A locomotive or engine is a rail transport vehicle that provides the
motive power for a train. If a locomotive is capable of carrying a
payload, it is usually rather referred to as multiple units, motor
coaches, railcars or power cars; the use of these self-propelled
vehicles is increasingly common for passenger trains, but rare for
freight (see CargoSprinter).
Traditionally, locomotives pulled trains from the front. However,
push-pull operation has become common, where the train may have a
locomotive (or locomotives) at the front, at the rear, or at each end.
2.1 Motive power
2.1.5 Gas turbine
18.104.22.168 Direct current
22.214.171.124 Alternating current
2.1.7 Other types
2.3 Operational role
2.4 Wheel arrangement
2.5 Remote control locomotives
3 Comparison to multiple units
4 Locomotives in numismatics
5 See also
8 External links
The word locomotive originates from the Latin loco – "from a place",
ablative of locus, "place" + Medieval Latin motivus, "causing motion",
and is a shortened form of the term locomotive engine, which was
first used in the early 19th century to distinguish between mobile and
stationary steam engines.
Prior to 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 are still in existence 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:
The main components of a steam locomotive
A steam locomotive is a railway locomotive consisting of a steam
engine. These locomotives are fueled by burning combustible material
– usually coal, wood, or oil – to produce steam in a boiler. The
steam moves reciprocating pistons which are mechanically connected to
the locomotive's main wheels (drivers). Both fuel and water supplies
are carried with the locomotive, either on the locomotive itself or in
wagons (tenders) pulled behind.
Trevithick's 1802 locomotive
The first full-scale working railway steam locomotive was built by
Richard Trevithick in 1802. It was constructed for the Coalbrookdale
Shropshire in the United Kingdom though no record of it
working 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 for the
Pen-y-darren ironworks, near
Merthyr Tydfil, to
Abercynon in South Wales. Accompanied by
Andrew Vivian, it ran with mixed success. The design incorporated a
number of important innovations that included using high-pressure
steam which reduced the weight of the engine and increased its
The Locomotion No 1 at Darlington Railway Centre and Museum
In 1812, Matthew Murray's successful twin-cylinder rack locomotive
Salamanca first ran on the edge-railed rack-and-pinion Middleton
Railway. Another well-known early locomotive was Puffing Billy,
built 1813–14 by engineer William Hedley. It was intended to work on
the Wylam Colliery near Newcastle upon Tyne. This locomotive is the
oldest preserved, and is on static display in the Science Museum,
George Stephenson built
Locomotion No. 1
Locomotion No. 1 for the Stockton and
Darlington Railway, north-east England, which was the first public
steam railway in the world. In 1829, his son Robert built in Newcastle
The Rocket which was entered in and won the Rainhill Trials. This
success led to the company emerging as the pre-eminent builder of
steam locomotives used on railways in the UK, US and much of
Europe. The Liverpool and 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. The introduction of electric
locomotives around the turn of the 20th century and later
diesel-electric locomotives spelled the beginning of a decline in the
use of steam locomotives, although it was some time before they were
phased out of general use. As diesel power (especially with
electric transmission) became more reliable in the 1930s, it gained a
foothold in North America. The full transition away from steam
power in North America took place during the 1950s. In continental
Europe, large-scale electrification had replaced steam power by the
1970s. In other parts of the world, transition happened later. Steam
was a familiar technology, adapted well to local facilities, and also
consumed a wide variety of fuels; this led to its continued use in
many countries until the end of the 20th century. By the end of the
20th century, almost the only steam power remaining in regular use
around the world was on heritage railways.
Steam locomotives are less efficient than their more modern diesel and
electric counterparts and require much greater manpower to operate and
British Rail figures showed the cost of crewing and
fuelling a steam locomotive was some two and a half times that of
diesel power, and the daily mileage achievable was far too less.
A kerosene locomotive is an internal combustion engine locomotive
using kerosene as the fuel. The kerosene locomotives were the world's
first oil locomotives, preceding diesel and other oil locomotives by
A kerosene locomotive was built in 1894 by the
Priestman Brothers of
Kingston upon Hull
Kingston upon Hull for use on Hull docks. This locomotive was built
using a 12 hp double-acting marine type engine, running at 300
rpm, mounted on a 4-wheel wagon chassis. It was only able to haul one
loaded wagon at a time, due to its low power output, and was not a
great success. The first successful kerosene locomotive was
"Lachesis" built by
Richard Hornsby & Sons Ltd. and delivered to
Woolwich Arsenal railway in 1896. The company built a series of
kerosene locomotives between 1896 and 1903. These were built for use
by the British military.
The 1902 Maudslay
A petrol locomotive is a internal combustion engine locomotive
consisting of a petrol engine. ICE engines require a transmission to
power the wheels. The engine must be allowed to continue to run when
the locomotive is stopped.
Petrol-mechanical locomotives use a mechanical transmission to deliver
the power output of petrol engines to the wheels. Most petrol
locomotives built were petrol-mechanical locomotives. The first
commercially successful petrol locomotive was a petrol-mechanical
built by the
Maudslay Motor Company
Maudslay Motor Company in 1902, for the Deptford Cattle
Market in London. It was a 80 hp locomotive using a 3-cylinder
vertical petrol engine, with a two speed mechanical gearbox. The
second locomotive was built by F.C. Blake of Kew in January 1903 for
the Richmond Main Sewerage Board. In 1916 Simplex petrol
locomotives with 20-40 hp motors and 4-wheel mechanical
transmission began to be used on 600 mm
(1 ft 11 5⁄8 in) gauge trench railways on the
Western Front. The War Department also ordered larger petrol-electric
locomotives from Dick, Kerr & Co. and
British Westinghouse at the
same time: These used a 45 hp petrol engine driving a 500V
generator. Many were sold off as surplus at the end of
hostilities, finding work on small industrial railways. Motor Rail
continued to manufacture and develop the design, for the next few
Main article: Diesel locomotive
A diesel locomotive is a internal combustion engine locomotive
consisting of a diesel engine. ICE engines require a transmission to
power the wheels. The engine must be allowed to continue to run when
the locomotive is stopped. In the early days of diesel propulsion
development, various systems were all employed with varying degrees of
success. Of the three, electric transmission proved to be most
popular, and although other locomotives have certain advantages and
continue to be used, most diesel-powered locomotives today are
Schematic illustration of a diesel mechanical locomotive
An early diesel-mechanical locomotive at the North Alabama Railroad
A diesel–mechanical locomotive uses a mechanical transmission to
transfer power to the wheels. This type of transmission is generally
limited to low-powered, low speed shunting (switching) locomotives,
lightweight multiple units and self-propelled railcars. The earliest
diesel locomotives were diesel-mechanical.
The mechanical transmissions used for railroad propulsion are
generally more complex and much more robust than standard-road
versions. There is usually a fluid coupling interposed between the
engine and gearbox, and the gearbox is often of the epicyclic
(planetary) type to permit shifting while under load. Various systems
have been devised to minimise the break in transmission during gear
changing; e.g., the S.S.S. (synchro-self-shifting) gearbox used by
Hudswell Clarke. Diesel–mechanical propulsion is limited by the
difficulty of building a reasonably sized transmission capable of
coping with the power and torque required to move a heavy train.
In 1906, Rudolf Diesel,
Adolf Klose and the steam and diesel engine
Gebrüder Sulzer founded Diesel-Sulzer-Klose GmbH to
manufacture diesel-powered locomotives. The Prussian State Railways
ordered a diesel locomotive from the company in 1909. The world's
first diesel-powered locomotive (a diesel-mechanical locomotive) was
operated in the summer of 1912 on the Winterthur–Romanshorn railway
in Switzerland, but was not a commercial success. The locomotive
weight was 95 tonnes and the power was 883 kW with a maximum
speed of 100 km/h. Small numbers of prototype diesel
locomotives were produced in a number of countries through the
Schematic diagram of diesel electric locomotive
In a diesel–electric locomotive, the diesel engine drives either an
electrical DC generator (generally, less than 3,000 horsepower
(2,200 kW) net for traction), or an electrical AC
alternator-rectifier (generally 3,000 horsepower (2,200 kW) net
or more for traction), the output of which provides power to the
traction motors that drive the locomotive. There is no mechanical
connection between the diesel engine and the wheels. The vast majority
of diesel locomotives today are diesel-electric.
The important components of diesel–electric propulsion are the
diesel engine (also known as the prime mover), the main
generator/alternator-rectifier, traction motors (usually with four or
six axles), and a control system consisting of the engine governor and
electrical or electronic components, including switchgear, rectifiers
and other components, which control or modify the electrical supply to
the traction motors. In the most elementary case, the generator may be
directly connected to the motors with only very simple switchgear.
Originally, the traction motors and generator were DC machines.
Following the development of high-capacity silicon rectifiers in the
1960s, the DC generator was replaced by an alternator using a diode
bridge to convert its output to DC. This advance greatly improved
locomotive reliability and decreased generator maintenance costs by
elimination of the commutator and brushes in the generator.
Elimination of the brushes and commutator, in turn, disposed of the
possibility of a particularly destructive type of event referred to as
a flashover, which could result in immediate generator failure and, in
some cases, start an engine room fire.
World's first useful diesel locomotive (a diesel-electric locomotive)
for long distances SŽD Eel2, 1924 in Kiev
In the late 1980s, the development of high-power
variable-frequency/variable-voltage (VVVF) drives, or "traction
inverters," has allowed the use of polyphase AC traction motors, thus
also eliminating the motor commutator and brushes. The result is a
more efficient and reliable drive that requires relatively little
maintenance and is better able to cope with overload conditions that
often destroyed the older types of motors.
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, and 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 had been designed by
a team led by
Yuri Lomonosov and built 1923–1924 by Maschinenfabrik
Esslingen in Germany. It had 5 driving axles (1'E1'). After several
test rides, it hauled trains for almost three decades from 1925 to
1954. It was the world's first world's first functional diesel
DB Class V 200
DB Class V 200 diesel-hydraulic locomotive at Technikmuseum,
Diesel–hydraulic locomotives use one or more torque converters, in
combination with gears, with a mechanical final drive to convey the
power from the diesel engine to the wheels.
Hydrokinetic transmission (also called hydrodynamic transmission) uses
a torque converter. A torque converter consists of three main parts,
two of which rotate, and one (the stator) that has a lock preventing
backwards rotation and adding output torque by redirecting the oil
flow at low output RPM. All three main parts are sealed in an
oil-filled housing. To match engine speed to load speed over the
entire speed range of a locomotive some additional method is required
to give sufficient range. One method is to follow the torque converter
with a mechanical gearbox which switches ratios automatically, similar
to an automatic transmission on a car. Another method is to provide
several torque converters each with a range of variability covering
part of the total required; all the torque converters are mechanically
connected all the time, and the appropriate one for the speed range
required is selected by filling it with oil and draining the others.
The filling and draining is carried out with the transmission under
load, and results in very smooth range changes with no break in the
The main worldwide user of main-line hydraulic transmissions was the
Federal Republic of Germany, with designs including the 1950s DB class
V 200, and the 1960 and 1970s DB Class V 160 family. British Rail
introduced a number of diesel hydraulic designs during it 1955
Modernisation Plan, initially license built versions of German designs
(see Category:Diesel–hydraulic locomotives of Great Britain). In
RENFE used high power to weight ratio twin engined German
designs to haul high speed trains from the 1960s to 1990s. (see RENFE
Classes 340, 350, 352, 353, 354).
Hydraulic drive systems using a hydrostatic hydraulic drive system
have been applied to rail use. Examples included 350 to 750 hp
(260 to 560 kW) shunting locomotives by CMI Group (Belgium),
4 to 12 tonne 35 to 58 kW (47 to 78 hp) industrial
Atlas Copco subsidiary GIA. Hydrostatic drives are
also utilised in railway maintenance machines (tampers, rail
These systems are used in some rail applications, primarily low speed
shunting and rail-maintenance vehicles.
Steam diesel hybrid locomotive
A Soviet steam-diesel hybrid locomotive TP1
Steam-diesel hybrid locomotives can use steam generated from a boiler
or diesel to power a piston engine. The Cristiani Compressed Steam
System used a diesel engine to power a compressor to drive and
recirculate steam produced by a boiler; effectively using steam as the
power transmission medium, with the diesel engine being the prime
In the 1940s, diesel locomotives began to displace steam power on
American railroads. Following the end of World War II, diesel power
began to appear on railroads in many countries. The significantly
better economics of diesel operation triggered a dash to diesel power,
a process known as Dieselization. By the late 1990s, only heritage
railways continued to operate steam locomotives.
Diesel locomotives require considerably less maintenance than steam,
with a corresponding reduction in the number of personnel needed to
keep the fleet in service. The best steam locomotives spent an average
of three to five days per month in the shop for routine maintenance
and running repairs. Heavy overhauls were frequent,
often involving removal of the boiler from the frame for major
repairs. In contrast, a typical diesel locomotive requires no more
than eight to ten hours of maintenance per month (maintenance
intervals are 92 days or 184 days, depending upon a locomotive's
age), and may run for decades between major
overhauls. Diesel units do not pollute as much as
steam trains; modern units produce low levels of
Gas turbine locomotive
A gas turbine locomotive is an internal combustion engine locomotive
consisting of a gas turbine. ICE engines require a transmission to
power the wheels. The engine must be allowed to continue to run when
the locomotive is stopped.
A 44-ton 1-B-1 experimental gas turbine locomotive designed by R. Tom
Sawyer and built in 1952 for testing by the U.S. Army Transportation
Gas turbine-mechanical locomotives, use a mechanical transmission to
deliver the power output of gas turbines to the wheels. A gas turbine
locomotive was patented in 1861 by Marc Antoine Francois Mennons
(British patent no. 1633). There is no evidence that the
locomotive was actually built but the design includes the essential
features of gas turbine locomotives built in the 20th century,
including compressor, combustion chamber, turbine and air pre-heater.
In 1952, Renault delivered a prototype four-axle 1150 hp
gas-turbine-mechanical locomotive fitted with the Pescara "free
turbine" gas- and compressed-air producing system, rather than a
co-axial multi-stage compressor integral to the turbine. This model
was succeeded by a pair of six-axle 2400 hp locomotives with two
turbines and Pescara feeds in 1959. Several similar locomotives were
built in USSR by Kharkov
UP 18, a gas turbine-electric locomotive preserved at the Illinois
Gas turbine-electric locomotives, use a gas turbine to drive an
electrical generator or alternator which produced electric current
powers the traction motor which drive the wheels. In 1939 the Swiss
Federal Railways ordered Am 4/6, a GTEL with a 1,620 kW
(2,170 hp) of maximum engine power from Brown Boveri. It was
completed in 1941, and then underwent testing before entering regular
service. The Am 4/6 was the first gas turbine – electric locomotive.
British Rail 18000 was built by Brown Boveri and delivered in 1949.
British Rail 18100 was built by
Metropolitan-Vickers and delivered in
1951. A third locomotive, the
British Rail GT3, was constructed in
Union Pacific ran a large fleet of turbine-powered freight
locomotives starting in the 1950s. These were widely used on
long-haul routes, and were cost-effective despite their poor fuel
economy due to their use of "leftover" fuels from the petroleum
industry. At their height the railroad estimated that they powered
about 10% of Union Pacific's freight trains, a much wider use than any
other example of this class.
A gas turbine offers some advantages over a piston engine. There are
few moving parts, decreasing the need for lubrication and potentially
reducing maintenance costs, and the power-to-weight ratio is much
higher. A turbine of a given power output is also physically smaller
than an equally powerful piston engine, allowing a locomotive to be
very powerful without being inordinately large. However, a turbine's
power output and efficiency both drop dramatically with rotational
speed, unlike a piston engine, which has a comparatively flat power
curve. This makes GTEL systems useful primarily for long-distance
high-speed runs. Additional problems with gas turbine-electric
locomotives included that they were very noisy, and they
produced such extremely hot exhaust that if the locomotive were parked
under an overpass paved with asphalt, it could melt the asphalt.
Main article: Electric locomotive
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
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 that is 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, its purpose being to act as a
torque reaction device, as well as 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.
Werner von Siemens
Werner von Siemens experimental DC electric train, 1879
Baltimore & Ohio electric engine, 1895
Earliest systems were DC systems. The first electric passenger train
was presented by
Werner von Siemens
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 300-metre-long (984 feet) 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
Werner von Siemens (see Gross-Lichterfelde
Berlin Straßenbahn). The
Volk's Electric Railway
Volk's Electric Railway opened
in 1883 in Brighton, and is the oldest surviving electric railway.
Also in 1883,
Mödling and Hinterbrühl Tram
Mödling and Hinterbrühl Tram opened near Vienna in
Austria. It was the first in the world 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 and South
London Railway, prompted by a clause in its enabling act prohibiting
use of steam power. It opened in 1890, using electric locomotives
built by Mather and Platt. Electricity quickly became the power supply
of choice for subways, abetted by the 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
Baltimore Belt Line of the Baltimore and Ohio Railroad
(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. These systems were gradually replaced
by AC. Today, almost all main-line railways use AC systems. DC systems
are confined mostly to urban transit such as metro systems, light rail
and trams, where power requirement is less.
The first practical AC electric locomotive was designed by Charles
Brown, then working for Oerlikon, Zürich. In 1891, Brown had
demonstrated long-distance power transmission, using three-phase AC,
between a hydro-electric plant at
Lauffen am Neckar
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
In 1894, Hungarian engineer
Kálmán Kandó developed a new type
3-phase asynchronous electric drive motors and generators for electric
locomotives. 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
In 1896, Oerlikon installed the first commercial example of the system
on the Lugano Tramway. Each 30-tonne locomotive had two 110 kW
(150 hp) 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, and 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
Swiss Federal Railways was completed in 1904. The 15 kV,
50 Hz 345 kW (460 hp), 48 tonne locomotives used
transformers and rotary converters to power DC traction motors.
A prototype of a Ganz AC electric locomotive in Valtellina, Italy,
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, designed by Kandó and a team from the Ganz works. The
electrical system was three-phase at 3 kV 15 Hz. The voltage
was significantly higher than used earlier and it required new designs
for electric motors and switching devices. The three-phase
two-wire system was used on several railways in Northern
became known as "the Italian system". Kandó was invited in 1905 to
undertake the management of Società Italiana Westinghouse and led the
development of several Italian electric locomotives.
London Underground battery-electric locomotive at West Ham station
used for hauling engineers' trains
A battery-electric locomotive (or battery locomotive) is an electric
locomotive powered by on-board batteries; a kind of battery electric
Such locomotives are used where a conventional diesel or electric
locomotive would be unsuitable. An example is maintenance trains on
electrified lines when the electricity supply is turned off. Another
use is in industrial facilities where a combustion-powered locomotive
(i.e., steam- or diesel-powered) could cause a safety issue due to the
risks of fire, explosion or fumes in a confined space. Battery
locomotives are preferred for mines where gas could be ignited by
trolley-powered units arcing at the collection shoes, or where
electrical resistance could develop in the supply or return circuits,
especially at rail joints, and allow dangerous current leakage into
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 seven-ton 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 six tons at
four miles per hour (6 kilometers per hour) for a distance of one and
a half miles (2 kilometers). 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 at the Kennecott Copper Mine, Latouche, Alaska,
where in 1917 the underground haulage ways were widened to enable
working by two battery locomotives of 4 1⁄2 tons. In
1928, Kennecott Copper ordered four 700-series electric locomotives
with on-board batteries. These locomotives weighed 85 tons 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. The batteries were 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, 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 and retired in 2009.
London Underground regularly operates battery-electric locomotives for
general maintenance work.
In the 1960s, development of very high-speed service brought further
electrification. The Japanese
Shinkansen and the French
TGV were the
first systems for which devoted high-speed lines were built from
scratch. Similar programs were undertaken in Italy,
Germany and Spain;
and many countries around the world. Railway electrification has
constantly increased in the past decades, and as of 2012, electrified
tracks account for nearly one third of total tracks globally.
In comparison to the principal alternative, the diesel engine,
electric railways offer substantially better energy efficiency, lower
emissions and lower operating costs. Electric locomotives are also
usually quieter, more powerful, and more responsive and reliable than
diesels. They have no local emissions, an important advantage in
tunnels and urban areas. Some electric traction systems provide
regenerative braking that turns the train's kinetic energy back into
electricity and returns it to the supply system to be used by other
trains or the general utility grid. While diesel locomotives burn
petroleum, electricity can be generated from diverse sources including
In the early 1950s, Dr. Lyle Borst of the
University of Utah
University of Utah was given
funding by various US railroad line and manufacturers to study the
feasibility of an electric-drive locomotive, in which an onboard
atomic reactor produced the steam to generate the electricity. At that
time, atomic power was not fully understood; Borst believed the major
stumbling block was the price of uranium. With the Borst atomic
locomotive, the center section would have a 200-ton reactor chamber
and steel walls 5 feet thick to prevent releases of radioactivity in
case of accidents. He estimated a cost to manufacture atomic
locomotives with 7000 h.p. engines at approximately $1,200,000
each. Consequently, trains with onboard nuclear generators were
generally deemed unfeasible due to prohibitive costs.
Main article: Hydrail
In 2002, the first 3.6 tonne, 17 kW hydrogen (fuel cell) -powered
mining locomotive was demonstrated in Val-d'Or, Quebec. In 2007 the
educational mini-hydrail in Kaohsiung,
Taiwan went into service. The
Railpower GG20B finally is another example of a fuel cell-electric
Main article: Hybrid locomotive
There are many different types of hybrid locomotives using two or more
types of motive power.
The three main categories of locomotives are often subdivided in their
usage in rail transport operations. There are passenger locomotives,
freight locomotives and switcher (or shunting) locomotives. These
categories determine the locomotive's combination of physical size,
starting tractive effort and maximum permitted speed. Freight
locomotives are normally designed to deliver high starting tractive
effort—needed to start trains that may weigh as much as 15,000 long
tons (16,800 short tons; 15,241 t)—and deliver sustained high
power, at the sacrifice of maximum speed.
develop less starting tractive effort but are able to operate at the
high speeds demanded by passenger schedules. Mixed traffic locomotives
(US English: general purpose or road switcher locomotives) are built
to provide elements of both requirements. They do not develop as much
starting tractive effort as a freight unit but are able to haul
heavier trains than a passenger engine.
Most steam locomotives are reciprocating units, in which the pistons
are coupled to the drivers (driving wheels) by means of connecting
rods, with no intervening gearbox. Therefore, the combination of
starting tractive effort and maximum speed is greatly influenced by
the diameter of the drivers.
Steam locomotives intended for freight
service generally have relatively small diameter drivers, whereas
passenger models have large diameter drivers (as large as 84 inches or
2,134 millimetres in some cases).
With diesel-electric and electric locomotives, the gear ratio between
the traction motors and axles is what adapts the unit to freight or
passenger service, although a passenger unit may include other
features, such as head-end power (also referred to as hotel power or
electric train supply) or a steam generator.
Some locomotives are designed specifically to work steep grade
railways, and feature extensive additional braking mechanisms and
sometimes rack and pinion.
Steam locomotives built for steep rack and
pinion railways frequently have the boiler tilted relative to the
wheels, so that the boiler remains roughly level on steep grades.
Operational role 
Locomotives occasionally work in a specific role, such as:
Train engine is the technical name for a locomotive attached to the
front of a railway train to haul that train. Alternatively, where
facilities exist for push-pull operation, the train engine might be
attached to the rear of the train;
Pilot engine – a locomotive attached in front of the train engine,
to enable Double-heading;
Banking engine – a locomotive temporarily assisting a train from the
rear, due to a difficult start or a sharp incline gradient;
Light engine – a locomotive operating without a train behind it, for
relocation or operational reasons.
Station pilot – a locomotive used to shunt passenger trains at a
Main article: Wheel arrangement
Wheel arrangement is one type of classification. Common methods
include the AAR wheel arrangement, UIC classification, and Whyte
Remote control locomotives
Main article: Remote control locomotive
In the second half of the twentieth century remote control locomotives
started to enter service in switching operations, being remotely
controlled by an operator outside of the locomotive cab. The main
benefit is one operator can control the loading of grain, coal,
gravel, etc. into the cars. In addition, the same operator can move
the train as needed. Thus, the locomotive is loaded or unloaded in
about a third of the time.
Comparison to multiple units
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There are a few basic reasons to isolate locomotive train power, as
compared to self-propelled vehicles.
Whether out of necessity to replace the locomotive due to failure, or
for reason of needing to maintain the power unit, it is relatively
easy to replace the locomotive with another, while not removing the
entire train from service.
Maximum utilization of power cars
Separate locomotives facilitate movement of costly motive power assets
as needed; thereby avoiding the expense associated with tied up or
idle power resources.
Large locomotives can substitute for small locomotives when more power
is required, for example, where grades are steeper. As needed, a
locomotive can be used for either freight duties, or passenger
Separating motive power from payload-hauling cars enables replacement
of one without affecting the other. To illustrate, locomotives might
become obsolete when their associated cars are not, and vice versa.
In an accident, the locomotive may act as a buffer zone to the rest of
the train. Depending on the obstacle encountered on the rail line, the
heavier mass of a locomotive is less likely to deviate from its normal
course. In the event of fire, it might be safer, for example, with
A single source of tractive power (i.e., motors in one place), is
quieter than multiple operational power units, where one or more
motors are located under every carriage. The noise problem is
particularly noticeable in diesel multiple units.
The motive power accompanies the cars to be hauled and consequently
there is a saving in time.
Especially for steam locomotives but also for other types, maintenance
facilities can be very dirty environments and it is advantageous not
to have to take passenger accommodation into the same depot. This was
one reason for the demise of the GWR steam railmotors.
There are several advantages of multiple unit (MU) trains compared to
Multiple units are more energy efficient than locomotive-hauled trains
and more nimble, especially on down grades, as much more of the
train's weight (sometimes all of it) is placed on driven wheels,
rather than suffering the dead weight of unpowered coaches.
No need to turn the locomotive
Many multiple units have cabs at both ends; therefore, the train may
be reversed without uncoupling/re-coupling the locomotive, providing
quicker turnaround times, reduced crew costs, and enhanced safety. In
practice, the development of driving van trailers and cab cars has
removed the need for locomotives to run-around, giving easy
bi-directional operation and removing this MU advantage.
Multiple unit trains have multiple engines, where the failure of one
engine usually does not prevent the train from continuing on its
journey. A locomotive drawn passenger train typically has only a
single power unit; the failure of this single unit temporarily
disables the train. However, as is often the case with locomotive
hauled freight trains, some passenger trains utilize multiple
locomotives, and are thus able to continue at reduced speed after the
failure of one locomotive.
Locomotives in numismatics
Locomotives have been a subject for collectors' coins and medals. One
of the most famous and recent when ones is the 25
Euro 150 Years Semmering Alpine Railway commemorative coin. The
obverse shows two locomotives: a historical and a modern one. This
represents the technical development in locomotive construction
between the years 1854 and 2004. The upper half depicts the
“Taurus”, a high performance locomotive. The lower half depicts
the first functional Alpine locomotive, the Engerth; constructed by
Wilhelm Freiherr von Engerth.
Control car (rail)
Electric multiple unit
Headstock (rolling stock)
List of locomotive builders
List of locomotives
Locomotives in art
Regenerative (dynamic) brakes
World's largest locomotive
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Wikimedia Commons has media related to Locomotives.
An engineer's guide from 1891
Locomotive cutaways and historical locomotives of several countries
ordered by dates
Locomotive Model[permanent dead link]
Locomotive into a Stationary Engine, Popular Science
monthly, February 1919, page 72, Scanned by Google Books:
Short hood / Long hood
Dual Control Stand
AAR wheel arrangement