Urban rail transit is a wide term for various types of local rail systems providing passenger service within and around urban or

suburb A suburb (more broadly suburban area) is an area within a metropolitan area. They are oftentimes where most of a metropolitan areas jobs are located with some being predominantly residential. They can either be denser or less densely populated ...

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), with a relatively-low capacity and frequent stops; however, modern trams have a greater passenger capacity than traditional trams. Passengers usually board at the street or curb level, but low-floor trams may allow level boarding. Longer-distance lines are called ''

interurban The interurban (or radial railway in Canada) is a type of electric railway, with tram-like electric self-propelled railcars which run within and between cities or towns. The term "interurban" is usually used in North America, with other terms u ...

s'' or ''radial railways''. Modern trams also operate as self-propelled trains coupled through a

multiple unit A multiple-unit train (or multiple unit (MU)) is a self-propelled train composed of one or more Coach (rail), carriages joined, and where one or more of the carriages have the means of propulsion built in. By contrast, a locomotive-hauled ...

instead of individual trams and are often included within the broader term

light rail Light rail (or light rail transit, abbreviated to LRT) is a form of passenger urban rail transit that uses rolling stock derived from tram technology National Conference of the Transportation Research Board while also having some features from ...

; however, they differ in that trams frequently share the platform with vehicular traffic and do not have signal priority. 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 , which literally translates as "street train" or "street railway".

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 separated from automobile traffic, but it is not, unlike rapid transit, fully grade-separated from other traffic. Light rail also generally operates with multiple-unit 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 especially in Americas, but German systems are called , which translates to "city railway". Additionally "

tram-train A tram-train or dual-system tram is a type of light rail vehicle that both meets the standards of a light rail system, and also national mainline standards. Tramcars are adapted to be capable of running on streets like an urban tramway but a ...

" systems are called and " semi-metro" systems are called or .

Rapid transit

rapid transit Rapid transit or mass rapid transit (MRT) or heavy rail, commonly referred to as metro, is a type of high-capacity public transport that is generally built in urban areas. A grade separation, grade separated rapid transit line below ground su ...

system is a

railway Rail transport (also known as train transport) is a means of transport using wheeled vehicles running in railway track, tracks, which usually consist of two parallel steel railway track, rails. Rail transport is one of the two primary means of ...

, usually in an

urban area An urban area is a human settlement with a high population density and an infrastructure of built environment. Urban areas originate through urbanization, and researchers categorize them as cities, towns, conurbations or suburbs. In urbani ...

, with high passenger capacities and frequency of service and (usually) full grade separation from other traffic, including other rail traffic. It is sometimes known as "heavy rail" to distinguish it from light rail. Both heavy and light often refer to the capacity and sometimes to investment costs. 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 is the Cities of Scotland, most populous city in Scotland, located on the banks of the River Clyde in Strathclyde, west central Scotland. It is the List of cities in the United Kingdom, third-most-populous city in the United Kingdom ...

and in

Toronto Toronto ( , locally pronounced or ) is the List of the largest municipalities in Canada by population, most populous city in Canada. It is the capital city of the Provinces and territories of Canada, Canadian province of Ontario. With a p ...

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

Taipei , nickname = The City of Azaleas , image_map = , map_caption = , pushpin_map = Taiwan#Asia#Pacific Ocean#Earth , coordinates = , subdivision_type = Country ...

Chennai Chennai, also known as Madras (List of renamed places in India#Tamil Nadu, its official name until 1996), is the capital city, capital and List of cities in Tamil Nadu by population, largest city of Tamil Nadu, the southernmost states and ...

and

Singapore Singapore, officially the Republic of Singapore, is an island country and city-state in Southeast Asia. The country's territory comprises one main island, 63 satellite islands and islets, and one outlying islet. It is about one degree ...

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

Chicago Chicago is the List of municipalities in Illinois, most populous city in the U.S. state of Illinois and in the Midwestern United States. With a population of 2,746,388, as of the 2020 United States census, 2020 census, it is the List of Unite ...

, or "Skytrain", as in

Bangkok Bangkok, officially known in Thai language, 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 estim ...

and

Vancouver Vancouver is a major city in Western Canada, located in the Lower Mainland region of British Columbia. As the List of cities in British Columbia, most populous city in the province, the 2021 Canadian census recorded 662,248 people in the cit ...

. 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 * Railway track or railway lines, the running surface of a railway Arts and media Film * ''Rails'' (film), a 1929 Italian film by Mario Camerini * ''Rail'' (1967 fi ...

. The term possibly comes from 1897, from German engineer Eugen Langen, who called an elevated railway system with wagons suspended the '' Eugen Langen One-railed Suspension Tramway'' (Einschieniges Hängebahnsystem Eugen Langen).

Commuter rail

A commuter rail,

regional rail Regional rail is a public transport, public rail transport service that operates between towns and cities. These trains operate with more stops than inter-city rail, and unlike commuter rail, operate beyond the limits of urban areas, connectin ...

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

Automated guideway transit

Automated guideway transit systems tend to operate with medium passenger capacities. Larger systems span a variety of conceptual designs, from subway-like advanced rapid transit (ART) systems to smaller (typically two to six passengers) vehicles known as personal rapid transit (PRT) which offer direct point-to-point travel along a switched network.

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. The term ''funicular'' derives from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

word , the diminutive of , meaning 'rope'.

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, the Green Line in

Boston Boston is the capital and most populous city in the Commonwealth (U.S. state), Commonwealth of Massachusetts in the United States. The city serves as the cultural and Financial centre, financial center of New England, a region of the Northeas ...

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 medium-capacity rail system, light metro system primarily serving the redeveloped London Docklands, Docklands area of London and providing a direct connection between London's two major financi ...

London London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...

, C Line in

Los Angeles Los Angeles, often referred to by its initials L.A., is the List of municipalities in California, most populous city in the U.S. state of California, and the commercial, Financial District, Los Angeles, financial, and Culture of 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 transportation. Slightly less than half of the

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

's tracks, for example, are actually underground. The

New York City Subway The New York City Subway is a rapid transit system in New York City serving the New York City boroughs, boroughs of Manhattan, Brooklyn, Queens, and the Bronx. It is owned by the government of New York City and leased to the New York City Tr ...

also combines elevated and subterranean stations, and the

Chicago "L" The Chicago "L" (short for "elevated railway, elevated") is the rapid transit system serving the city of Chicago and some of its surrounding suburbs in the U.S. state of Illinois. Operated by the Chicago Transit Authority (CTA), it is the four ...

and the Vancouver SkyTrain use tunnels to run through central areas.

Other types of services

Guided bus

A bus 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 troll ...

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, electric multiple units, trolleybuses or trams. The generic term used by the International Union of Railways for the te ...

s. Vehicles that can travel both on rails and on roads have been tried experimentally but are not in common use. The term bus rapid transit is used to refer to various methods of providing faster bus services and the systems that use it have similar characteristics to

Guided bus Guided buses are buses capable of being steered by external means, usually on a Bus lane, dedicated track or roll way that excludes other traffic, permitting the maintenance of Public transport timetable, schedules even during rush hours. Unl ...

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