Train types

An electric locomotive draws its energy from an external supply, usually an overhead catenary or a third rail, and converts it into traction through electric motors. Because it carries neither fuel nor engine, it offers a very high power-to-weight ratio, strong acceleration and no local emissions.

A diesel locomotive carries its own power plant and can run on any line, electrified or not. In most cases the diesel engine drives a generator or alternator that feeds electric traction motors (diesel-electric transmission). Smaller locomotives and shunters often use hydraulic or mechanical transmissions instead.

Steam locomotives powered the railways from the early 19th century until their gradual replacement by diesel and electric traction after the Second World War. Water is heated in a boiler by burning coal, wood or oil, and the steam drives pistons connected to the driving wheels.

An electric multiple unit (EMU) is a self-propelled trainset in which the traction equipment is distributed along the train instead of being concentrated in a locomotive. It has a driving cab at each end and can be coupled to other units to form longer trains.

A diesel multiple unit (DMU) is a self-propelled passenger train powered by diesel engines placed under the floor or in the cars themselves. DMUs serve regional and rural lines that are not electrified, where running a locomotive-hauled train would be too costly.

Trams, also known as streetcars or light rail vehicles, run on tracks laid in the street or on reserved alignments in cities. They are usually supplied with 600 or 750 V direct current from an overhead wire.

A railcar is a single self-propelled passenger vehicle, often able to run alone or coupled with a trailer. Railcars became popular from the 1920s and 1930s on lightly used branch lines, where they were much cheaper to operate than a steam train.

Hybrid trains combine two energy sources, typically a diesel engine and a battery, or an electric supply with an on-board engine or battery for non-electrified sections. The battery recovers braking energy and allows the engine to run at its most efficient speed.

Hydrogen trains use fuel cells that combine hydrogen with oxygen from the air to produce electricity, with water vapour as the only exhaust. They offer an alternative to diesel traction on lines where electrification would be too expensive.

Gas turbine trains use a turbine, often derived from aviation, to drive a generator or a mechanical transmission. Turbines offer a high power-to-weight ratio but consume a lot of fuel, especially at partial load.

A control car, also called a driving trailer or cab car, is an unpowered vehicle fitted with a driver's cab. Placed at the opposite end of the train from the locomotive, it allows push-pull operation: the driver controls the locomotive remotely, so the train can reverse at terminal stations without the locomotive having to run around it.

Service vehicles keep the railway running: track maintenance machines, inspection and measurement trains, overhead line maintenance cars, snowploughs, cranes, rescue vehicles and shunting tractors. Some are self-propelled, others are hauled by locomotives.

A slug is a locomotive unit fitted with traction motors but without a prime mover. It receives electric power from a coupled “mother” locomotive, adding tractive effort at low speed for yard work, hump shunting or heavy trains on steep grades. Slugs are mainly used in North America.

A funicular is a cable railway built on a steep slope, in which two counterbalanced cars attached to the same cable move in opposite directions. Funiculars serve mountain resorts and hilly cities such as Lisbon, Budapest, Valparaíso or Zurich.