Metro
- This page refers to urban rail mass transit systems. For other uses see metro (disambiguation).
Underground,
subway and
metro are common names for a form of
mass transit public transport system employing
trains. In many cases, at least a portion of the rails are placed in
tunnels dug beneath the surface of a city.
[1]
A person with a devoted interest in these systems is a
metrophile.
Definition and nomenclature
One definition of a "true" metro system is as follows:
- an urban, electric mass transit system\n#totally independent from other traffic\n#with high service frequency.
Those who prefer the American term "subway" or the British "underground"\nwould additionally specify that at least the most important, central parts\nof the system must be located below street level; those who prefer "metro"\ntend to view this as a less important characteristic and are pleased to\ninclude systems that are entirely elevated or at grade. In some cities\n"subway" refers to the entire system, in others only to the portions that actually are underground.
For a more comprehensive listing of other names of this kind of system in cities around the world, see the list of metro systems. Germanic languages\ngenerally use names meaning "underground railway", while many others use\n"metro".
Importance and functions
The volume of passengers a metro train can carry is often quite high, and a metro system is often viewed as the backbone of a large city's public transportation system.
Most underground systems are for public transportation, but a few cities\nhave built freight (Chicago Freight Subway) or postal lines. One example was the Post Office Railway, which transported mail underground between sorting offices in London from 1927 until it was "mothballed" in 2003. During the Cold War an important secondary function of some underground systems was to provide shelter in case of a nuclear attack.
\nMetro systems have often been used to showcase economical, social, and technological achievements of a nation, especially in the Soviet Union and other socialist countries. With their marble walls, polished granite floors and splendid mosaics, the metro systems of Moscow and St. Petersburg are widely regarded as some of the most beautiful in the world. Modern metro stations in Russia are usually still built with the same emphasis on appearance.
Metro trains
Some metro systems are built to the full size of main-line railways;\nothers use smaller tunnels, restricting the size and sometimes the shape\nof the trains (in London the informal term\ntube train is commonly used), or use light rail rolling stock.\nThe trains usually stop at frequent intervals to let passengers on or off.
Drivers and automation
Traditionally, metro trains are driven by human drivers, but automated trains also exist, in, for example, London (the Victoria Line), Singapore, and Paris. This is not a recent invention; operation of trains on the Victoria Line has been automatic since its opening in 1968. However, in common with most systems, an operator is still carried in a cab at the front of the train. The VAL (véhicule automatique léger) of Lille, inaugurated in 1983, provided the first driverless underground system. Other driverless lines now include the line 14 (Meteor) of the Paris Metro, opened in 1998. The Docklands Light Railway (1987) in London, whilst for the most part not underground, is also driverless. Singapore's North-East Line (2003) claims to be the world's first fully automated heavy rail line. See also People mover.
Subway construction
The construction of an underground is an expensive project, often carried out over a number of years. Several modes of tunneling exist. In one common method, known as cut-and-cover, the city streets are excavated and\na tunnel structure strong enough to support the road above is built at the\ntrench, which is then filled in and the roadway rebuilt. This method (used\nfor most of the underground parts of the São Paulo metro, for example)\noften involves extensive relocation of the utilities commonly buried not\nfar below city streets -- particularly power and\ntelephone wiring,\nwater and gas mains, and sewers.\nThe structures are typically made of concrete, perhaps with\nstructural columns of steel; in the oldest systems, brick and\ncast iron were used.
Another usual way is to start with a vertical shaft and then dig the tunnels\nhorizontally from there, often with a tunnelling shield, thus avoiding\nalmost any disturbance to existing streets, buildings, and utilities.\nBut problems with ground water are more likely, and tunnelling through\nnative bedrock may require blasting. (The first city to extensively\nuse deep tunneling was London, where a thick sedimentary layer of\nclay largely avoids both problems.) The confined space in the tunnel\nalso limits the machinery that can be used, but specialized\ntunnel-boring machines are now available to overcome this challenge. One disadvantage with this, however, is that the cost of tunnelling is much higher than building systems cut-and-cover, at-grade or elevated.
The deepest metro system in the world was built in St. Petersburg, Russia. In this city, built in the marshland, stable soil starts more than 50 meters deep. Above that level the soil moslty consists of water-bearing finely dispersed sand. Because of this, only 3 stations out of nearly 60 are built near the ground level and 3 more above the ground. Many stations lie as deep as 100 meters below the surface. However, the location of the world deepest station is not as clear. Among the possible candidates are:\n*Admiraltejskaya, Proletarskaya and Komendantskij Prospekt stations in St. Petersburg (currently not operational)\n*Arsenalnaya station in Kiev, Ukraine (built under a hill)\n*Park Pobedy station in Moscow Metro (built under a hill)\n*Puhung station in Pyongyang, North Korea (the Pyongyang metro doubles as a nuclear shelter)
One advantage of deep tunnels is that they can dip in a basin-like profile\nbetween stations, without incurrent significant extra costs due to having\nto dig deeper. This technique, also referred to as putting stations "on humps",\nallows gravity to assist the trains as they accelerate from one station and\nbrake at the next. It was used as early as 1890 on parts of the\nCity and South London Railway, and has been used many times since.
Underground systems use a variety of technologies. Most systems run on steel wheels and rails, although a number of modern systems use rubber tires and concrete rollways. (The Montreal metro was the first completely rubber-tired metro system.) Power is usually supplied either by means of a single third rail (New York), but some systems use two live rails (London) or overhead lines (Madrid). Systems may be underground, at grade, elevated, or a mix as in the Paris metro. Some systems use light rail; other cities' systems are hybrids wherein a tramway moves underground in the city centre.
Due to the complexity of construction and operations, underground systems need constant investment from the public authority, to avoid disasters like King's Cross fire in London's Underground.
History
In 1844 the Long Island Rail Road opened the Atlantic Avenue Tunnel, carrying its line for about 500 m under the streets of Brooklyn (now part of New York City). Although sometimes called the "world's oldest subway tunnel", this had no stations and was used for long-distance as well as suburban trains.
The first real underground line in the sense discussed here was the\nMetropolitan Railway in London, which opened\nin 1863, using condensing steam locomotives as no better motive power\nwas available. It was an immediate success and many extensions followed;\nthe Metropolitan eventually became an important part of the London Underground system. Steam working underground lasted until 1905.
In 1870 short single-track lines opened in both New York and London using alternative technologies. In New York, Alfred Beach built a 95 m tunnel (with a single station and a dead end at the other end) to demonstrate pneumatic train operation; this operated until 1873, after which the tunnel became a rifle range and was then abandoned. In London, the Tower Subway provided a crossing under the River Thames using a tiny cable car for the 410 m journey; the line closed in a matter of months and the tunnel was given over to pedestrians, later becoming a utility conduit.
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The first deep-level underground line was the City and South London Railway, which opened in 1890. Steam operation being considered ridiculous, cable traction was chosen; but during construction the management decided to try electric locomotives instead, and so the C&SLR became the first underground electric railway and the first important electric railway of any kind.
The first line of the Paris Metro opened in 1900. Its full name\nwas the Chemin de Fer Métropolitain, a direct translation of London's\nMetropolitan Railway. The name was shortened to metro in French, and this word was borrowed by many other languages.
Boston has the oldest subway system in the United States, the green line. Later lines carried full-size trains rather\nthan trams. The first section of the New York Subway, which became the world's largest (by some measures), did not open until 1904.
The oldest underground in Latin America was built in 1913 in Buenos Aires.
The Toronto subway (1953) was the first to replace street transit routes. Toronto also developed the aluminum subway car, which reduced operating costs.
In Brazil, the first underground opened in 1974 in São Paulo, and and now carries some 4 million passengers on an average week day. Part of it consists of converted older railways; some of its stations actually date from the 1880's. Underground lines have been built also in Rio de Janeiro, Belo Horizonte, Recife, Porto Alegre and Brasília.
Asia's oldest subway line is Tokyo's Ginza Line, opened in 1927.
See also
External links
\n* UrbanRail.Net (formerly called metroPlanet) - descriptions of all metro systems in the world, each with a schematic map showing all stations.\n* Comparison of world subway systems at the same scale.\n* "Mind the Gap".\n* Memoirs of a subway musician This musician played in the subway stations of NYC, Paris, Prague & Rome.
\nCategory:Metro\n
