Urban rail transit is an all-encompassing term for various types of local

rail Rail or rails may refer to: Rail transport *Rail transport and related matters *Rail (rail transport) or railway lines, the running surface of a railway Arts and media Film * ''Rails'' (film), a 1929 Italian film by Mario Camerini * ''Rail'' ( ...

systems providing passenger service within and around urban or

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 separ ...

an areas. The set of urban rail systems can be roughly subdivided into the following categories, which sometimes overlap because some systems or lines have aspects of multiple types.

Types

Tram

A ''tram'', ''streetcar'', or ''trolley'' system is a rail-based transit system that runs mainly or completely along streets (with

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 ...

), with a relatively-low capacity and frequent stops. Passengers usually board at the street or curb level, but

low-floor 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. ...

trams may allow level boarding. Longer-distance lines are called ''

interurban The Interurban (or radial railway in Europe and Canada) is a type of electric railway, with streetcar-like electric self-propelled rail cars which run within and between cities or towns. They were very prevalent in North America between 1900 ...

s'' or ''radial railways''. Few interurbans remain, most having been upgraded to commuter rail or light rail or abandoned. The term "tram" is used in most parts of the world. In North America, such systems are referred to as "streetcar" or "trolley" systems. In Germany, such systems are called "Straßenbahn", which literally translates as "street train" or "street railway". Updated tram systems have higher passenger capacities than traditional streetcars.

Light rail

A light rail system is a rail-based transit system that has higher capacity and speed than a tram, usually by operating in an exclusive

right-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 ...

separated from automobile traffic, but it is not, unlike rapid transit, fully grade-separated from other traffic. Light rail also generally operates with multiple-units trains, rather than single tramcars. It emerged as an evolution of trams/streetcars. Light rail systems vary significantly in terms of speed and capacity and range from slightly-improved tram systems to systems that are essentially rapid transit but with some level crossings. The term "light rail" is the most common term, but German systems are called "

Stadtbahn ' (; German for "city railway"; plural ') is a German word referring to various types of urban rail transport. One type of transport originated in the 19th century, firstly in Berlin and followed by Vienna, where rail routes were created that co ...

", which translates to "city railway". Chennai Metro Rail at Koyambedu

Rapid transit

rapid transit 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 ...

system is a

railway Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a p ...

, usually in an

urban area 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 ...

, with high passenger capacities and frequency of service and (usually) full

grade separation 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 tr ...

from other traffic, including other rail traffic. It is often known as "heavy rail" to distinguish it from light rail and from

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 ...

. In most parts of the world, such systems are known as a "metro", short for "metropolitan", which is itself short for "

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 ...

", the first such system in the world. The term "subway" is used in many American systems, as well as in

Glasgow Glasgow ( ; sco, Glesca or ; gd, Glaschu ) is the most populous city in Scotland and the fourth-most populous city in the United Kingdom, as well as being the 27th largest city by population in Europe. In 2020, it had an estimated popu ...

and in

Toronto Toronto ( ; or ) is the capital city of the Canadian province of Ontario. With a recorded population of 2,794,356 in 2021, it is the most populous city in Canada and the fourth most populous city in North America. The city is the anch ...

. The system in London is named the "Underground" and is commonly nicknamed the "tube". Systems in Germany are called "U-Bahn", which stands for ''Untergrundbahn'' ("underground rail"). Many systems in East, Southeast and South Asia like

Taipei Taipei (), officially Taipei City, is the capital and a special municipality of the Republic of China (Taiwan). Located in Northern Taiwan, Taipei City is an enclave of the municipality of New Taipei City that sits about southwest of the ...

Chennai Chennai (, ), formerly known as Madras ( the official name until 1996), is the capital city of Tamil Nadu, the southernmost Indian state. The largest city of the state in area and population, Chennai is located on the Coromandel Coast of th ...

and

Singapore Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, bor ...

, are called "MRT", which stands for "mass rapid transit". Systems that are predominantly elevated may be referred to as "L", as in

Chicago (''City in a Garden''); I Will , image_map = , map_caption = Interactive Map of Chicago , coordinates = , coordinates_footnotes = , subdivision_type = List of sovereign states, Count ...

, or "Skytrain", as in

Bangkok Bangkok, officially known in Thai as Krung Thep Maha Nakhon and colloquially as Krung Thep, is the capital and most populous city of Thailand. The city occupies in the Chao Phraya River delta in central Thailand and has an estimated populati ...

and

Vancouver Vancouver ( ) is a major city in western Canada, located in the Lower Mainland region of British Columbia. As the most populous city in the province, the 2021 Canadian census recorded 662,248 people in the city, up from 631,486 in 2016. ...

. Other less common names include "T-bane", which stands for "tunnelbana" (in Scandinavia, literally ''tunnel track'') and "MTR" (mass transit railway).

Monorail

A monorail is a railway in which the track consists of a single rail, as opposed to the traditional track with two parallel

rails Rail or rails may refer to: Rail transport *Rail transport and related matters *Rail (rail transport) or railway lines, the running surface of a railway Arts and media Film * ''Rails'' (film), a 1929 Italian film by Mario Camerini * ''Rail'' ( ...

Commuter rail

B set departing Panania 20180919 01 (Nimed)

A commuter rail,

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 ...

or suburban rail system operates on mainline trackage, which may be shared with intercity rail and

freight train Rail freight transport is the use of railroads and trains to transport cargo as opposed to human passengers. A freight train, cargo train, or goods train is a group of freight cars (US) or goods wagons (International Union of Railways) haul ...

s. Systems tend to operate at lower frequencies than rapid transit or light rail systems but tend to travel at higher speeds, have more widely spaced stations and cover longer overall distances. They have high passenger capacities per single train. Though many European and East Asian commuter rail systems operate with frequencies and rolling stock similar to that of rapid transit, they do not qualify as such because they share tracks with intercity/freight trains, or they have at grade crossings. For example, S-trains are hybrid systems combining the characteristics of both rapid transit and commuter rail systems. Generally, S-trains share tracks with mainline passenger and freight trains, but the distances between stations and the service headway resemble metro systems.

AGT

Automated Guideway Transit systems tend to operate with medium passenger capacities.

Funicular

A funicular is a cable-driven inclined railway that uses the weight of descending cars to help pull the ascending cars up the slope.

Cable car

A cable car, in the context of mass transit, is a system using rail cars that are hauled by a continuously-moving cable that runs at a constant speed. Individual cars stop and start by releasing and gripping the cable as required. Cable cars are distinct from funiculars (whose cars are permanently attached to the cable) and cable railways (which are similar to funiculars but have rail vehicles that are attached and detached manually).

Classification issues

Transit agencies' names for lines do not necessarily reflect their technical categorization. For example,

Boston Boston (), officially the City of Boston, is the state capital and most populous city of the Commonwealth of Massachusetts, as well as the cultural and financial center of the New England region of the United States. It is the 24th- mo ...

's Green Line is referred to as a ''subway'' although it is mostly made up of above-ground portions. Conversely, the

Docklands Light Railway The Docklands Light Railway (DLR) is an automated light metro system serving the redeveloped Docklands area of London, England and provides a direct connection between London's two major financial districts, Canary Wharf and the City of Lo ...

in London, Green Line in Los Angeles, and some metro lines in China are referred to as "Light Rail" but qualify as rapid transit because they are fully grade-separated and provide a high frequency of service. Many cities use names such as ''subway'' and ''elevated railway'' to describe their entire systems, even if they combine both methods of operation. Slightly less than half of the

London Underground The London Underground (also known simply as the Underground or by its nickname the Tube) is a rapid transit system serving Greater London and some parts of the adjacent counties of Buckinghamshire, Essex and Hertfordshire in England. The ...

's tracks, for example, are actually underground.

New York City New York, often called New York City or NYC, is the List of United States cities by population, most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the L ...

's subway also combines elevated and subterranean stations, and 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 ...

and

Vancouver SkyTrain SkyTrain is the medium-capacity rapid transit system in the Metro Vancouver Regional District, serving Vancouver, British Columbia, Canada. SkyTrain has of track and uses fully automated trains on grade-separated tracks running on underground ...

use tunnels to run through central areas.

Other types of services

Guided bus

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 ...

shares many characteristics with light rail and trams but does not run on rails.

Trolleybus A trolleybus (also known as trolley bus, trolley coach, trackless trolley, trackless tramin the 1910s and 1920sJoyce, J.; King, J. S.; and Newman, A. G. (1986). ''British Trolleybus Systems'', pp. 9, 12. London: Ian Allan Publishing. .or trol ...

es are buses that are powered from

overhead wire An overhead line or overhead wire is an electrical cable that is used to transmit electrical energy to electric locomotives, trolleybuses or trams. It is known variously as: * Overhead catenary * Overhead contact system (OCS) * Overhead equipm ...

s. Vehicles that can travel both on rails and on roads have been tried experimentally but are not in common use. The term

is used to refer to various methods of providing faster bus services and the systems that use it have similar characteristics to light rail.

Guided bus Guided buses are buses capable of being steered by external means, usually on a dedicated track or roll way that excludes other traffic, permitting the maintenance of schedules even during rush hours. Unlike trolleybuses or rubber-tired tra ...

es are buses capable of being steered by external means, usually on a dedicated track or

roll way A roll way or running pad is the pad placed on a concrete slab or on the ties on the outside of the conventional track along both running rails of a rubber-tyred metro or along the unconventional track of a tram. The rubber-tyred wheels roll d ...

that excludes other traffic. Some cities experimenting with guided bus technologies, such as Nancy, have chosen to refer to them as 'trams on tires' ( rubber-tired trams) and given them tram-like appearances.

Economics

In a 2006 article, the political scientist Ted Balaker and the urban planner Cecilia Juong Kim stated that public rail transit provides certain benefits for a community but also that the goals of policymakers are not often met. They also note some American economists claim that contrary to popular belief, rail transit has failed to improve the environment, serve the poor, or reduce highway congestion in the United States. They also claim economists are somewhat more optimistic about rail transit's impact on economic development.