Before locomotives, the motive force for railways had been generated by various lower-technology methods such as human power, horse power,
gravity, or stationary engines that drove cable systems. Few such systems still exist today. Locomotives may generate their power from fuel (wood, coal, petroleum, or natural gas), or they may take
power from an outside source of electricity. It is common to classify locomotives by their source of energy. The common ones include:
Steam A steam locomotive is a locomotive whose primary power source is a
steam engine. The most common form of steam locomotive also contains a
boiler to generate the steam used by the engine. The water in the boiler is heated by burning combustible material – usually coal, wood, or oil – to produce steam. The steam moves reciprocating
pistons which are connected to the locomotive's main wheels, known as the "
driving wheels". Both fuel and water supplies are carried with the locomotive, either on the locomotive itself in
bunkers and
tanks (this arrangement is known as a "
tank locomotive"), or pulled behind the locomotive in one or more
tenders (this arrangement is known as a "
tender locomotive"). The first full-scale working railway steam locomotive was built by
Richard Trevithick in 1802. It was constructed for the
Coalbrookdale ironworks in
Shropshire, England, though no record of it operating there has survived. On 21 February 1804, the first recorded steam-hauled railway journey took place as another of Trevithick's locomotives hauled a train from the
Penydarren ironworks, in
Merthyr Tydfil, to
Abercynon in South Wales. Accompanied by
Andrew Vivian, it ran with mixed success. The design incorporated many important innovations, including the use of high-pressure steam, which reduced the weight of the engine and increased its efficiency. In 1812,
Matthew Murray's twin-cylinder
rack locomotive Salamanca first ran on the
edge-railed rack-and-pinion Middleton Railway; this is generally regarded as the first commercially successful locomotive. Another well-known early locomotive was
Puffing Billy, built 1813–14 by engineer
William Hedley for the Wylam Colliery near
Newcastle upon Tyne. This locomotive is the oldest preserved and is on static display in the Science Museum, London.
George Stephenson built
Locomotion No. 1 for the
Stockton & Darlington Railway in the north-east of England, which was the first public steam railway in the world. In 1829, his son Robert built
The Rocket in Newcastle upon Tyne. Rocket was entered into, and won, the
Rainhill Trials. This success led to the company emerging as the pre-eminent early builder of steam locomotives for railways in the UK, the US, and much of Europe. The
Liverpool & Manchester Railway, built by Stephenson, opened a year later making exclusive use of steam power for passenger and
goods trains. The steam locomotive remained by far the most common type of locomotive until after
World War II. Steam locomotives are less efficient than modern diesel and electric locomotives, and a significantly larger workforce is required to operate and service them.
British Rail figures showed that the cost of crewing and fuelling a steam locomotive was about two and a half times larger than the cost of supporting an equivalent diesel locomotive; the daily mileage they could run was lower. Between about 1950 and 1970, the majority of steam locomotives were retired from commercial service and replaced with electric and diesel–electric locomotives. While North America transitioned from steam during the 1950s, and continental Europe by the 1970s, in other parts of the world, the transition happened later. Steam was a familiar technology that used widely available fuels and, in low-wage economies, did not suffer as wide a cost disparity. It continued to be used in many countries until the end of the 20th century. By the end of the 20th century, almost the only steam power still in regular use worldwide was on
heritage railways. {{gallery
Internal combustion , 1924 in
Kyiv Internal combustion locomotives use an
internal combustion engine, connected to the
driving wheels by a transmission. They typically keep the engine running at a near-constant speed, whether the locomotive is stationary or moving. Internal combustion locomotives are categorised by fuel type and sub-categorised by transmission type. The first internal combustion rail vehicle was a
kerosene-powered
draisine built by
Gottlieb Daimler in 1887, but this was not technically a locomotive as it carried a payload. The earliest
gasoline locomotive in the western United States was built by the
Best Manufacturing Company in 1891 for
San Jose and Alum Rock Railroad. It was only a limited success and was returned to Best in 1892. The first commercially successful
petrol locomotive in the United Kingdom was a
petrol–mechanical locomotive built by the
Maudslay Motor Company in 1902, for the Deptford Cattle Market in
London. It was an 80 hp locomotive with a three-cylinder vertical petrol engine and a two-speed mechanical gearbox. In 1903, the Hungarian
Weitzer railmotor was the world's first
petrol electric locomotive.
Diesel Diesel locomotives are powered by
diesel engines. In the early days of diesel propulsion development, various transmission systems were employed with varying degrees of success, and electric transmission proved the most popular. In 1914,
Hermann Lemp, a
General Electric electrical engineer, developed and patented a reliable
direct current electrical control system (subsequent improvements were also patented by Lemp). Lemp's design used a single lever to control both engine and generator in a coordinated fashion. It was the
prototype for all
diesel–electric locomotive control. In 1917–18, GE produced three experimental diesel–electric locomotives using Lemp's control design. In 1924, a diesel–electric locomotive (
Eel2 original number Юэ 001/Yu-e 001) started operations. It was designed by a team led by
Yury Lomonosov and built in 1923–1924 by
Maschinenfabrik Esslingen in Germany. It had five driving axles (1'E1'). After several test rides, it hauled trains for almost three decades from 1925 to 1954.
Electric electric locomotive was introduced in 1925 in the
Dutch East Indies, now
Indonesia. An electric locomotive is a locomotive powered only by electricity. Electricity is supplied to moving trains with a (nearly) continuous
conductor running along the track that usually takes one of three forms: an
overhead line, suspended from poles or towers along the track or from structure or tunnel ceilings; a
third rail mounted at track level; or an onboard
battery. Both overhead wire and third-rail systems usually use the running rails as the return conductor, but some systems use a separate fourth rail for this purpose. The type of electrical power used is either
direct current (DC) or
alternating current (AC). was equipped with both a pantograph and contact shoes. Various collection methods exist: a
trolley pole, which is a long flexible pole that engages the line with a wheel or shoe; a
bow collector, which is a frame that holds a long collecting rod against the wire; a
pantograph, which is a hinged frame that holds the collecting shoes against the wire in a fixed geometry; or a
contact shoe, which is a shoe in contact with the third rail. Of the three, the pantograph method is best suited for high-speed operation. Electric locomotives almost universally use axle-hung traction motors, with one motor for each powered axle. In this arrangement, one side of the motor housing is supported by plain bearings riding on a ground-and-polished journal integral to the axle. The other side of the housing has a tongue-shaped protuberance that engages a matching slot in the truck (bogie) bolster, serving as both a torque reaction device and a support. Power transfer from motor to axle is effected by
spur gearing, in which a
pinion on the motor shaft engages a
bull gear on the axle. Both gears are enclosed in a liquid-tight housing containing lubricating oil. The type of service in which the locomotive is used dictates the gear ratio employed. Numerically high ratios are commonly found on freight units, whereas numerically low ratios are typical of passenger engines. Electricity is typically generated in large and relatively efficient
generating stations, transmitted to the railway network, and distributed to the trains. Some electric railways have their own dedicated generating stations and
transmission lines, but most purchase power from an
electric utility. The railway usually provides its own distribution lines, switches, and
transformers. Electric locomotives usually cost 20% less than diesel locomotives; their maintenance costs are 25–35% lower, and they cost up to 50% less to run.
Direct current The earliest systems were
DC systems. The first electric passenger train was presented by
Werner von Siemens at
Berlin in 1879. The locomotive was driven by a 2.2 kW, series-wound motor, and the train, consisting of the locomotive and three cars, reached a speed of 13 km/h. During four months, the train carried 90,000 passengers on a circular track. The electricity (150 V DC) was supplied through a third insulated rail between the tracks. A contact roller was used to collect the electricity. The world's first electric tram line opened in Lichterfelde near Berlin, Germany, in 1881. It was built by Werner von Siemens (see
Gross-Lichterfelde Tramway and
Berlin Straßenbahn). The
Volk's Electric Railway opened in 1883 in Brighton, and is the oldest surviving electric railway. Also in 1883, the
Mödling and Hinterbrühl Tram opened near Vienna, Austria. It was the first in the world to be in regular service, powered from an overhead line. Five years later, in the U.S. electric
trolleys were pioneered in 1888 on the
Richmond Union Passenger Railway, using equipment designed by
Frank J. Sprague. The first electrically worked
underground line was the
City & South London Railway, prompted by a clause in its enabling act prohibiting the use of steam power. It opened in 1890, using electric locomotives built by
Mather & Platt. Electricity quickly became the power supply of choice for subways, abetted by Sprague's invention of
multiple-unit train control in 1897. The first use of electrification on a main line was on a four-mile stretch of the
Baltimore Belt Line of the
Baltimore & Ohio (B&O) in 1895, connecting the main portion of the B&O to the new line to New York through a series of tunnels around the edges of Baltimore's downtown. Three
Bo+Bo units were initially used, at the south end of the electrified section; they coupled onto the locomotive and train and pulled it through the tunnels. DC was used on earlier systems. AC gradually replaced these systems. Today, almost all main-line railways use AC systems. DC systems are mostly confined to urban transit, such as metro systems, light rail, and trams, where power requirements are lower.
Alternating current The first practical
AC electric locomotive was designed by
Charles Brown, then working for the
Oerlikon in Zürich. In 1891, Brown had demonstrated long-distance power transmission using
three-phase AC between a
hydroelectric plant at
Lauffen am Neckar and
Frankfurt am Main West, a distance of 280 km. Using experience he had gained while working for
Jean Heilmann on steam–electric locomotive designs, Brown observed that
three-phase motors had a higher power-to-weight ratio than
DC motors and, because of the absence of a
commutator, were simpler to manufacture and maintain. However, they were much larger than the DC motors of the time and could not be mounted in underfloor
bogies: they could only be carried within locomotive bodies. In 1894, Hungarian engineer
Kálmán Kandó developed a new type of 3-phase asynchronous electric drive motors and generators for electric locomotives. The new 3-phase asynchronous electric drive motors were more effective than the synchronous motors used in earlier locomotive designs. Kandó's early 1894 designs were first applied in a short three-phase AC tramway in Evian-les-Bains (France), which was constructed between 1896 and 1898. In 1918, Kandó invented and developed the
rotary phase converter, enabling electric locomotives to use three-phase motors whilst supplied via a single overhead wire, carrying the simple industrial frequency (50 Hz) single phase AC of the high voltage national networks. In 1896, Oerlikon installed the first commercial system on the
Lugano Tramway. Each 30-tonne locomotive had two motors run by three-phase 750 V 40 Hz fed from double overhead lines. Three-phase motors run at constant speed and provide
regenerative braking, and are well suited to steeply graded routes. The first main-line three-phase locomotives were supplied by Brown (by then in partnership with
Walter Boveri) in 1899 on the 40 km
Burgdorf—Thun line, Switzerland. The first implementation of industrial frequency single-phase AC supply for locomotives came from Oerlikon in 1901, using the designs of
Hans Behn-Eschenburg and
Emil Huber-Stockar; installation on the Seebach-Wettingen line of the Swiss Federal Railways was completed in 1904. The 15 kV, 50 Hz , 48 tonne locomotives used transformers and rotary converters to power DC traction motors. Italian railways were the first in the world to introduce electric traction for the entire length of a main line rather than just a short stretch. The 106 km Valtellina line was opened on 4 September 1902 and was designed by Kandó and a team from the Ganz works. The three-phase two-wire system was used on several railways in Northern Italy and became known as "the Italian system". Kandó was invited in 1905 to manage Società Italiana Westinghouse and led the development of several Italian electric locomotives. Battery locomotives in over-the-road service can recharge while absorbing dynamic-braking energy. The first known electric locomotive was built in 1837 by chemist
Robert Davidson of
Aberdeen, and it was powered by
galvanic cells (batteries). Davidson later built a larger locomotive named
Galvani, exhibited at the
Royal Scottish Society of Arts Exhibition in 1841. The vehicle had two
direct-drive reluctance motors, with fixed electromagnets acting on iron bars attached to a wooden cylinder on each axle, and simple
commutators. It hauled a load of at for a distance of . It was tested on the
Edinburgh and Glasgow Railway in September of the following year, but the limited power from batteries prevented its general use. Another example was the
Kennecott Copper Mine,
Latouche, Alaska, where in 1917 the underground haulage ways were widened to enable working by two battery locomotives. In 1928, Kennecott Copper ordered four 700-series electric locomotives with on-board batteries. These locomotives weighed and operated on 750-volt overhead trolley wire with considerable further range whilst running on batteries. The locomotives provided several decades of service using
Nickel–iron battery (Edison) technology. These were later replaced with
lead-acid batteries, and the locomotives were retired shortly afterward. All four locomotives were donated to museums, but one was scrapped. The others can be seen at the
Boone and Scenic Valley Railroad in Iowa and at the
Western Railway Museum in Rio Vista, California. The
Toronto Transit Commission previously operated a battery-electric locomotive built by
Nippon Sharyo in 1968, which was retired in 2009. London Underground regularly operates
battery–electric locomotives for general maintenance work.
Other types Fireless Atomic–electric In the early 1950s, Lyle Borst of the
University of Utah received funding from various US railroad lines and manufacturers to study the feasibility of an electric-drive locomotive in which an onboard atomic reactor produced steam to generate electricity. At that time, atomic power was not fully understood; Borst believed the biggest issue was the price of uranium. With his atomic locomotive, the center section would have a reactor chamber and steel walls thick to prevent radiation leaks in the event of an accident. He estimated a cost to manufacture atomic locomotives with engines at approximately $1,200,000 each. Consequently, trains with onboard nuclear generators were generally deemed unfeasible due to prohibitive costs.
Fuel cell–electric In 2002, the first ,
hydrogen-(fuel-cell)–powered mining locomotive was demonstrated in
Val-d'Or,
Quebec. In 2007, the educational mini-hydrail in
Kaohsiung,
Taiwan, entered service. The
Railpower GG20B is another example of a fuel cell–electric locomotive.
Hybrid locomotives , at the Innotrans convention in
Berlin There are many types of hybrid or dual-mode locomotives that use two or more types of motive power. The most common hybrids are
electro-diesel locomotives powered either from an electricity supply or else by an onboard
diesel engine. These are used to provide continuous journeys along routes that are only partly electrified. Examples include the
EMD FL9 and
Bombardier ALP-45DP ==Use==