Island, opened in 2015, has two stations (Sai Ying Pun and HKU) situated over 100 metres (330 ft) below ground level, to serve passengers on the Mid-levels. They have several entrances/exits equipped with high-speed lifts, instead of escalators. These kinds of exits have existed in many London Underground stations and other stations in former Soviet Union nations.
The Paris Métro, short for Métropolitain, is a rapid transit system in the Paris metropolitan area, France. A symbol of the city, it is known for its density within the city limits, uniform architecture and unique entrances influenced by Art Nouveau. It is mostly underground and 214 kilometres (133 mi) long. It has 302 stations, of which 62 have transfers between lines. There are 16 lines, numbered 1 to 14 with two lines, 3bis and 7bis, which are named because they started out as branches of Line 3 and Line 7; later they officially became separate lines. Lines are identified on maps by number and colour, with the direction of travel indicated by the terminus.
Light rail transit (LRT) is a form of passenger urban rail transit characterized by a combination of tram and metro features. While its rolling stock is more similar to a traditional tram, it operates at a higher capacity and speed, and often on an exclusive right-of-way.
A rubber-tyred metro or rubber-tired metro is a form of rapid transit system that uses a mix of road and rail technology. The vehicles have wheels with rubber tires that run on rolling pads inside guide bars for traction, as well as traditional railway steel wheels with deep flanges on steel tracks for guidance through conventional switches as well as guidance in case a tyre fails. Most rubber-tyred trains are purpose-built and designed for the system on which they operate. Guided buses are sometimes referred to as 'trams on tyres', and compared to rubber-tyred metros.
The S-train is a type of hybrid urban-suburban rail serving a metropolitan region. Some of the larger S-train systems provide service similar to rapid transit systems, while smaller ones often resemble commuter or even regional rail. They are especially common in Germany and Austria, where they are known as S-Bahn, which in the 1930s was an abbreviation of either Schnellbahn, Stadtbahn or Stadtschnellbahn, depending on the city, but they must not be confused with U-Stadtbahnen. Similar S-train systems exist also in Switzerland known as S-Bahn as well. In Denmark, they are known as S-tog[ˈɛsˌtsʰɔˀw], in the Czech Republic as Esko or S-lines, and northern Italy as Servizio ferroviario followed by either the word "metropolitano" or "suburbano".
The Bucharest Metro is an underground rapid transit system that serves Bucharest, the capital of Romania. It first opened for service on 19 November 1979. The network is run by Metrorex. One of two parts of the larger Bucharest public transport network, Metrorex has an average of approximately 720,000 passenger trips per weekday, compared to the 1,180,000 daily riders on Bucharest's STB transit system. In total, the Metrorex system is 71.35 kilometres (44.3 mi) long and has 51 stations.
A third rail, also known as a live rail, electric rail or conductor rail, is a method of providing electric power to a railway locomotive or train, through a semi-continuous rigid conductor placed alongside or between the rails of a railway track. It is used typically in a mass transit or rapid transit system, which has alignments in its own corridors, fully or almost fully segregated from the outside environment. Third rail systems are always supplied from direct current electricity.
The Stockholm Underground is a rapid transit system in Stockholm, Sweden. The first line opened in 1950, and today the system has 100 stations in use, of which 47 are underground and 53 above ground. There are three coloured main lines on the tube maps. These do however form seven actual routes. Routes numbered 17, 18 and 19, 13 and 14 and 10 and 11 all go through Stockholm City Centre in a very centralized metro system. All seven actual lines use The T-Centralen hub station. Apart from this central station for the metro, there exists just one other interchange between lines, the Fridhemsplan station, although both the green and red lines are mutually accessible at the Slussen and Gamla Stan stations.
The Athens Metro is a rapid-transit system in Greece which serves the Athens conurbation and parts of East Attica. Line 1 opened as a conventional steam railway in 1869 and electrified in 1904. In 1991, Attiko Metro S.A. constructed and extended Lines 2 and 3. It has significantly changed Athens by providing a much-needed solution to the city's traffic and air pollution problem, as well as revitalising many of the areas it serves. An extension of Line 3 is under construction towards Piraeus and also other extensions of existing lines, as well as a new Line 4, are under consideration. The Athens Metro is actively connected with the other means of public transport, such as buses, trolleys, the Athens Tram and the Proastiakos Athens suburban railway. The Athens Metro is hailed for its modernity and many of its stations feature works of art, exhibitions and displays of the archeological remains found during its construction. Photography and video-taking is permitted across the whole network and street photographers often work in Athens Metro.
An elevated railway is a rapid transit railway with the tracks above street level on a viaduct or other elevated structure. The railway may be broad-gauge, standard-gauge or narrow-gauge railway, light rail, monorail, or a suspension railway. Elevated railways are normally found in urban areas where there would otherwise be multiple level crossings. Usually, the tracks of elevated railways that run on steel viaducts can be seen from street level.
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.
Urban rail transit is an all-encompassing term for various types of local rail systems providing passenger service within and around urban or suburban areas. The set of urban rail systems can be roughly subdivided into the following categories, which sometimes overlap because some systems or lines have aspects of multiple types.
Various terms are used for passenger rail lines and equipment-the usage of these terms differs substantially between areas:
Platform screen doors (PSDs) and platform edge doors (PEDs) at train or subway stations separate the platform from the train. They are primarily used for passenger safety. They are a relatively new addition to many metro systems around the world, some having been retrofitted to established systems. They are widely used in newer Asian and European metro systems.
The Chennai Metro is a rapid transit system serving the city of Chennai, Tamil Nadu, India. It is the third largest metro system in India after Delhi Metro and Hyderabad Metro. The system commenced service in 2015 after partially opening the first phase of the project. The network consists of two colour-coded lines covering a length of 45.1 kilometres (28.0 mi). The Chennai Metro Rail Limited (CMRL), a joint venture between Government of India and the Government of Tamil Nadu built and operates the Chennai Metro. The system has a mix of underground and elevated stations and uses standard gauge. The services operate daily between 4:30 and 23:00 with a varying frequency of 5 to 14 minutes. As of November 2019, about 121,000 people use the service on a daily basis. There are 42 trains with four coaches each, making a total of 168 coaches, operating in the first phase.
Sydney, the largest city in Australia, has an extensive network of passenger and freight railways. The passenger system includes an extensive suburban railway network, operated by Sydney Trains, a metro network and a light rail network. A dedicated freight network also exists. Future expansion of the light rail network includes the newly opened CBD and South East Light Rail, and the planned Parramatta Light Rail.
The history of rapid transit began in London with the opening of the Metropolitan Railway, which is now part of the London Underground, in 1863. By World War I, electric underground railways were being used in Athens, Berlin, Boston, Buenos Aires, Budapest, Glasgow, Hamburg, Liverpool, New York City, Paris, and Philadelphia.
Rapid Rail Sdn Bhd was established to place all three rail operators for Sistem Transit Aliran Ringan Sdn Bhd (STAR-LRT), Projek Usahasama Transit Ringan Automatik Sdn Bhd (PUTRA-LRT) and KL Starrail Sdn Bhd – under one administrating umbrella in Kuala Lumpur, Malaysia.
Rapid transit in the United Kingdom consists of five systems in four cities: the London Underground and Docklands Light Railway, Tyne and Wear Metro, the Glasgow Subway and Merseyrail in the Liverpool City Region. Rapid transit has also been proposed in other U.K. cities including Manchester, Birmingham, Bristol, and Cambridge.
The Shiraz Metro is the rapid transit system in Shiraz, Fars, Iran, operated by Shiraz Urban Railway Organization. Construction began in 2001, and service in the first line officially commenced on October 11, 2014.
Rapid transit or mass rapid transit (MRT), also known as heavy rail, metro, subway, tube, U-Bahn or underground, is a type of high-capacity public transport generally found in urban areas. Unlike buses or trams, rapid transit systems are electric railways that operate on an exclusive right-of-way, which cannot be accessed by pedestrians or other vehicles of any sort, and which is often grade separated in tunnels or on elevated railways.