page_title: Rapid transit
section_title: Infrastructure
hierarchical_section_title: Rapid transit / Infrastructure
caption_attribution_description: Tunnel of the metro Turin, Italy
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: The technology used for public, mass rapid transit has undergone significant changes in the years since the Metropolitan Railway 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 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 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.
caption: Inside a tunnel on the Turin Metro, the interlocking tunnel lining segments placed by a tunnel boring machine can be clearly seen.
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