mover (APM) is a type of driverless grade-separated, mass-transit system. The term is generally used only to describe systems that serve as loops or feeder systems, but is sometimes applied to considerably more complex automated systems. Similar to monorails, Bombardier Innovia APM technology uses only one rail to guide the vehicle along the guideway. APMs are common at airports and effective at helping passengers quickly reach their gates. Several elevated APM systems at airports including the PHX Sky Train at Phoenix Sky Harbor International Airport; AeroTrain at Kuala Lumpur International Airport; and the Tracked Shuttle System at London Gatwick Airport, United Kingdom. Modern systems Full metro system Americas Baltimore Metro (west of Mondawmin) BART (partial) Chicago "L" (except for parts of the Red Line and Blue Line) Cleveland Red Line (partial) Guadalajara light rail system Line 3 (partial under construction) Honolulu Rail Transit (under construction light metro) MARTA (partial) Medellín Metro Mexico City Metro (partial) Miami Metrorail New York City Subway (partial) Market–Frankford Line (underground in downtown Philadelphia and West Philadelphia up to 40th Street Station but elevated elsewhere) PATCO (partial) PATH (partial) Line 3 Scarborough, a medium capacity metro rail line in Toronto, Ontario, Canada SkyTrain, Vancouver, British Columbia, Canada. Washington Metro (partial) Santiago Metro (partial) Lima Metro (partial) Asia Bangalore metro Chennai Metro (partial) Chennai Mass Rapid Transit System Delhi Metro (Yellow Line)(Green Line),(Red Line) Hanoi Metro Hong Kong MTR (Kwun Tong Line, Tsuen Wan Line, Tuen Ma Line, East Rail Line, South Island Line and Tung Chung Line) (all partial) Hyderabad Metro Kochi Metro Kolkata Metro (future line 5 & 6, later is under construction) Lahore Metro (Orange Line) Manila Light Rail Transit System Mumbai Metro Mumbai Monorail Nagpur Metro Rapid Metro Gurgaon Rapid Rail, the operator of the rapid transit (metro) system serving Kuala Lumpur and the Klang Valley area in Malaysia. BTS Skytrain, two elevated rapid transit lines in Bangkok, Thailand Wenhu line, Taipei, Taiwan Europe Berlin U-Bahn (U1 and U2 lines) Copenhagen Metro Docklands Light Railway (partial) Frankfurt U-Bahn: U1 (partial) Hamburg U-Bahn (U3 line) Paris Metro (Line 1, Line 2, Line 5, Line 6, Line 8 and Line 13) (all partial) Vienna U-Bahn (U6 line) Wuppertal Suspension Railway Stockholm Metro (Slussen-Gamla Stan) Oceania Melbourne Metro Sydney Metro Northwest Line in Sydney, Australia (skytrain section) Disused Boston Elevated Railways - Atlantic Avenue Elevated, Charlestown Elevated, Washington Street Elevated, Causeway Street Elevated Elevated railways operated