page_title: Rapid transit
section_title: Modal tradeoffs and interconnections
hierarchical_section_title: Rapid transit / Modal tradeoffs and interconnections
caption_attribution_description: Homeward passengers during the evening peak hour scurry from a Central Line 1992 tube stock train (heading for Hainault via Newbury Park) on platform 6 to catch a Class 315 mainline train operated by First Great Eastern (calling at Ilford, Romford and then all stations to Shenfield) on platform 8 at Stratford station, London. Platform 7 is a disused bay (located at the far end of this island platform) which was intended for services to Fenchurch Street. At least two trains per hour between Liverpool Street and Shenfield during peak hours call at Stratford, Ilford, Romford, Gidea Park, Harold Wood, Brentwood and Shenfield. Since this photograph was taken this platform has been partially rebuilt and the gap between trains is wider, plus there is a new platform roof.
context_page_description: Rapid transit or mass rapid transit, also known as heavy rail, metro, subway, tube, U-Bahn, metropolitana or underground, is a type of high-capacity public transport generally found in urban areas. Unlike buses or trams, rapid transit systems are electric railways that operate on an exclusive right-of-way, which cannot be accessed by pedestrians or other vehicles of any sort, and which is often grade-separated in tunnels or on elevated railways.
  Modern service on rapid transit systems are provided on designated lines between stations typically using electric multiple units on rail tracks, although some systems use guided rubber tires, magnetic levitation, 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.
context_section_description: 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.
  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 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, MetroSur of the Madrid Metro, 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, Los Teques Metro and Seoul Subway Line 7, etc.) serving bi- and multi-nucleus agglomerations.
  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, 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 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. 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.
caption: Stratford Station in London is shared by London Underground trains (left) and main line rail services (right), as well as the Docklands Light Railway (not shown).
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