Metro

This page refersurban rail mass transit systems. For other uses see metro (disambiguation).

Underground, subwaymetrocommon names forformmass transit public transport system employing small trains, thesealso calledBritain tube trains. In many cases, at leastportion ofrailsplacedtunnels dug beneathsurface ofcity. [1]

One definition of"true" metro systemas follows:

1. an urban, electric mass transit system
2. totally independent from other traffic
3. with high service frequency.

This definition does not mention whethertrain runs underground or above-ground. Since many such systems have above-ground portions, "metro" can be used asgeneralized term that includes systemssystem portions thatelevated or at grade (avoidingnecessarily subterranean connotations"underground" or "subway".) In some cities, "subway"used onlythat portion ofparticular system that actuallyunderground.

Formore comprehensive listingother namesthis kindsystemcities aroundworld, seelistmetro systems.

The metro trains usually stop at short intervalslet passengers on or off. The volumepassengersmetro train can carryoften quite high, andmetro systemoften viewed asbackbone oflarge city's public transportation system.

Traditionally, metro trainsdriven by human drivers, but automated trains also exist, in,example, London (the Victoria Line), Singapore, and Paris. Thisnotrecent invention; operationtrains onVictoria Line has been automatic since its opening1968. However,commonmost systems, an operatorstill carried incab atfront oftrain. The VAL (véhicule automatique léger)Lille, inaugurated1983, providedfirst driverless underground system. Other driverless lines now includeline 14 (Meteor) ofParis Metro, opened1998. The Docklands Light Railway (1987)London, whilst formost part not underground,also driverless. See also People mover.

The constructionan undergroundan expensive project, often carried out overnumberyears. Several modestunneling exist. One common method isplacetracks directly beneathcity streets, upholdingroads by structural columnssteel, concrete, or, inoldest systems, cast iron (most ofbelow-ground part ofNew York Subway systemconstructedthis manner, known as cut-and-cover). Another usual way isdigtunnels (oftentunnelling shield) beneath previously occupied subterranean space, through native bedrock,sealtunnels from leakageground waterconcrete.

Underground systems usevarietytechnologies. Most systems run on steel wheelsrails, although many modern systems use rubber tiresconcrete rollways. (The Montreal metro wasfirst completely rubber-tired underground system.) Power may be supplied either by means ofthird rail (New York) or by overhead lines (Madrid). Systems may be underground, at grade, elevated, ormix as inParis metro. Some systems use light rail; other cities' systemshybrids whereintramway moves underground incity centre.

Underground systems need constant investment frompublic authority,avoid disasters like King's Cross fireLondon's underground.

An exception torule that underground trainsfor public transportation isPost Office Railway,driverless, underground railwayLondon that was used exclusivelytransport mail between sorting offices, though itnow "mothballed".

History

The oldest subway tunnel inworld isAtlantic Avenue TunnelBrooklyn, New York, built1844.

The London Underground wasfirst more extensive system.

Boston hasoldest subway system inUnited States,green line.

Asia's oldest subway lineTokyo's Ginza Line opened in 1927.

Alfred Beach's first New York Subway system usedpneumatic tube principle. It was only 300 feet long.

image:beachsub.jpg image:beachsub2.jpg

A person withdevoted interestthese systems ismetrophile.

See also Metro station, U-Bahn.

External links

• UrbanRail.Net (formerly called metroPlanet) - descriptionsall metro systems inworld, each withschematic map showing all stations
• Bucharest Metro, Romania
• "MindGap"