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Rapid transit or mass rapid transit (MRT), also known as heavy rail or metro, is a type of high-capacity public transport generally found in urban areas. A rapid transit system that primarily or traditionally runs below the surface may be called a subway, tube, or underground. Unlike
bus A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle that carries significantly more passengers than an average car or van. It is most commonly used in public transport, but is also in use for cha ...
es or trams, rapid transit systems are railways (usually electric) that operate on an exclusive right-of-way, which cannot be accessed by pedestrians or other vehicles, and which is often
grade-separated In civil engineering (more specifically highway engineering), grade separation is a method of aligning a junction of two or more surface transport axes at different heights (grades) so that they will not disrupt the traffic flow on other tran ...
in tunnels or on elevated railways. Modern services on rapid transit systems are provided on designated lines between
stations Station may refer to: Agriculture * Station (Australian agriculture), a large Australian landholding used for livestock production * Station (New Zealand agriculture), a large New Zealand farm used for grazing by sheep and cattle ** Cattle statio ...
typically using
electric multiple unit An electric multiple unit or EMU is a multiple-unit train consisting of self-propelled carriages using electricity as the motive power. An EMU requires no separate locomotive, as electric traction motors are incorporated within one or a numbe ...
s on
rail track A railway track (British English and UIC terminology) or railroad track (American English), also known as permanent way or simply track, is the structure on a railway or railroad consisting of the rails, fasteners, railroad ties (sleepers, ...
s, although some systems use guided rubber tires, magnetic levitation ('' maglev''), or monorail. The stations typically have high platforms, without steps inside the trains, requiring custom-made trains in order to minimize gaps between train and platform. They are typically integrated with other public transport and often operated by the same public transport authorities. However, some rapid transit systems have at-grade intersections between a rapid transit line and a road or between two rapid transit lines. The world's first rapid transit system was the partially underground
Metropolitan Railway The Metropolitan Railway (also known as the Met) was a passenger and goods railway that served London from 1863 to 1933, its main line heading north-west from the capital's financial heart in the City to what were to become the Middlesex su ...
which opened in 1863 using
steam locomotive A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material (usually coal, oil or, rarely, wood) to heat water in the locomot ...
s, and now forms part of the London Underground. In 1868, New York opened the elevated
West Side and Yonkers Patent Railway The IRT Ninth Avenue Line, often called the Ninth Avenue Elevated or Ninth Avenue El, was the first elevated railway in New York City. It opened on July 3, 1868 as the West Side and Yonkers Patent Railway, as an experimental single-track cable ...
, initially a cable-hauled line using static
steam engine A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be trans ...
s. ,
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
has the largest number of rapid transit systems in the world—40 in number, running on over of track—and was responsible for most of the world's rapid-transit expansion in the 2010s. The world's longest single-operator rapid transit system by route length is the
Shanghai Metro The Shanghai Metro (; Shanghainese: ''Zaon6he5 Di6thiq7'') is a rapid transit system in Shanghai, operating urban and suburban transit services to 14 of its 16 municipal districts and to Kunshan, Jiangsu Province. Served as a part of Shangha ...
. The world's largest single rapid transit service provider by number of stations (472 stations in total) is the
New York City Subway The New York City Subway is a rapid transit system owned by the government of New York City and leased to the New York City Transit Authority, an affiliate agency of the state-run Metropolitan Transportation Authority (MTA). Opened on October 2 ...
. The three busiest rapid transit systems in the world by annual ridership are the
Shanghai Metro The Shanghai Metro (; Shanghainese: ''Zaon6he5 Di6thiq7'') is a rapid transit system in Shanghai, operating urban and suburban transit services to 14 of its 16 municipal districts and to Kunshan, Jiangsu Province. Served as a part of Shangha ...
, Tokyo subway system and the Moscow Metro.


Terminology

''Metro'' is the most common term for underground rapid transit systems used by non-native English speakers. Rapid transit systems may be named after the medium by which passengers travel in busy
central business district A central business district (CBD) is the commercial and business centre of a city. It contains commercial space and offices, and in larger cities will often be described as a financial district. Geographically, it often coincides with the "city ...
s; the use of tunnels inspires names such as ''subway'', ''underground'', ''Untergrundbahn ( U-Bahn)'' in German,White, 2002: 63 or the ''Tunnelbana (T-bana)'' in Swedish;Ovenden, 2007: 93 the use of
viaduct A viaduct is a specific type of bridge that consists of a series of arches, piers or columns supporting a long elevated railway or road. Typically a viaduct connects two points of roughly equal elevation, allowing direct overpass across a wide v ...
s inspires names such as ''elevated'' (''L'' or ''el''), ''skytrain'',
Ovenden Ovenden is a village in West Yorkshire, England, next to Boothtown and Illingworth about a mile from Halifax town centre. It is also a Calderdale Ward whose population at the 2011 Census was 12,351. Ovenden railway station on the Halifax and ...
, 2007: 16
''overhead'', ''overground'' or ''Hochbahn'' in German. One of these terms may apply to an entire system, even if a large part of the network (for example, in outer suburbs) runs at ground level. In most of Britain, a ''subway'' is a pedestrian underpass; the terms ''Underground'' and ''Tube'' are used for the London Underground, and the North East England Tyne and Wear Metro, mostly overground, is known as the ''Metro''. In Scotland, however, the
Glasgow Subway The Glasgow Subway is an underground light metro system in Glasgow, Scotland. Opened on 14 December 1896, it is the fourth-oldest underground rail transit system in Europe after the London Underground, Liverpool's Mersey Railway and the Budapes ...
underground rapid transit system is known as the ''Subway''. Various terms are used for rapid transit systems around
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
. The term ''metro'' is a shortened reference to a
metropolitan area A metropolitan area or metro is a region that consists of a densely populated urban agglomeration and its surrounding territories sharing industries, commercial areas, transport network, infrastructures and housing. A metro area usually com ...
. Rapid transit systems such as the
Washington Metro The Washington Metro (or simply Metro), formally the Metrorail,Google Books search/preview
,
Los Angeles Metro Rail The Los Angeles Metro Rail is an urban rail transit system serving Los Angeles County, California, United States. It consists of seven lines, including five light rail lines (the A Line (Los Angeles Metro), A, C Line (Los Angeles Metro), C, E Li ...
, the
Miami Metrorail Metrorail is the heavy rail rapid transit system of Miami and Miami-Dade County in the U.S. state of Florida. Metrorail is operated by Miami-Dade Transit (MDT), a departmental agency of Miami-Dade County. Opened in 1984, it is Florida's only ra ...
, and the
Montreal Metro The Montreal Metro (french: Métro de Montréal) is a rubber-tired underground rapid transit system serving Greater Montreal, Quebec, Canada. The metro, operated by the Société de transport de Montréal (STM), was inaugurated on October 14, ...
are generally called the ''Metro''. In Philadelphia, the term “El” is used for the Market–Frankford Line which runs mostly on an elevated track, while the term “subway” applies to the Broad Street Line which is almost entirely underground. Chicago's commuter rail system that serves the entire metropolitan area is called '' Metra'' (short for "Metropolitan Rail"), while its rapid transit system that serves the city is called the "L". Boston's subway system is known locally as "The T", while in the San Francisco Bay Area, residents refer to
Bay Area Rapid Transit Bay Area Rapid Transit (BART) is a rapid transit system serving the San Francisco Bay Area in California. BART serves 50 stations along six routes on of rapid transit lines, including a spur line in eastern Contra Costa County which uses ...
by its acronym "BART". The
New York City Subway The New York City Subway is a rapid transit system owned by the government of New York City and leased to the New York City Transit Authority, an affiliate agency of the state-run Metropolitan Transportation Authority (MTA). Opened on October 2 ...
is referred to simply as “the subway”, despite 40% of the system running above ground. The term “L” or “El” is not used for elevated lines in general as the lines in the system are already designated with letters and numbers. The “L” train or L (New York City Subway service) refers specifically to the 14th Street–Canarsie Local line, and not other elevated trains. In most of Southeast Asia and in Taiwan, rapid transit systems are primarily known by the acronym ''MRT''. The meaning however varies from one country to another. In Indonesia, the acronym stands for '' Moda Raya Terpadu'' or ''Integrated Mass ransitMode'' in English. In the Philippines, it stands for '' Metro Rail Transit'', with two
lines Line most often refers to: * Line (geometry), object with zero thickness and curvature that stretches to infinity * Telephone line, a single-user circuit on a telephone communication system Line, lines, The Line, or LINE may also refer to: Arts ...
also using the term ''subway'' being underground lines. In Thailand, it stands for ''
Metropolitan Rapid Transit The Metropolitan Rapid Transit or MRT is a mass rapid transit system serving the Bangkok Metropolitan Region in Thailand. The MRT system comprises two rapid transit lines, with a further three lines (one rapid transit line and two monorail lines) ...
'', and previously also used the ''Mass Rapid Transit'' name. Outside of Southeast Asia,
Kaohsiung Kaohsiung City (Mandarin Chinese: ; Wade–Giles: ''Kao¹-hsiung²;'' Pinyin: ''Gāoxióng'') is a special municipality located in southern Taiwan. It ranges from the coastal urban center to the rural Yushan Range with an area of . Kaohsi ...
and Taoyuan, Taiwan have their own ''MRT'' systems which also stands for ''Mass Rapid Transit'' as with Singapore.


History

The opening of London's steam-hauled
Metropolitan Railway The Metropolitan Railway (also known as the Met) was a passenger and goods railway that served London from 1863 to 1933, its main line heading north-west from the capital's financial heart in the City to what were to become the Middlesex su ...
in 1863 marked the beginning of rapid transit. Initial experiences with steam engines, despite ventilation, were unpleasant. Experiments with
pneumatic railway An atmospheric railway uses differential air pressure to provide power for propulsion of a railway vehicle. A static power source can transmit motive power to the vehicle in this way, avoiding the necessity of carrying mobile power generating eq ...
s failed in their extended adoption by cities. Electric traction was more efficient, faster and cleaner than steam and the natural choice for trains running in tunnels and proved superior for elevated services. In 1890, the
City & South London Railway The City and South London Railway (C&SLR) was the first successful deep-level underground "tube" railway in the world, and the first major railway to use electric traction. The railway was originally intended for cable-hauled trains, but owing ...
was the first electric-traction rapid transit railway, which was also fully underground.Ovenden, 2007: 7 Prior to opening, the line was to be called the "City and South London Subway", thus introducing the term Subway into railway terminology. Both railways, alongside others, were eventually merged into London Underground. The 1893 Liverpool Overhead Railway was designed to use electric traction from the outset. The technology quickly spread to other cities in Europe, the United States, Argentina, and Canada, with some railways being converted from steam and others being designed to be electric from the outset. Budapest, Chicago, Glasgow and New York City all converted or purpose-designed and built electric rail services. Advancements in technology have allowed new automated services. Hybrid solutions have also evolved, such as tram-train and premetro, which incorporate some of the features of rapid transit systems. In response to cost, engineering considerations and topological challenges some cities have opted to construct tram systems, particularly those in Australia, where density in cities was low and
suburb A suburb (more broadly suburban area) is an area within a metropolitan area, which may include commercial and mixed-use, that is primarily a residential area. A suburb can exist either as part of a larger city/urban area or as a separate ...
s tended to spread out. Since the 1970s, the viability of underground train systems in Australian cities, particularly
Sydney Sydney ( ) is the capital city of the state of New South Wales, and the most populous city in both Australia and Oceania. Located on Australia's east coast, the metropolis surrounds Sydney Harbour and extends about towards the Blue Mountain ...
and Melbourne, has been reconsidered and proposed as a solution to over-capacity. Melbourne had tunnels and stations developed in the 1970s and opened in 1980. The first line of
Sydney Metro The Sydney Metro is a fully automated rapid transit system serving the city of Sydney, New South Wales, Australia. Currently consisting of one line that opened on 26 May 2019, it runs from Tallawong to Chatswood and consists of 13 stations ...
, was opened in 2019. Since the 1960s, many new systems were introduced in Europe, Asia and Latin America. In the 21st century, most new expansions and systems are located in Asia, with China becoming the world's leader in metro expansion, operating some of the largest and busiest systems while possessing almost 60 cities that are operating, constructing or planning a rapid transit system.


Operation

Rapid transit is used in cities,
agglomerations An urban area, built-up area or urban agglomeration is a human settlement with a high population density and infrastructure of built environment. Urban areas are created through urbanization and are categorized by urban morphology as cities, ...
, and
metropolitan area A metropolitan area or metro is a region that consists of a densely populated urban agglomeration and its surrounding territories sharing industries, commercial areas, transport network, infrastructures and housing. A metro area usually com ...
s to transport large numbers of people often short distances at high frequency. The extent of the rapid transit system varies greatly between cities, with several transport strategies. Some systems may extend only to the limits of the inner city, or to its inner ring of
suburb A suburb (more broadly suburban area) is an area within a metropolitan area, which may include commercial and mixed-use, that is primarily a residential area. A suburb can exist either as part of a larger city/urban area or as a separate ...
s with trains making frequent station stops. The outer suburbs may then be reached by a separate commuter rail network where more widely spaced stations allow higher speeds. In some cases the differences between urban rapid transit and suburban systems are not clear. Rapid transit systems may be supplemented by other systems such as trolleybuses, regular
bus A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle that carries significantly more passengers than an average car or van. It is most commonly used in public transport, but is also in use for cha ...
es, trams, or commuter rail. This combination of transit modes serves to offset certain limitations of rapid transit such as limited stops and long walking distances between outside access points. Bus or tram feeder systems transport people to rapid transit stops.


Lines

Each rapid transit system consists of one or more ''lines'', or circuits. Each line is serviced by at least one specific route with trains stopping at all or some of the line's stations. Most systems operate several routes, and distinguish them by colors, names, numbering, or a combination thereof. Some lines may share track with each other for a portion of their route or operate solely on their own right-of-way. Often a line running through the city center forks into two or more branches in the suburbs, allowing a higher service frequency in the center. This arrangement is used by many systems, such as the Copenhagen Metro, the Milan Metro, the Oslo Metro and the
New York City Subway The New York City Subway is a rapid transit system owned by the government of New York City and leased to the New York City Transit Authority, an affiliate agency of the state-run Metropolitan Transportation Authority (MTA). Opened on October 2 ...
. Alternatively, there may be a single central terminal (often shared with the central railway station), or multiple interchange stations between lines in the city center, for instance in the Prague Metro. The London Underground and Paris Métro are densely built systems with a matrix of crisscrossing lines throughout the cities. The
Chicago 'L' (''City in a Garden''); I Will , image_map = , map_caption = Interactive Map of Chicago , coordinates = , coordinates_footnotes = , subdivision_type = Country , subdivision_name ...
has most of its lines converging on The Loop, the main business, financial, and cultural area. Some systems have a circular line around the city center connecting to radially arranged outward lines, such as the Moscow Metro's Koltsevaya Line and Beijing Subway's Line 10. The capacity of a line is obtained by multiplying the car capacity, the train length, and the service frequency. Heavy rapid transit trains might have six to twelve cars, while lighter systems may use four or fewer. Cars have a capacity of 100 to 150 passengers, varying with the
seated to standing ratio In urban public transport, provision is made for standing passengers, often called straphangers or standees, to rationalize operation and to provide extra capacity during rush hour. Occurrence On crowded rapid transit urban lines, while most tr ...
—more standing gives higher capacity. The minimum time interval between trains is shorter for rapid transit than for mainline railways owing to the use of
Communications based train control Communications-based train control (CBTC) is a railway signaling system that uses telecommunications between the train and track equipment for traffic management and infrastructure control. CBTC allows a train's position to be known more accurat ...
: the minimum headway can reach 90 seconds, but many systems typically use 120 seconds to allow for recovery from delays. Typical capacity lines allow 1,200 people per train, giving 36,000
passengers per hour per direction Passengers per hour per direction (p/h/d), passengers per hour in peak direction (pphpd) or corridor capacity is a measure of the route capacity of a rapid transit or public transport system. Definition The corridor capacity in the passenger t ...
. However, much higher capacities are attained in East Asia with ranges of 75,000 to 85,000 people per hour achieved by MTR Corporation's urban lines in Hong Kong.


Network topologies

Rapid transit topologies are determined by a large number of factors, including geographical barriers, existing or expected travel patterns, construction costs, politics, and historical constraints. A transit system is expected to serve an ''area'' of land with a set of ''lines'', which consist of shapes summarized as "I", "L", "U", "S", and "O" shapes or loops. Geographical barriers may cause chokepoints where transit lines must converge (for example, to cross a body of water), which are potential congestion sites but also offer an opportunity for transfers between lines. Ring lines provide good coverage, connect between the radial lines and serve tangential trips that would otherwise need to cross the typically congested core of the network. A rough grid pattern can offer a wide variety of routes while still maintaining reasonable speed and frequency of service. A study of the 15 world largest subway systems suggested a universal shape composed of a dense core with branches radiating from it.


Passenger information

Rapid transit operators have often built up strong brands, often focused on easy recognition—to allow quick identification even in the vast array of signage found in large cities—combined with the desire to communicate speed, safety, and authority. In many cities, there is a single corporate image for the entire transit authority, but the rapid transit uses its own logo that fits into the profile. A
transit map A transit map is a topological map in the form of a schematic diagram used to illustrate the routes and stations within a public transport system—whether this be bus, tram, rapid transit, commuter rail or ferry routes. The main components are ...
is a topological map or schematic
diagram A diagram is a symbolic representation of information using visualization techniques. Diagrams have been used since prehistoric times on walls of caves, but became more prevalent during the Enlightenment. Sometimes, the technique uses a three- ...
used to show the routes and stations in a public transport system. The main components are color-coded lines to indicate each line or service, with named icons to indicate stations. Maps may show only rapid transit or also include other modes of public transport.Ovenden, 2007: 9 Transit maps can be found in transit vehicles, on platforms, elsewhere in stations, and in printed
timetables A schedule or a timetable, as a basic time-management tool, consists of a list of times at which possible tasks, events, or actions are intended to take place, or of a sequence of events in the chronological order in which such things are i ...
. Maps help users understand the interconnections between different parts of the system; for example, they show the interchange stations where passengers can transfer between lines. Unlike conventional maps, transit maps are usually not geographically accurate, but emphasize the topological connections among the different stations. The graphic presentation may use straight lines and fixed angles, and often a fixed minimum distance between stations, to simplify the display of the transit network. Often this has the effect of compressing the distance between stations in the outer area of the system, and expanding distances between those close to the center. Some systems assign unique alphanumeric codes to each of their stations to help commuters identify them, which briefly encodes information about the line it is on, and its position on the line.Ström, 1998: 58 For example, on the Singapore MRT, Changi Airport MRT station has the alphanumeric code CG2, indicating its position as the 2nd station on the Changi Airport branch of the East West Line. Interchange stations would have at least two codes, for example, Raffles Place MRT station has two codes, NS26 and EW14, the 26th station on the North South Line and the 14th station on the East West Line. Seoul Metro is another example that utilizes a code for its stations. But unlike that of Singapore's MRT, it is mostly numbers. Based on the line number, for example Sinyongsan station, coded as station 429. As it is on Line 4, the first number of the station code is 4. The last 2 numbers will be the station number on that line. Interchange stations can have multiple codes. Like City Hall station in Seoul which is served by Line 1 and Line 2. It has a code of 132 and 201 respectively. The Line 2 is a circle line and the first stop is City Hall, therefore, City Hall has the station code of 201. For lines without a number like Bundang line it will have an alphanumeric code. Lines without a number that are operated by KORAIL will start with the letter 'K'. With widespread use of the Internet and
cell phone A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link whil ...
s globally, transit operators now use these technologies to present information to their users. In addition to online maps and timetables, some transit operators now offer real-time information which allows passengers to know when the next vehicle will arrive, and expected travel times. The standardized
GTFS GTFS, which stands for General Transit Feed Specification or (originally) Google Transit Feed Specification, defines a common format for public transportation schedules and associated geographic information. GTFS contains only static or schedul ...
data format for transit information allows many third-party software developers to produce web and smartphone app programs which give passengers customized updates regarding specific transit lines and stations of interest.


Safety and security

Compared to other modes of transport, rapid transit has a good safety record, with few accidents. Rail transport is subject to strict safety regulations, with requirements for procedure and maintenance to minimize risk. Head-on collisions are rare due to use of double track, and low operating speeds reduce the occurrence and severity of rear-end collisions and derailments. Fire is more of a danger underground, such as the King's Cross fire in London in November 1987, which killed 31 people. Systems are generally built to allow evacuation of trains at many places throughout the system. High platforms (usually over 1 meter / 3 feet) are a safety risk, as people falling onto the tracks have trouble climbing back.
Platform screen doors Platform screen doors (PSDs), also known as platform edge doors (PEDs), are used at some train, rapid transit and people mover stations to separate the platform from train tracks, as well as on some bus rapid transit, tram and light rail syste ...
are used on some systems to eliminate this danger. Rapid transit facilities are public spaces and may suffer from
security Security is protection from, or resilience against, potential harm (or other unwanted coercive change) caused by others, by restraining the freedom of others to act. Beneficiaries (technically referents) of security may be of persons and social ...
problems: petty crimes, such as
pickpocketing Pickpocketing is a form of larceny that involves the stealing of money or other valuables from the person or a victim's pocket without them noticing the theft at the time. It may involve considerable dexterity and a knack for Misdirection (magic ...
and baggage theft, and more serious violent crimes, as well as sexual assaults on tightly packed trains and platforms. Security measures include video surveillance,
security guard A security guard (also known as a security inspector, security officer, or protective agent) is a person employed by a government or private party to protect the employing party's assets (property, people, equipment, money, etc.) from a variety ...
s, and conductors. In some countries a specialized transit police may be established. These security measures are normally integrated with measures to protect revenue by checking that passengers are not travelling without paying. Some subway systems, such as the Beijing Subway, which is ranked by Worldwide Rapid Transit Data as the "World's Safest Rapid Transit Network" in 2015, incorporate airport-style security checkpoints at every station. Rapid transit systems have been subject to terrorism with many casualties, such as the 1995
Tokyo subway sarin gas attack The was an act of domestic terrorism perpetrated on 20 March 1995, in Tokyo, Japan, by members of the cult movement Aum Shinrikyo. In five coordinated attacks, the perpetrators released sarin on three lines of the Tokyo Metro (then ''Teito Rapid ...
and the 2005 " 7/7" terrorist bombings on the London Underground.


Added features

Some rapid transport trains have extra features such as wall sockets, cellular reception (typically using leaky feeder in tunnels and DAS antennas in stations), as well as Wi-Fi connectivity. The first metro system in the world to enable full mobile phone reception in underground stations and tunnels was Singapore's Mass Rapid Transit (MRT) system which launched its first underground mobile phone network (using AMPS) in 1989. Nowadays, many metro systems, such as the Hong Kong Mass Transit Railway (MTR) and the Berlin U-Bahn, provide mobile data connections in their tunnels for various network operators.


Infrastructure

The technology used for public, mass rapid transit has undergone significant changes in the years since the
Metropolitan Railway The Metropolitan Railway (also known as the Met) was a passenger and goods railway that served London from 1863 to 1933, its main line heading north-west from the capital's financial heart in the City to what were to become the Middlesex su ...
opened publicly in London in 1863. High capacity Monorails with larger and longer trains can be classified as rapid transit systems. Such monorail systems recently started operating in
Chongqing Chongqing ( or ; ; Sichuanese dialects, Sichuanese pronunciation: , Standard Mandarin pronunciation: ), Postal Romanization, alternately romanized as Chungking (), is a Direct-administered municipalities of China, municipality in Southwes ...
and São Paulo. Light metro is a subclass of rapid transit that has the speed and grade separation of a "full metro" but is designed for smaller passenger numbers. It often has smaller loading gauges, lighter train cars and smaller consists of typically two to four cars. Light metros are typically used as feeder lines into the main rapid transit system. For instance, the
Wenhu Line The Wenhu or Brown line (code BR) is a metro line in Taipei operated by Taipei Metro, named after the districts it connects: Wenshan and Neihu. It is an automated medium-capacity rubber-tyred metro line and is long, serving a total of 24 st ...
of the Taipei Metro serves many relatively sparse neighbourhoods and feeds into and complements the high capacity metro lines. Some systems have been built from scratch, others are reclaimed from former commuter rail or suburban tramway systems that have been upgraded, and often supplemented with an underground or elevated downtown section. At grade alignments with a dedicated right-of-way are typically used only outside dense areas, since they create a physical barrier in the urban fabric that hinders the flow of people and vehicles across their path and have a larger physical footprint. This method of construction is the cheapest as long as land values are low. It is often used for new systems in areas that are planned to fill up with buildings after the line is built.


Trains

Most rapid transit trains are electric multiple units with lengths from three to over ten cars.White, 2002: 64 Crew sizes have decreased throughout history, with some modern systems now running completely unstaffed trains. Other trains continue to have drivers, even if their only role in normal operation is to open and close the doors of the trains at stations. Power is commonly delivered by a third rail or by overhead wires. The whole London Underground network uses fourth rail and others use the
linear motor A linear motor is an electric motor that has had its stator and rotor "unrolled", thus, instead of producing a torque (rotation), it produces a linear force along its length. However, linear motors are not necessarily straight. Characteristicall ...
for propulsion. Some urban rail lines are built to a
loading gauge A loading gauge is a diagram or physical structure that defines the maximum height and width dimensions in railway vehicles and their loads. Their purpose is to ensure that rail vehicles can pass safely through tunnels and under bridges, and ke ...
as large as that of main-line railways; others are built to a smaller one and have tunnels that restrict the size and sometimes the shape of the train compartments. One example is most of the London Underground, which has acquired the informal term "tube train" due to the cylindrical shape of the trains used on the deep tube lines. 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 A loading gauge is a diagram or physical structure that defines the maximum height and width dimensions in railway vehicles and their loads. Their purpose is to ensure that rail vehicles can pass safely through tunnels and under bridges, and ke ...
from one sub network may be transported along other lines that use larger trains. On some networks such operations are part of normal services.


Tracks

Most rapid transit systems use conventional
standard gauge A standard-gauge railway is a railway with a track gauge of . The standard gauge is also called Stephenson gauge (after George Stephenson), International gauge, UIC gauge, uniform gauge, normal gauge and European gauge in Europe, and SGR in Ea ...
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 Mexico City Metro, 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 tire A flat tire (British English: flat tyre) is a deflated pneumatic tyre, which can cause the rim of the wheel to ride on the tire tread or the ground potentially resulting in loss of control of the vehicle or irreparable damage to the tire. The mos ...
s 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 Rennes (; br, Roazhon ; Gallo: ''Resnn''; ) is a city in the east of Brittany in northwestern France at the confluence of the Ille and the Vilaine. Rennes is the prefecture of the region of Brittany, as well as the Ille-et-Vilaine department ...
, 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. However, they have higher maintenance costs and are less energy efficient. They also lose traction when weather conditions are wet or icy, preventing above-ground use of the Montréal Metro and limiting it on the Sapporo Municipal Subway, but not rubber-tired systems in other cities. Some cities with steep hills incorporate
mountain railway A mountain railway is a railway that operates in a mountainous region. It may operate through the mountains by following mountain valleys and tunneling beneath mountain passes, or it may climb a mountain to provide transport to and from the sum ...
technologies in their metros. One of the lines of the
Lyon Metro The Lyon Metro (french: Métro de Lyon) is a rapid transit system serving Lyon Metropolis, France. First opened in 1974, it currently consists of four lines, serving 40 stations and comprising of route. Part of the Transports en Commun Lyonnais ...
includes a section of rack (cog) railway, while the
Carmelit The Carmelit ( he, כַּרְמְלִית Arabic: كرمليت) is an underground funicular, funicular railway in Haifa, Israel. Construction started in 1956 and ended in 1959. It is the oldest underground transit system in the Middle East and c ...
, 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 The Chongqing Rail Transit (branded as CRT; also known as Chongqing Metro) is the rapid transit system in the city of Chongqing, China. In operation since 2005, it serves the transportation needs of the city's main business and entertainment ...
's monorail lines which are widely used in a rapid transit setting.


Motive power

Although trains on very early rapid transit systems like the
Metropolitan Railway The Metropolitan Railway (also known as the Met) was a passenger and goods railway that served London from 1863 to 1933, its main line heading north-west from the capital's financial heart in the City to what were to become the Middlesex su ...
were powered using
steam engine A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be trans ...
s, either via cable haulage or
steam locomotive A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material (usually coal, oil or, rarely, wood) to heat water in the locomot ...
s, nowadays virtually all metro trains use
electric power Electric power is the rate at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. Standard prefixes apply to watts as with other SI units: thousands, millions and billions o ...
and are built to run as
multiple unit A multiple-unit train or simply multiple unit (MU) is a self-propelled train composed of one or more carriages joined together, which when coupled to another multiple unit can be controlled by a single driver, with multiple-unit train contr ...
s. Power for the trains, referred to as traction power, is usually supplied via 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 The Shanghai Metro (; Shanghainese: ''Zaon6he5 Di6thiq7'') is a rapid transit system in Shanghai, operating urban and suburban transit services to 14 of its 16 municipal districts and to Kunshan, Jiangsu Province. Served as a part of Shangha ...
, overhead wires are employed on some systems that are predominantly underground, as in Barcelona, Fukuoka, Hong Kong, Madrid, and
Shijiazhuang Shijiazhuang (; ; Mandarin: ), formerly known as Shimen and romanized as Shihkiachwang, is the capital and most populous city of China’s North China's Hebei Province. Administratively a prefecture-level city, it is about southwest of Beijin ...
. 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.


Tunnels

Underground tunnels move traffic away from street level, avoiding delays caused by
traffic congestion Traffic congestion is a condition in transport that is characterized by slower speeds, longer trip times, and increased vehicular queueing. Traffic congestion on urban road networks has increased substantially since the 1950s. When traffic de ...
and leaving more land available for buildings and other uses. In areas of high land prices and dense land use, tunnels may be the only economic route for mass transportation. Cut-and-cover tunnels are constructed by digging up city streets, which are then rebuilt over the tunnel; alternatively, tunnel-boring machines can be used to dig deep-bore tunnels that lie further down in
bedrock In geology, bedrock is solid Rock (geology), rock that lies under loose material (regolith) within the crust (geology), crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface mater ...
. The construction of an underground metro is an expensive
project A project is any undertaking, carried out individually or collaboratively and possibly involving research or design, that is carefully planned to achieve a particular goal. An alternative view sees a project managerially as a sequence of even ...
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
street A street is a public thoroughfare in a built environment. It is a public parcel of land adjoining buildings in an urban context, on which people may freely assemble, interact, and move about. A street can be as simple as a level patch of dirt, ...
s 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 Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...
; in the oldest systems,
brick A brick is a type of block used to build walls, pavements and other elements in masonry construction. Properly, the term ''brick'' denotes a block composed of dried clay, but is now also used informally to denote other chemically cured cons ...
, 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 A tunnelling shield is a protective structure used during the excavation of large, man-made tunnels. When excavating through ground that is soft, liquid, or otherwise unstable, there is a potential Occupational safety and health, health and safet ...
, thus avoiding almost any disturbance to existing streets, buildings, and utilities. But problems with ground water are more likely, and tunneling through native
bedrock In geology, bedrock is solid Rock (geology), rock that lies under loose material (regolith) within the crust (geology), crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface mater ...
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 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 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: * Deepest stations in Saint Petersburg Metro, Russia: ** '' Admiralteyskaya'' (''The Admiralty'', , opened 2011, probably the best candidate) ** ''
Komendantsky Prospekt Komendantsky Prospekt (russian: Комендантский проспект), literally translate - Avenue of Commendants ) is a station on the Frunzensko-Primorskaya Line of the Saint Petersburg Metro, opened on April 2, 2005. Its main decoration ...
'' (''The Commandant Avenue'', , opened 2005) ** '' Chernyshevskaya'' ('' Chernyshevsky'', , opened 1958) ** '' Ploshad Lenina'' ('' Lenin Square'', , opened 1958) * ''
Arsenalna Arsenalna ( uk, Арсена́льна, translit=Arsenál’na, , ) is a station on Kyiv Metro’s Sviatoshynsko-Brovarska Line. The station was opened along with the first stage and is currently the deepest station in the world at . This is ...
'' station in Kyiv Metro, Ukraine (, opened 1960, built under a hill) *''
Hongtudi station Hongtudi is an interchange station on Line 6 and Line 10 of Chongqing Rail Transit in Chongqing Municipality, China. It is located in the Jiangbei District. The lowest level being 94 meters below ground makes it one of the world's deepest ...
'' in
Chongqing Metro The Chongqing Rail Transit (branded as CRT; also known as Chongqing Metro) is the rapid transit system in the city of Chongqing, China. In operation since 2005, it serves the transportation needs of the city's main business and entertainment d ...
, China (, opened in 2016) *''Liyuchi station'' in
Chongqing Metro The Chongqing Rail Transit (branded as CRT; also known as Chongqing Metro) is the rapid transit system in the city of Chongqing, China. In operation since 2005, it serves the transportation needs of the city's main business and entertainment d ...
, China (, opened in 2017) * '' Park Pobedy'' station in Moscow (~, opened 2005, built under a hill) * ''Puhung'' station in Pyongyang Metro, North Korea (which doubles as a
nuclear shelter A bomb shelter is a structure designed to provide protection against the effects of a bomb. Types of shelter Different kinds of bomb shelters are configured to protect against different kinds of attack and strengths of hostile explosives. Air ...
) * '' Washington Park'' MAX Light Rail station in Portland, Oregon (built under a hill), 260 feet (80 m) 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 The University of Hong Kong (HKU) (Chinese: 香港大學) is a public research university in Hong Kong. Founded in 1887 as the Hong Kong College of Medicine for Chinese, it is the oldest tertiary institution in Hong Kong. HKU was also the fir ...
) situated over below ground level, to serve passengers on the
Mid-levels Mid-Levels is an affluent residential area on Hong Kong Island in Hong Kong. It is located between Victoria Peak and Central. Residents are predominantly more affluent Hong Kong locals and expatriate professionals. The Mid-Levels is further ...
. They have several entrances/exits equipped with high-speed lifts, instead of
escalators An escalator is a moving staircase which carries people between floors of a building or structure. It consists of a motor-driven chain of individually linked steps on a track which cycle on a pair of tracks which keep the step tread horizo ...
. These kinds of exits have existed in many London Underground stations and stations in former Soviet Union nations.


Elevated railways

Elevated railways are a cheaper and easier way to build an exclusive right-of-way without digging expensive tunnels or creating barriers. In addition to street level railways they may also be the only other feasible alternative due to considerations such as a high water table close to the city surface that raises the cost of, or even precludes underground railways (e.g. Miami). Elevated guideways were popular around the beginning of the 20th century, but fell out of favor; they came back into fashion in the last quarter of the century—often in combination with driverless systems, for instance Vancouver's SkyTrain, London's Docklands Light Railway, the
Miami Metrorail Metrorail is the heavy rail rapid transit system of Miami and Miami-Dade County in the U.S. state of Florida. Metrorail is operated by Miami-Dade Transit (MDT), a departmental agency of Miami-Dade County. Opened in 1984, it is Florida's only ra ...
, and the Bangkok Skytrain.


Stations

Stations function as hubs to allow passengers to board and disembark from trains. They are also payment checkpoints and allow passengers to transfer between modes of transport, for instance to buses or other trains. Access is provided via either island- or side platforms. Underground stations, especially deep-level ones, increase the overall transport time: long escalator rides to the platforms mean that the stations can become bottlenecks if not adequately built. Some underground and elevated stations are integrated into vast
underground Underground most commonly refers to: * Subterranea (geography), the regions beneath the surface of the Earth Underground may also refer to: Places * The Underground (Boston), a music club in the Allston neighborhood of Boston * The Underground (S ...
or skyway networks respectively, that connect to nearby commercial buildings. In suburbs, there may be a " park and ride" connected to the station. To allow easy access to the trains, the
platform height Railway platform height is the built height – ''above top of rail (ATR)'' – of passenger platforms at stations. A connected term is ''train floor height'', which refers to the ATR height of the floor of rail vehicles. Worldwide, there are ...
allows step-free access between platform and train. If the station complies with
accessibility Accessibility is the design of products, devices, services, vehicles, or environments so as to be usable by people with disabilities. The concept of accessible design and practice of accessible development ensures both "direct access" (i. ...
standards, it allows both disabled people and those with wheeled baggage easy access to the trains, though if the track is curved there can be a gap between the train and platform. Some stations use
platform screen doors Platform screen doors (PSDs), also known as platform edge doors (PEDs), are used at some train, rapid transit and people mover stations to separate the platform from train tracks, as well as on some bus rapid transit, tram and light rail syste ...
to increase safety by preventing people falling onto the tracks, as well as reducing ventilation costs. The deepest station in the world is Arsenalna station in Kyiv, Ukraine (105.5 m). Particularly in the former Soviet Union and other Eastern European countries, but to an increasing extent elsewhere, the stations were built with splendid decorations such as marble walls, polished granite floors and mosaics—thus exposing the public to art in their everyday life, outside galleries and museums. The systems in Moscow, St. Petersburg, Tashkent and Kyiv are widely regarded as some of the most beautiful in the world. Several other cities such as London,
Stockholm Stockholm () is the Capital city, capital and List of urban areas in Sweden by population, largest city of Sweden as well as the List of urban areas in the Nordic countries, largest urban area in Scandinavia. Approximately 980,000 people liv ...
, Montreal,
Lisbon Lisbon (; pt, Lisboa ) is the capital and largest city of Portugal, with an estimated population of 544,851 within its administrative limits in an area of 100.05 km2. Grande Lisboa, Lisbon's urban area extends beyond the city's administr ...
, Naples and Los Angeles have also focused on art, which may range from decorative wall claddings, to large, flamboyant artistic schemes integrated with station architecture, to displays of ancient artifacts recovered during station construction. It may be possible to profit by attracting more passengers by spending relatively small amounts on grand architecture, art, cleanliness,
accessibility Accessibility is the design of products, devices, services, vehicles, or environments so as to be usable by people with disabilities. The concept of accessible design and practice of accessible development ensures both "direct access" (i. ...
, lighting and a feeling of safety.


Crew size and automation

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 Conductor or conduction may refer to: Music * Conductor (music), a person who leads a musical ensemble, such as an orchestra. * ''Conductor'' (album), an album by indie rock band The Comas * Conduction, a type of structured free improvisation ...
" 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 Closed-circuit television (CCTV), also known as video surveillance, is the use of video cameras to transmit a signal to a specific place, on a limited set of monitors. It differs from broadcast television in that the signal is not openly t ...
monitors are often provided for that purpose. A replacement system for human drivers became available in the 1960s, with the advancement of
computer A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...
ized 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 San Francisco Bay Area's BART network. 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 Evacuation or Evacuate may refer to: * Casualty evacuation (CASEVAC), patient evacuation in combat situations * Casualty movement, the procedure for moving a casualty from its initial location to an ambulance * Emergency evacuation, removal of per ...
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 unstaffed 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 Val may refer to: Val-a Film * ''Val'' (film), an American documentary about Val Kilmer, directed by Leo Scott and Ting Poo Military equipment * Aichi D3A, a Japanese World War II dive bomber codenamed "Val" by the Allies * AS Val, a Sov ...
(''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 unstaffed 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 and the Kelana Jaya Line in Kuala Lumpur, both which carries no crew members. Systems that use automatic trains also commonly employ full-height
platform screen doors Platform screen doors (PSDs), also known as platform edge doors (PEDs), are used at some train, rapid transit and people mover stations to separate the platform from train tracks, as well as on some bus rapid transit, tram and light rail syste ...
or half-height
automatic platform gate Automatic may refer to: Music Bands * Automatic (band), Australian rock band * Automatic (American band), American rock band * The Automatic, a Welsh alternative rock band Albums * ''Automatic'' (Jack Bruce album), a 1983 electronic rock ...
s in order to improve safety and ensure passenger confidence, but this is not universal, as networks like Nuremberg do not, using
infrared sensors Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
instead to detect obstacles on the track. Conversely, some lines which retain drivers or manual train operation nevertheless use PSDs, 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 Line 1 or 1 line may refer to: Public transport Africa * Line 1 (Algiers Metro), Algeria * Cairo Metro Line 1, Egypt Asia China * Line 1 (Beijing Subway) * Line 1 (Changchun Rail Transit) * Line 1 (Changsha Metro) * Line 1 (Changzhou Metro) * L ...
was subsequently converted to unattended operation by 2012, and it is expected that Line 4 will follow by 2023. The
North East MRT line The North East MRT line (NEL) is a high-capacity Mass Rapid Transit (MRT) line in Singapore. Operated by SBS Transit, it is the shortest MRT line at . The line runs from HarbourFront station in southern Singapore to Punggol station in the n ...
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 South Island line.


Modal tradeoffs and interconnections

Since the 1980s, trams have incorporated several features of rapid transit: light rail systems (trams) run on their own
rights-of-way Right of way is the legal right, established by grant from a landowner or long usage (i.e. by prescription), to pass along a specific route through property belonging to another. A similar ''right of access'' also exists on land held by a gov ...
, thus avoiding congestion; they remain on the same level as buses and cars. Some light rail systems have elevated or underground sections. Both new and upgraded tram systems allow faster speed and higher capacity, and are a cheap alternative to construction of rapid transit, especially in smaller cities. A premetro design means that an underground rapid transit system is built in the city center, but only a light rail or tram system in the suburbs. Conversely, other cities have opted to build a full metro in the suburbs, but run trams in city streets to save the cost of expensive tunnels. In North America, interurbans were constructed as
street-running A street running train is a train which runs on a track built on public streets. The rails are embedded in the roadway, and the train shares the street with other users, such as pedestrians, cars and cyclists, thus often being referred to as ru ...
suburban trams, without the grade-separation of rapid transit. Premetros also allow a gradual upgrade of existing tramways to rapid transit, thus spreading the investment costs over time. They are most common in Germany with the name Stadtbahn. Suburban commuter rail is a heavy rail system that operates at a lower frequency than urban rapid transit, with higher average speeds, often only serving one station in each village and town. Commuter rail systems of some cities (such as German S-Bahns, Jakarta's KRL Commuterline, Chennai Suburban, Australian suburban networks, Danish S-tog etc.) can be seen as the substitute for the city's rapid transit system providing frequent mass transit within city. In contrast, the mainly urban rapid transit systems in some cities (such as the Dubai Metro,
Shanghai Metro The Shanghai Metro (; Shanghainese: ''Zaon6he5 Di6thiq7'') is a rapid transit system in Shanghai, operating urban and suburban transit services to 14 of its 16 municipal districts and to Kunshan, Jiangsu Province. Served as a part of Shangha ...
, MetroSur of the
Madrid Metro The Madrid Metro (Spanish: ''Metro de Madrid'') is a rapid transit system serving the city of Madrid, capital of Spain. The system is the 14th longest rapid transit system in the world, with a total length of 293 km (182 mi). Its gro ...
, Taipei Metro, Kuala Lumpur Rapid Transit etc.) have lines that fan out to reach the outer suburbs. With some other urban or "near urban" rapid transit systems ( Guangfo Metro,
Bay Area Rapid Transit Bay Area Rapid Transit (BART) is a rapid transit system serving the San Francisco Bay Area in California. BART serves 50 stations along six routes on of rapid transit lines, including a spur line in eastern Contra Costa County which uses ...
,
Los Teques Metro The Los Teques Metro is a suburban mass-transit system in the city of Los Teques, Venezuela with connections to important surrounding cities and communities. It was opened to public service on November 3, 2006. The Los Teques Metro currently oper ...
and Seoul Subway Line 7, etc.) serving bi- and multi-nucleus
agglomerations An urban area, built-up area or urban agglomeration is a human settlement with a high population density and infrastructure of built environment. Urban areas are created through urbanization and are categorized by urban morphology as cities, ...
. Some cities have opted for two tiers of urban railways: an urban rapid transit system (such as the Paris Métro, Berlin U-Bahn, London Underground,
Sydney Metro The Sydney Metro is a fully automated rapid transit system serving the city of Sydney, New South Wales, Australia. Currently consisting of one line that opened on 26 May 2019, it runs from Tallawong to Chatswood and consists of 13 stations ...
, Tokyo subway, Jakarta MRT and Philadelphia Subway) and a suburban system (such as their counterparts RER, S-Bahn, future Crossrail & London Overground, Sydney Trains, JR Urban Lines, KRL Commuterline and
Regional Rail Regional rail, also known as local trains and stopping trains, are passenger rail services that operate between towns and cities. These trains operate with more stops over shorter distances than inter-city rail, but fewer stops and faster serv ...
respectively). Such systems are known variously as S-trains, suburban service, or (sometimes) regional rail. The suburban systems may have their own purpose built trackage, run at similar "rapid transit-like" frequencies, and (in many countries) are operated by the national railway company. In some cities these suburban services run through tunnels in the city center and have direct transfers to the rapid transit system, on the same or adjoining platforms.White, 2002: 63–64 In some cases, such as the London Underground and the London Overground, suburban and rapid transit systems even run on the exact same track along some sections. California's BART, Federal District's Metrô-DF and Washington's Metrorail system is an example of a hybrid of the two: in the suburbs the lines function like a commuter rail line, with longer intervals and longer distance between stations; in the downtown areas, the stations become closer together and many lines interline with intervals dropping to typical rapid transit headways.


Costs, benefits, and impacts

, 212 cities have built rapid transit systems. The capital cost is high, as is the risk of cost overrun and benefit shortfall;
public financing Public finance is the study of the role of the government in the economy. It is the branch of economics that assesses the government revenue and government expenditure of the public authorities and the adjustment of one or the other to achie ...
is normally required. Rapid transit is sometimes seen as an alternative to an extensive
road transport Road transport or road transportation is a type of transport using roads. Transport on roads can be roughly grouped into the transportation of goods and transportation of people. In many countries licensing requirements and safety regulations e ...
system with many motorways;Banister and Berechman, 2000: 258 the rapid transit system allows higher capacity with less land use, less environmental impact, and a lower cost. Elevated or underground systems in city centers allow the transport of people without occupying expensive land, and permit the city to develop compactly without physical barriers. Motorways often depress nearby residential land values, but proximity to a rapid transit station often triggers commercial and residential growth, with large transit oriented development office and housing blocks being constructed. Also, an efficient transit system can decrease the economic welfare loss caused by the increase of population density in a metropolis. Rapid transit systems have high fixed costs. Most systems are publicly owned, by either local governments, transit authorities or national governments. Capital investments are often partially or completely financed by taxation, rather than by passenger fares, but must often compete with funding for roads. The transit systems may be operated by the owner or by a private company through a public service obligation. The owners of the systems often also own the connecting bus or rail systems, or are members of the local transport association, allowing for free transfers between modes. Almost all transit systems operate at a deficit, requiring fare revenue, advertising and subsidies to cover costs. The farebox recovery ratio, a ratio of ticket income to operating costs, is often used to assess operational profitability, with some systems including Hong Kong's MTR Corporation, and Taipei achieving recovery ratios of well over 100%. This ignores both heavy capital costs incurred in building the system, which are often subsidized with soft loans and whose servicing is excluded from calculations of profitability, as well as ancillary revenue such as income from real estate portfolios. Some systems, particularly Hong Kong's, extensions are partly financed by the sale of land whose value has appreciated by the new access the extension has brought to the area,Kjenstad, 1994: 46 a process known as value capture. Urban land-use planning policies are essential for the success of rapid transit systems, particularly as mass transit is not feasible in low-density communities. Transportation planners estimate that to support rapid rail services, there must be a residential housing density of twelve dwelling units per acre.


See also

*
List of metro systems This list of metro systems includes electrified rapid transit train systems worldwide. In some parts of the world, metro systems are referred to as subways, U-Bahn or undergrounds. , 205 cities in 61 countries have a metro system. The London ...
*
Bus rapid transit Bus rapid transit (BRT), also called a busway or transitway, is a bus-based public transport system designed to have much more capacity, reliability and other quality features than a conventional bus system. Typically, a BRT system includes ...
* Megaproject *
Personal rapid transit Personal rapid transit (PRT), also referred to as podcars or guided/railed taxis, is a public transport mode featuring small low-capacity automated vehicles operating on a network of specially built guideways. PRT is a type of automated guideway ...
*
Rapid transit track gauge The vast majority of rapid transit systems use . Some of the largest and oldest subway systems in the world use standard gauge in agreement with the country wide dominant usage for track gauge, e.g. London Underground (1863), Chicago "L" (1892), ...


References


Citations


Sources

* * Bobrick, Benson (1981). ''Labyrinths of Iron'': ''a'' 'n''''History of the World's Subways''. New York: Newsweek Books. . * * * * * * * * * *


External links


UrbanRail
; Databases
metro data
Database of metro systems around the world {{Authority control Passenger rail transport Articles containing video clips 1863 introductions