train

A train is a connected series of vehicles that run on railway tracks, typically powered by locomotives or by self-propelled multiple units. Trains may carry passengers, freight, or both, and operate on fixed rails that provide guidance and support. Rolling stock includes locomotives, passenger cars, freight wagons, and special-purpose vehicles. The infrastructure comprises tracks, stations, yards, signaling systems, and power supply networks in electrified lines.

Rail transport began in the early 19th century with steam-powered locomotives, enabling rapid expansion of networks in Europe and North America. Diesel-electric and electric traction gradually replaced steam, improving efficiency and performance. Since the 1960s, high-speed rail has demonstrated speeds exceeding 250 km/h on dedicated alignments. More recently, maglev and other technologies have been explored.

Trains operate under timetables and signaling to coordinate traffic and safety. Electrification provides power via overhead catenaries or third rails; non-electrified lines rely on onboard propulsion. Trains require maintenance of track, rolling stock, and electrical systems, and operate within national, regional, or private networks.

Types include passenger services—intercity, regional, commuter—and freight trains. Rail gauges vary by country; standard gauge of 1,435 mm is most common, with broad and narrow gauges used in some regions. High-speed trains use dedicated alignments and specialized rolling stock, while metro and light rail systems provide urban transit.

Rail offers high passenger capacity and energy efficiency per ton-kilometer and generally lower emissions than road transport when powered by renewable electricity. Capital costs, land use for right-of-way, and maintenance are major considerations in planning rail networks.