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In
rail transport Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a prep ...
, track gauge (in
American English American English, sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. English is the most widely spoken language in the United States and in most circumstances ...
, alternatively track gage) is the distance between the two rails of a
railway track A railway track (British English and UIC terminology) or railroad track (American English), also known as permanent way or simply track, is the structure on a railway or railroad consisting of the rails, fasteners, railroad ties (sleepers, ...
. All vehicles on a rail network must have wheelsets that are compatible with the track gauge. Since many different track gauges exist worldwide, gauge differences often present a barrier to wider operation on railway networks. The term derives from the metal bar, or gauge, that is used to ensure the distance between the rails is correct. Railways also deploy two other gauges to ensure compliance with a required standard. A ''
loading gauge A loading gauge is a diagram or physical structure that defines the maximum height and width dimensions in railway vehicles and their loads. Their purpose is to ensure that rail vehicles can pass safely through tunnels and under bridges, and ke ...
'' is a two-dimensional profile that encompasses a cross-section of the track, a rail vehicle and a maximum-sized load: all rail vehicles and their loads must be contained in the corresponding envelope. A ''
structure gauge A structure gauge, also called the minimum clearance outline, is a diagram or physical structure that sets limits to the extent that bridges, tunnels and other infrastructure can encroach on rail vehicles. It specifies the height and width of pl ...
'' specifies the outline into which structures (bridges, platforms, lineside equipment etc.) must not encroach.


Uses of the term

The most common use of the term "track gauge" refers to the transverse distance between the inside surfaces of the two load-bearing rails of a
railway track A railway track (British English and UIC terminology) or railroad track (American English), also known as permanent way or simply track, is the structure on a railway or railroad consisting of the rails, fasteners, railroad ties (sleepers, ...
, usually measured at to below the top of the rail head in order to clear worn corners and allow for rail heads having sloping sides. The term derives from the "gauge", a metal bar with a precisely positioned lug at each end that track crews use to ensure the actual distance between the rails lies within tolerances of a prescribed standard: on curves, for example, the spacing is wider than normal. Deriving from the name of the bar, the distance between these rails is also referred to as the track gauge.


Selection of gauge


Early track gauges

The earliest form of railway was a wooden wagonway, along which single wagons were manhandled, almost always in or from a mine or quarry. Initially the wagons were guided by human muscle power; subsequently by various mechanical methods. Timber rails wore rapidly: later, flat cast-iron plates were provided to limit the wear. In some localities, the plates were made L-shaped, with the vertical part of the L guiding the wheels; this is generally referred to as a "plateway". Flanged wheels eventually became universal, and the spacing between the rails had to be compatible with that of the wagon wheels.M. J. T. Lewis (1970), ''Early Wooden Railways'', Routledge Keegan Paul, London As the guidance of the wagons was improved, short strings of wagons could be connected and pulled by teams of horses, and the track could be extended from the immediate vicinity of the mine or quarry, typically to a navigable waterway. The wagons were built to a consistent pattern and the track would be made to suit the needs of the horses and wagons: the gauge was more critical. The Penydarren Tramroad of 1802 in South Wales, a plateway, spaced these at over the outside of the upstands.R. Cragg (1997), ''Civil Engineering Heritage – Wales and West Central'', Thomas Telford Publishing, London, 2nd edition, England, The Penydarren Tramroad probably carried the first journey by a locomotive, in 1804, and it was successful for the locomotive, but unsuccessful for the track: the plates were not strong enough to carry its weight. A considerable progressive step was made when cast iron edge rails were first employed; these had the major axis of the rail section configured vertically, giving a much stronger section to resist bending forces, and this was further improved when fish-belly rails were introduced.Andy Guy and Jim Rees, ''Early Railways 1569–1830'', Shire Publications in association with the National Railway Museum, Oxford, 2011, Edge rails required a close match between rail spacing and the configuration of the wheelsets, and the importance of the gauge was reinforced. Railways were still seen as local concerns: there was no appreciation of a future connection to other lines, and selection of the track gauge was still a pragmatic decision based on local requirements and prejudices, and probably determined by existing local designs of (road) vehicles. Thus, the
Monkland and Kirkintilloch Railway The Monkland and Kirkintilloch Railway was an early mineral railway running from a colliery at Monklands to the Forth and Clyde Canal at Kirkintilloch, Scotland. It was the first railway to use a rail ferry, the first public railway in Scotla ...
(1826) in the West of Scotland used ;Don Martin, ''The Monkland and Kirkintilloch and Associated Railways'', Strathkelvin Public Libraries, Kirkintilloch, 1995, the
Dundee and Newtyle Railway The Dundee and Newtyle Railway opened in 1831 and was the first railway in the north of Scotland. It was built to carry goods between Dundee and the fertile area known as Strathmore; this involved crossing the Sidlaw Hills, and was accomplish ...
(1831) in the north-east of Scotland adopted ;N. Ferguson (1995), ''The Dundee and Newtyle Railway including the Alyth and Blairgowrie Branches'', The Oakwood Press, . the
Redruth and Chasewater Railway The Redruth and Chasewater Railway, (otherwise called the ''Redruth and Chacewater Railway'' using modern spelling), was an early mineral railway line in Cornwall, England, UK. It opened in 1825 and was built to convey the output from copper mine ...
(1825) in Cornwall chose . The
Arbroath and Forfar Railway The Arbroath and Forfar Railway was a railway that connected Forfar with the port town of Arbroath, in Scotland. It opened in 1838–1839 and it was successful in making an operating profit, but it was always desperately short of capital. It u ...
opened in 1838 with a gauge of ,
Francis Whishaw Francis Whishaw (13 July 1804 – October 1856) was an English civil engineer. He was known for his role in the Society of Arts, and as a writer on railways. Later in life he was a promoter of telegraph companies. Life Francis Whishaw was born 1 ...
, ''The Railways of Great Britain and Ireland Practically Described and Illustrated'', 1842, reprint 1969, David & Charles (Publishers) Limited, Newton Abbot,
and the
Ulster Railway The Ulster Railway was a railway company operating in Ulster, Ireland. The company was incorporated in 1836 and merged with two other railway companies in 1876 to form the Great Northern Railway (Ireland). History The Ulster Railway was a ...
of 1839 used .


Standard gauge appears

Locomotives were being developed in the first decades of the 19th century; they took various forms, but
George Stephenson George Stephenson (9 June 1781 – 12 August 1848) was a British civil engineer and mechanical engineer. Renowned as the "Father of Railways", Stephenson was considered by the Victorians a great example of diligent application and thirst for ...
developed a successful locomotive on the
Killingworth Killingworth, formerly Killingworth Township, is a town in North Tyneside, England. Killingworth was built as a planned town in the 1960s, next to Killingworth Village, which existed for centuries before the Township. Other nearby towns and ...
Wagonway, where he worked. His designs were so successful that they became the standard, and when the
Stockton and Darlington Railway The Stockton and Darlington Railway (S&DR) was a railway company that operated in north-east England from 1825 to 1863. The world's first public railway to use steam locomotives, its first line connected collieries near Shildon with Darli ...
was opened in 1825, it used his locomotives, with the same gauge as the Killingworth line, .W W Tomlinson, ''The North Eastern Railway, its Rise and Development'', Andrew Reid & Co, Newcastle upon Tyne, 1915Nicholas Wood, ''A Practical Treatise on Rail-Roads'', Longman, Orme, Brown, Green and Longmans, London, Third edition, 1838 The Stockton and Darlington line was immensely successful, and when the
Liverpool and Manchester Railway The Liverpool and Manchester Railway (L&MR) was the first inter-city railway in the world. It opened on 15 September 1830 between the Lancashire towns of Liverpool and Manchester in England. It was also the first railway to rely exclusively ...
, the first intercity line, was built (it opened in 1830), it used the same gauge. It was also hugely successful, and the gauge (now eased to ), became the automatic choice: "
standard gauge A standard-gauge railway is a railway with a track gauge of . The standard gauge is also called Stephenson gauge (after George Stephenson), International gauge, UIC gauge, uniform gauge, normal gauge and European gauge in Europe, and SGR in Ea ...
".


Gauge differences

The Liverpool and Manchester was quickly followed by other trunk railways, with the
Grand Junction Railway The Grand Junction Railway (GJR) was an early railway company in the United Kingdom, which existed between 1833 and 1846 when it was amalgamated with other railways to form the London and North Western Railway. The line built by the company w ...
and the
London and Birmingham Railway The London and Birmingham Railway (L&BR) was a railway company in the United Kingdom, in operation from 1833 to 1846, when it became part of the London and North Western Railway (L&NWR). The railway line which the company opened in 1838, betw ...
forming a huge critical mass of
standard gauge A standard-gauge railway is a railway with a track gauge of . The standard gauge is also called Stephenson gauge (after George Stephenson), International gauge, UIC gauge, uniform gauge, normal gauge and European gauge in Europe, and SGR in Ea ...
. When Bristol promoters planned a line from London, they employed the innovative engineer
Isambard Kingdom Brunel Isambard Kingdom Brunel (; 9 April 1806 – 15 September 1859) was a British civil engineer who is considered "one of the most ingenious and prolific figures in engineering history," "one of the 19th-century engineering giants," and "one ...
. He decided on a wider gauge, to give greater stability, and the
Great Western Railway The Great Western Railway (GWR) was a British railway company that linked London with the southwest, west and West Midlands of England and most of Wales. It was founded in 1833, received its enabling Act of Parliament on 31 August 1835 and r ...
adopted a gauge of , later eased to . This became known as ''
broad gauge A broad-gauge railway is a railway with a track gauge (the distance between the rails) broader than the used by standard-gauge railways. Broad gauge of , commonly known as Russian gauge, is the dominant track gauge in former Soviet Union (CIS ...
''. The
Great Western Railway The Great Western Railway (GWR) was a British railway company that linked London with the southwest, west and West Midlands of England and most of Wales. It was founded in 1833, received its enabling Act of Parliament on 31 August 1835 and r ...
(GWR) was successful and was greatly expanded, directly and through friendly associated companies, widening the scope of broad gauge. At the same time, other parts of Britain built railways to standard gauge, and British technology was exported to European countries and parts of North America, also using standard gauge. Britain polarised into two areas: those that used
broad gauge A broad-gauge railway is a railway with a track gauge (the distance between the rails) broader than the used by standard-gauge railways. Broad gauge of , commonly known as Russian gauge, is the dominant track gauge in former Soviet Union (CIS ...
and those that used standard gauge. In this context, standard gauge was referred to as "narrow gauge" to indicate the contrast. Some smaller concerns selected other non-standard gauges: the
Eastern Counties Railway The Eastern Counties Railway (ECR) was an English railway company incorporated in 1836 intended to link London with Ipswich via Colchester, and then extend to Norwich and Yarmouth. Construction began in 1837 on the first nine miles at the Lond ...
adopted . Most of them converted to standard gauge at an early date, but the GWR's broad gauge continued to grow. The larger railway companies wished to expand geographically, and large areas were considered to be under their control. When a new independent line was proposed to open up an unconnected area, the gauge was crucial in determining the allegiance that the line would adopt: if it was broad gauge, it must be friendly to the Great Western railway; if narrow (standard) gauge, it must favour the other companies. The battle to persuade or coerce that choice became very intense, and became referred to as "the gauge wars". As passenger and freight transport between the two areas became increasingly important, the difficulty of moving from one gauge to the other—the ''
break of gauge With railways, a break of gauge occurs where a line of one track gauge (the distance between the rails, or between the wheels of trains designed to run on those rails) meets a line of a different gauge. Trains and rolling stock generally cannot ...
''—became more prominent and more objectionable. In 1845 a
Royal Commission on Railway Gauges The Royal Commission on Railway Gauges was held in the United Kingdom in 1845 to choose between the Broad Gauge of the Great Western Railway and its allies, and the so-called narrow gauge used by most of the rest of the country. The situation in ...
was created to look into the growing problem, and this led to the
Regulating the Gauge of Railways Act 1846 The Railway Regulation (Gauge) Act 1846 (9 & 10 Vic. c.57) is an Act of the Parliament of the United Kingdom, that was designed to standardise railway tracks. It achieved royal assent on 18 August 1846, during the reign of Queen Victoria of ...
, which forbade the construction of broad gauge lines unconnected with the broad gauge network. The broad gauge network was eventually converted—a progressive process completed in 1892, called
gauge conversion Gauge conversion is the changing of one railway track gauge (the distance between the running rails) to another. Sleepers If tracks are converted to a narrower gauge, the existing sleepers (ties) may be used. However, replacement is required i ...
. The same Act mandated the gauge of for use in Ireland.


Gauge selection in other countries

As railways were built in other countries, the gauge selection was pragmatic: the track would have to fit the rolling stock. If locomotives were imported from elsewhere, especially in the early days, the track would be built to fit them. In some cases standard gauge was adopted, but many countries or companies chose a different gauge as their national gauge, either by governmental policy, or as a matter of individual choice.


Terminology

''Standard gauge'' is generally known world-wide as being . Terms such as ''broad gauge'' and ''narrow gauge'' do not have any fixed meaning beyond being materially wider or narrower than standard. In British practice, the space between the rails of a track is colloquially referred to as the "four-foot", and the space between two tracks the "six-foot", descriptions relating to the respective dimensions.


Standard gauge

In modern usage the term "standard gauge" refers to . Standard gauge is dominant in a majority of countries, including those in North America, most of western Europe, North Africa and the Middle east, and in China.


Broad gauge

In modern usage, the term "broad gauge" generally refers to track spaced significantly wider than . Broad gauge is the dominant gauge in countries in Indian subcontinent, the former Soviet Union (CIS states, Baltic states, Georgia and Ukraine), Mongolia and Finland, Spain, Portugal, Argentina, Chile and Ireland. It is also use for the suburban railway systems in
South Australia South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories ...
, and
Victoria Victoria most commonly refers to: * Victoria (Australia), a state of the Commonwealth of Australia * Victoria, British Columbia, provincial capital of British Columbia, Canada * Victoria (mythology), Roman goddess of Victory * Victoria, Seyche ...
, Australia.


Medium gauge

The term "medium gauge" had different meanings throughout history, depending on the local dominant gauge in use. In 1840s, the
Irish gauge Railways with a track gauge of fall within the category of broad gauge railways. , they were extant in Australia, Brazil and Ireland. History 600 BC :The Diolkos (Δίολκος) across the Isthmus of Corinth in Greece – a grooved paved ...
was considered a medium gauge compared to Brunel's
broad gauge A broad-gauge railway is a railway with a track gauge (the distance between the rails) broader than the used by standard-gauge railways. Broad gauge of , commonly known as Russian gauge, is the dominant track gauge in former Soviet Union (CIS ...
and the narrow gauge, nowadays being
standard gauge A standard-gauge railway is a railway with a track gauge of . The standard gauge is also called Stephenson gauge (after George Stephenson), International gauge, UIC gauge, uniform gauge, normal gauge and European gauge in Europe, and SGR in Ea ...
.


Narrow gauge

In modern usage, the term "narrow gauge" generally refers to track spaced significantly narrower than . Narrow gauge is the dominant or second dominant gauge in countries of Southern, Central Africa, East Africa, Southeast Asia, Japan, Taiwan, Philippines, Central America and South America, During the period known as " the Battle of the gauges", Stephenson's standard gauge was commonly known as "narrow gauge", while Brunel's railway's gauge was termed "
broad gauge A broad-gauge railway is a railway with a track gauge (the distance between the rails) broader than the used by standard-gauge railways. Broad gauge of , commonly known as Russian gauge, is the dominant track gauge in former Soviet Union (CIS ...
". Many narrow gauge railways were built in mountainous regions such as
Wales Wales ( cy, Cymru ) is a country that is part of the United Kingdom. It is bordered by England to the east, the Irish Sea to the north and west, the Celtic Sea to the south west and the Bristol Channel to the south. It had a population in 2 ...
, the
Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
of North America, Central Europe and South America.
Industrial railway An industrial railway is a type of railway (usually private) that is not available for public transportation and is used exclusively to serve a particular industrial, logistics, or military site. In regions of the world influenced by British ra ...
s and
mine railway A mine railway (or mine railroad, U.S.), sometimes pit railway, is a railway constructed to carry materials and workers in and out of a mine. Materials transported typically include ore, coal and overburden (also called variously spoils, waste, ...
s across the world are often narrow gauge. Sugar cane and banana plantations are mostly served by narrow gauges.


Minimum-gauge

Very narrow gauges of under were used for some
industrial railway An industrial railway is a type of railway (usually private) that is not available for public transportation and is used exclusively to serve a particular industrial, logistics, or military site. In regions of the world influenced by British ra ...
s in space-restricted environments such as mines or farms. The French company
Decauville Decauville () was a manufacturing company which was founded by Paul Decauville (1846–1922), a French pioneer in industrial railways. Decauville's major innovation was the use of ready-made sections of light, narrow gauge track fastened to st ...
developed and tracks, mainly for mines; Heywood developed gauge for estate railways. The most common minimum-gauges were , , , , or .


Break of gauge

Through operation between railway networks with different gauges was originally impossible; goods had to be transshipped and passengers had to change trains. This was obviously a major obstacle to convenient transport, and in Great Britain, led to political intervention. On narrow gauge lines,
Rollbock ''Rollbocks'', sometimes called transporter trailers, are narrow gauge railway trucks or bogies that allow a standard gauge wagon to 'piggyback' on a narrow-gauge line. The Vevey system enables a coupled train of standard gauge wagons to be auto ...
s or
transporter wagon A transporter wagon, in railway terminology, is a wagon ( UIC) or railroad car (US) designed to carry other railway equipment. Normally, it is used to transport equipment of a different rail gauge. In most cases, a transporter wagon is a na ...
s are used: standard gauge wagons are carried on narrow gauge lines on these special vehicles, generally with rails of the wider gauge to enable those vehicles to roll on and off at transfer points. On the Transmongolian Railway, Russia and Mongolia use while China uses the standard gauge of 1,435 mm. At the border, each carriage is lifted and its bogies are changed. The operation can take several hours for a whole train of many carriages. Other examples include crossings into or out of the former Soviet Union: Ukraine/Slovakia border on the Bratislava–L'viv train, and the Romania/Moldova border on the Chișinău-Bucharest train. A system developed by
Talgo Talgo (officially Patentes Talgo, SAU) is a Spanish manufacturer of intercity, standard, and high-speed passenger trains. Corporate history TALGO, an abbreviation of Tren Articulado Ligero Goicoechea Oriol (English: ''Lightweight articulated tra ...
and
Construcciones y Auxiliar de Ferrocarriles Construcciones y Auxiliar de Ferrocarriles (Grupo CAF, literally "Construction and Other Railway Services") is a Spanish publicly listed company which manufactures railway vehicles and equipment and buses through its Solaris Bus & Coach subsidi ...
(CAF) of Spain uses variable gauge wheelsets; at the border between France and Spain, through passenger trains are drawn slowly through apparatus that alters the gauge of the wheels, which slide laterally on the axles.Alberto García Álvarez, ''Automatic Gauge Changeover for Trains in Spain'', Fundación de los Ferrocarrilos Españoles, 2010, online a

/ref> A similar system is used between China and Central Asia, and between Poland and Ukraine, using the
SUW 2000 SUW 2000 is a Polish variable gauge system that allows trains to cross a break of gauge. It is interoperable with the German Rafil Type V system (built by the Radsatzfabrik Ilsenburg). History The SUW 2000 system was designed by Ryszard Suwalski. ...
and INTERGAUGE variable axle systems. China and Poland use standard gauge, while Central Asia and Ukraine use .


Dual gauge

When individual railway companies have chosen different gauges and have needed to share a route where space on the ground is limited, mixed gauge (or dual gauge) track, in which three (sometimes four) rails are supported in the same track structure, can be necessary. The most frequent need for such track was at the approaches to city terminals or at
break-of-gauge With railways, a break of gauge occurs where a line of one track gauge (the distance between the rails, or between the wheels of trains designed to run on those rails) meets a line of a different gauge. Trains and rolling stock generally cannot ...
stations. Tracks of multiple gauges involve considerable costs in construction (including signalling work) and complexities in track maintenance, and may require some speed restrictions. They are therefore built only when absolutely necessary. If the difference between the two gauges is large enough – for example between and – three-rail dual-gauge is possible, but if not – for example between and – four rails must be used. Dual-gauge rail lines occur (or have occurred) in Argentina, Australia, Brazil, Japan, North Korea, Spain, Switzerland, Tunisia and Vietnam. On the GWR, there was an extended period between political intervention in 1846 that prevented major expansion of its
broad gauge A broad-gauge railway is a railway with a track gauge (the distance between the rails) broader than the used by standard-gauge railways. Broad gauge of , commonly known as Russian gauge, is the dominant track gauge in former Soviet Union (CIS ...
The Act of Parliament did not prohibit expansion of the existing broad gauge system, but it had the indirect and delayed effect of forcing conformity with the "standard" gauge eventually. and the final
gauge conversion Gauge conversion is the changing of one railway track gauge (the distance between the running rails) to another. Sleepers If tracks are converted to a narrower gauge, the existing sleepers (ties) may be used. However, replacement is required i ...
to standard gauge in 1892. During this period, many locations practicality required mixed gauge operation, and in station areas the track configuration was extremely complex. This was compounded by the common rail having to be at the platform side in stations; therefore, in many cases, standard-gauge trains needed to be switched from one side of the track to the other at the approach. A special fixed point arrangement was devised for the purpose, where the track layout was simple enough.S.C. Jenkins and R.C. Langley, ''The West Cornwall Railway'', The Oakwood Press, Usk, 2002, ISBN 0853615896, gives an illustration and description on page 66. In some cases, mixed gauge trains were operated with wagons of both gauges. For example, MacDermotE T MacDermot, ''History of the Great Western Railway'', vol II: 1863–1921, published by the Great Western Railway, London, 1931, p. 316 wrote:
In November 1871 a novelty in the shape of a ''mixed-gauge'' goods train was introduced between Truro and Penzance. It was worked by a narrow-gauge engine, and behind the narrow-gauge trucks came a broad-gauge match-truck with wide buffers and sliding shackles, followed by the broad-gauge trucks. Such trains continued to run in West Cornwall until the abolition of the Broad Gauge; they had to stop or come down to walking pace at all stations where fixed points existed and the narrow portion side-stepped to right or left.


Nominal track gauge

The nominal track gauge is the distance between the inner faces of the rails. In current practice, it is specified at a certain distance below the rail head as the inner faces of the rail head (the ''gauge faces'') are not necessarily vertical. Some amount of tolerance is necessarily allowed from the nominal gauge to allow for wear, etc.; this tolerance is typically greater for track limited to slower speeds, and tighter for track where higher speeds are expected (as an example, in the US the gauge is allowed to vary between to for track limited to , while track is allowed only to . Given the allowed tolerance, it is a common practice to widen the gauge slightly in curves, particularly those of shorter radius (which are inherently slower speed curves). Rolling stock on the network must have running gear ( wheelsets) that are compatible with the gauge, and therefore the gauge is a key parameter in determining interoperability, but there are many others – see below. In some cases in the earliest days of railways, the railway company saw itself as an infrastructure provider only, and independent hauliers provided wagons suited to the gauge. Colloquially the wagons might be referred to as "four-foot gauge wagons", say, if the track had a gauge of four feet. This nominal value does not equate to the flange spacing, as some freedom is allowed for. An infrastructure manager might specify new or replacement track components at a slight variation from the nominal gauge for pragmatic reasons.


Units

The gauge is defined in
Imperial unit The imperial system of units, imperial system or imperial units (also known as British Imperial or Exchequer Standards of 1826) is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed thr ...
s,
metric unit The metric system is a system of measurement that succeeded the decimalised system based on the metre that had been introduced in France in the 1790s. The historical development of these systems culminated in the definition of the Internati ...
s or SI units. Imperial units were established in the United Kingdom by ''The Weights and Measures Act of 1824''. The
United States customary units United States customary units form a system of measurement units commonly used in the United States and U.S. territories since being standardized and adopted in 1832. The United States customary system (USCS or USC) developed from English unit ...
for length did not agree with the Imperial system until 1959, when one
international yard The international yard and pound are two units of measurement that were the subject of an agreement among representatives of six nations signed on 1 July 1959: the United States, United Kingdom, Canada, Australia, New Zealand, and South Africa. ...
was defined as 0.9144 meters and, as derived units, 1 foot (= yd) as 0.3048 meter and 1 inch (= yd) as 25.4 mm. The list shows the Imperial and other units that have been used for track gauge definitions:


Temporary way – permanent way

A temporary way is the temporary track often used for construction, to be replaced by the
permanent way A railway track (British English and UIC terminology) or railroad track (American English), also known as permanent way or simply track, is the structure on a railway or railroad consisting of the rails, fasteners, railroad ties (sleepers ...
(the structure consisting of the rails, fasteners, sleepers/ties and
ballast Ballast is material that is used to provide stability to a vehicle or structure. Ballast, other than cargo, may be placed in a vehicle, often a ship or the gondola of a balloon or airship, to provide stability. A compartment within a boat, ship ...
(or slab track), plus the underlying subgrade) when construction nears completion. In many cases narrow-gauge track is used for a temporary way because of the convenience in laying it and changing its location over unimproved ground. In restricted spaces such as tunnels, the temporary way might be double track even though the tunnel will ultimately be single track. The
Airport Rail Link An airport rail link is a service providing passenger rail transport from an airport to a nearby city by mainline or commuter trains, rapid transit, people mover, or light rail. Direct links operate straight to the airport terminal, while o ...
in Sydney had construction trains of gauge, which were replaced by permanent tracks of gauge. During World War I trench warfare led to a relatively static disposition of infantry, requiring considerable logistics to bring them support staff and supplies (food, ammunition, earthworks materials, etc.). Dense light railway networks using temporary narrow gauge track sections were established by both sides for this purpose.Christian Wolmar, ''Engines of War: How Wars Were Won & Lost on the Railways'', Atlantic Books, London, 2010, In 1939 it was proposed to construct the western section of the Yunnan–Burma Railway using a gauge of , since such tiny or "toy" gauge facilitates the tightest of curves in difficult terrain.


Maintenance standards

Infrastructure owners specify permitted variances from the nominal gauge, and the required interventions when non-compliant gauge is detected. For example, the
Federal Railroad Administration The Federal Railroad Administration (FRA) is an agency in the United States Department of Transportation (DOT). The agency was created by the Department of Transportation Act of 1966. The purpose of the FRA is to promulgate and enforce rail saf ...
in the USA specifies that the actual gauge of a 1,435 mm track that is rated for a maximum of must be between and .


Advantages and disadvantages of different track gauges

Speed, capacity, and economy are generally objectives of rail transport, but there is often an inverse relationship between these priorities. There is a common misconception that a narrower gauge permits a tighter turning radius, but for practical purposes, there is no meaningful relationship between gauge and curvature.


Construction cost

Narrower gauge railways usually cost less to build because they are usually lighter in construction, using smaller
cars A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarded as t ...
and
locomotive 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 a multiple unit, motor coach, railcar or power car; the us ...
s (smaller
loading gauge A loading gauge is a diagram or physical structure that defines the maximum height and width dimensions in railway vehicles and their loads. Their purpose is to ensure that rail vehicles can pass safely through tunnels and under bridges, and ke ...
), as well as smaller bridges, smaller
tunnel A tunnel is an underground passageway, dug through surrounding soil, earth or rock, and enclosed except for the entrance and exit, commonly at each end. A pipeline is not a tunnel, though some recent tunnels have used immersed tube const ...
s (smaller
structure gauge A structure gauge, also called the minimum clearance outline, is a diagram or physical structure that sets limits to the extent that bridges, tunnels and other infrastructure can encroach on rail vehicles. It specifies the height and width of pl ...
). Narrow gauge is thus often used in mountainous terrain, where the savings in civil engineering work can be substantial. It is also used in sparsely populated areas, with low potential demand, and for temporary railways that will be removed after short-term use, such as for construction, the logging industry, the mining industry, or large-scale construction projects, especially in confined spaces (see Temporary way – permanent way). For temporary railways which will be removed after short-term use, such as those used in logging, mining or large-scale construction projects (especially in confined spaces, such as when constructing the
Channel Tunnel The Channel Tunnel (french: Tunnel sous la Manche), also known as the Chunnel, is a railway tunnel that connects Folkestone (Kent, England, UK) with Coquelles ( Hauts-de-France, France) beneath the English Channel at the Strait of Dover. ...
), a narrow-gauge railway is substantially cheaper and easier to install and remove. Such railways have almost vanished, however, due to the capabilities of modern
truck A truck or lorry is a motor vehicle designed to transport cargo, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame constructi ...
s. In many countries, narrow-gauge railways were built as branch lines to feed traffic to standard-gauge lines due to lower construction costs. The choice was often not between a narrow- and standard-gauge railway, but between a narrow-gauge railway and none at all. Broader gauge railways are generally more expensive to build, because they are usually heavier in construction, use larger
cars A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarded as t ...
and
locomotive 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 a multiple unit, motor coach, railcar or power car; the us ...
s (larger
loading gauge A loading gauge is a diagram or physical structure that defines the maximum height and width dimensions in railway vehicles and their loads. Their purpose is to ensure that rail vehicles can pass safely through tunnels and under bridges, and ke ...
), as well as larger bridges, larger
tunnel A tunnel is an underground passageway, dug through surrounding soil, earth or rock, and enclosed except for the entrance and exit, commonly at each end. A pipeline is not a tunnel, though some recent tunnels have used immersed tube const ...
s (larger
structure gauge A structure gauge, also called the minimum clearance outline, is a diagram or physical structure that sets limits to the extent that bridges, tunnels and other infrastructure can encroach on rail vehicles. It specifies the height and width of pl ...
). But broader gauges offer higher speed and capacity. For routes with high traffic, greater capacity may more than offset the higher initial cost of construction.


Interchangeability

The
value Value or values may refer to: Ethics and social * Value (ethics) wherein said concept may be construed as treating actions themselves as abstract objects, associating value to them ** Values (Western philosophy) expands the notion of value beyo ...
or
utility As a topic of economics, utility is used to model worth or value. Its usage has evolved significantly over time. The term was introduced initially as a measure of pleasure or happiness as part of the theory of utilitarianism by moral philosophe ...
a user derives from a
good In most contexts, the concept of good denotes the conduct that should be preferred when posed with a choice between possible actions. Good is generally considered to be the opposite of evil and is of interest in the study of ethics, morality, ph ...
or
service Service may refer to: Activities * Administrative service, a required part of the workload of university faculty * Civil service, the body of employees of a government * Community service, volunteer service for the benefit of a community or a p ...
depends on the number of users of compatible products – the "
network effect In economics, a network effect (also called network externality or demand-side economies of scale) is the phenomenon by which the value or utility a user derives from a good or service depends on the number of users of compatible products. Ne ...
" in economics. Network effects are typically positive, resulting in a given user deriving more value from a product as other users join the same network. At national levels, the network effect has resulted in commerce extending beyond regional and national boundaries. Increasingly, many governments and companies have made their railways' engineering and operational standards compatible in order to achieve interchangeability – hence faster, longer-distance train operation. A major barrier to achieving interchangeability, however, is
path dependence Path dependence is a concept in economics and the social sciences, referring to processes where past events or decisions constrain later events or decisions. It can be used to refer to outcomes at a single point in time or to long-run equilibria ...
– in this context the persistence of an already adopted standard to which equipment, infrastructure and training has become aligned. Since adopting a new standard is difficult and expensive, continuing with an existing standard can remain attractive unless longer-term benefits are given appropriate weight. An example of the consequences of path dependence is the persistence in the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and Nor ...
– the earliest nation to develop and adopt railway technologies – of
structure gauge A structure gauge, also called the minimum clearance outline, is a diagram or physical structure that sets limits to the extent that bridges, tunnels and other infrastructure can encroach on rail vehicles. It specifies the height and width of pl ...
s that are too small to allow the larger
rolling stock The term rolling stock in the rail transport industry refers to railway vehicles, including both powered and unpowered vehicles: for example, locomotives, freight and passenger cars (or coaches), and non-revenue cars. Passenger vehicles can b ...
of continental Europe to operate in that country. The reduced cost, greater efficiency, and greater economic opportunity offered by the use of a common standard has resulted in the historical multitude of track gauges dwindling to a small number that predominate worldwide. When interchangeability has not been achieved, freight and passengers must be transferred through time-consuming procedures requiring manual labour and substantial capital expenditure. Some bulk commodities, such as
coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dead ...
,
ore Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 April ...
, and
gravel Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone. Gravel is classifi ...
, can be mechanically transshipped, but even this is time-consuming, and the equipment required for the transfer is often complex to maintain. Further, if rail lines of different gauges coexist in a network and a
break of gauge With railways, a break of gauge occurs where a line of one track gauge (the distance between the rails, or between the wheels of trains designed to run on those rails) meets a line of a different gauge. Trains and rolling stock generally cannot ...
exists, it is difficult in times of peak demand to move rolling stock to where it is needed. Sufficient rolling stock must be available to meet a narrow-gauge railway's peak demand (which might be greater in comparison to a broader-gauge network), and the surplus equipment generates no cash flow during periods of low demand. In regions where narrow-gauge lines form a small part of the rail network (as was the case on Russia's
Sakhalin Railway Sakhalin Railway (russian: Сахалинская железная дорога) is one of the railway division under Far Eastern Railway that primarily serves in Sakhalin Island. Due to its island location, the railway becomes the second isolate ...
), extra cost is involved in designing, manufacturing or importing narrow-gauge equipment. Solutions to interchangeability problems include
bogie exchange Bogie exchange is a system for operating railway wagons on two or more gauges to overcome difference in the track gauge. To perform a bogie exchange, a car is converted from one gauge to another by removing the bogies or trucks (the chassis co ...
s, a
rollbock ''Rollbocks'', sometimes called transporter trailers, are narrow gauge railway trucks or bogies that allow a standard gauge wagon to 'piggyback' on a narrow-gauge line. The Vevey system enables a coupled train of standard gauge wagons to be auto ...
system,
dual gauge In railway engineering, "gauge" is the transverse distance between the inner surfaces of the heads of two rails, which for the vast majority of railway lines is the number of rails in place. However, it is sometimes necessary for track to c ...
,
variable gauge A variable gauge system allows railway vehicles in a train to travel across a break of gauge between two railway networks with different track gauges. For through operation, a train must be equipped with special bogies holding variable gauge whe ...
, or
gauge conversion Gauge conversion is the changing of one railway track gauge (the distance between the running rails) to another. Sleepers If tracks are converted to a narrower gauge, the existing sleepers (ties) may be used. However, replacement is required i ...
.


Dominant railway gauges

More than half of the world's railways are built to . New railways have been built in Africa to standard gauge. Most of the narrow-gauge railways in India are being converted to the dominant, broad-gauge.


Prevalence

Total for each group of gauges in 2020:


Future

Further convergence of rail gauge use seems likely, as countries seek to build inter-operable networks, and international organisations seek to build macro-regional and continental networks. Almost all new
high-speed rail High-speed rail (HSR) is a type of rail system that runs significantly faster than traditional rail, using an integrated system of specialised rolling stock and dedicated tracks. While there is no single standard that applies worldwide, lines ...
lines are built to standard gauge, except in Uzbekistan and Russia.


Europe

The
European Union The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been ...
has set out to develop inter-operable freight and passenger rail networks across its area, and is seeking to standardise gauge, signalling and electrical power systems. EU funds have been dedicated to assist
Lithuania Lithuania (; lt, Lietuva ), officially the Republic of Lithuania ( lt, Lietuvos Respublika, links=no ), is a country in the Baltic region of Europe. It is one of three Baltic states and lies on the eastern shore of the Baltic Sea. Lithuania ...
,
Latvia Latvia ( or ; lv, Latvija ; ltg, Latveja; liv, Leţmō), officially the Republic of Latvia ( lv, Latvijas Republika, links=no, ltg, Latvejas Republika, links=no, liv, Leţmō Vabāmō, links=no), is a country in the Baltic region of ...
, and
Estonia Estonia, formally the Republic of Estonia, is a country by the Baltic Sea in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the sea across from Sweden, to the south by Latvia, and ...
in the building of some key railway lines (
Rail Baltica Rail Baltica (also known as Rail Baltic in Estonia) is a high-speed railway under construction between Warsaw, Poland and Tallinn, Estonia, with further connections to Finland via Baltic Sea cruiseferries or the proposed Helsinki–Tallinn Tunn ...
) of
standard gauge A standard-gauge railway is a railway with a track gauge of . The standard gauge is also called Stephenson gauge (after George Stephenson), International gauge, UIC gauge, uniform gauge, normal gauge and European gauge in Europe, and SGR in Ea ...
, and to assist Spain and Portugal in the construction of high-speed lines to connect Iberian cities to one another and to the French high-speed lines. The EU has developed plans for improved freight rail links between Spain, Portugal, and the rest of Europe.


Trans-Asian Railway

The
United Nations The United Nations (UN) is an intergovernmental organization whose stated purposes are to maintain international peace and security, develop friendly relations among nations, achieve international cooperation, and be a centre for harmonizi ...
Economic and Social Commission for Asia and the Pacific The United Nations Economic and Social Commission for Asia and the Pacific (ESCAP) is one of the five regional commissions under the jurisdiction of the United Nations Economic and Social Council. It was established in order to increase economic ...
(UNESCAP) is planning a Trans-Asian Railway that will link Europe and the Pacific, with a Northern Corridor from Europe to the Korean Peninsula, a Southern Corridor from Europe to Southeast Asia, and a North–South corridor from Northern Europe to the Persian Gulf. All these would encounter breaks of gauge as they cross Asia. Current plans have mechanized facilities at the breaks of gauge to move
containers A container is any receptacle or enclosure for holding a product used in storage, packaging, and transportation, including shipping. Things kept inside of a container are protected on several sides by being inside of its structure. The term ...
from train to train rather than widespread gauge conversion. The Northern Corridor through Russia already operates since before year 2000, with increasing volumes China–Europe.


The Americas

* 2008: Proposed link between
Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in t ...
and Colombia * 2008: Venezuela via Brazil to Argentina –
standard gauge A standard-gauge railway is a railway with a track gauge of . The standard gauge is also called Stephenson gauge (after George Stephenson), International gauge, UIC gauge, uniform gauge, normal gauge and European gauge in Europe, and SGR in Ea ...
* 2008: A proposed
metre gauge Metre-gauge railways are narrow-gauge railways with track gauge of or 1 metre. The metre gauge is used in around of tracks around the world. It was used by European colonial powers, such as the French, British and German Empires. In Europe, la ...
line across Southern
Paraguay Paraguay (; ), officially the Republic of Paraguay ( es, República del Paraguay, links=no; gn, Tavakuairetã Paraguái, links=si), is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to ...
to link Argentina at Resistencia to Brazil at
Cascavel Cascavel is a municipality in the state of Paraná in Brazil. It is the fifth most populous city in the state with 332,333 residents, according to IBGE, a government agency. The distance to Curitiba, the state capital, is 491 kilometers by fr ...
; both those lines are , and the new line would allow "bioceanic" running from the Atlantic port of
Paranaguá Paranaguá (''Great Round Sea'', in Tupi) is a city in the state of Paraná in Brazil. Founded in 1648, it is Paraná's oldest city. It is known for the Port of Paranaguá, which serves as both the sea link for Curitiba, to the west and the ca ...
in Brazil to that of
Antofagasta Antofagasta () is a port city in northern Chile, about north of Santiago. It is the capital of Antofagasta Province and Antofagasta Region. According to the 2015 census, the city has a population of 402,669. After the Spanish American war ...
in
Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
on the Pacific.


Africa

The East African Railway Master Plan is a proposal for rebuilding and expanding railway lines connecting
Ethiopia Ethiopia, , om, Itiyoophiyaa, so, Itoobiya, ti, ኢትዮጵያ, Ítiyop'iya, aa, Itiyoppiya officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the no ...
,
Djibouti Djibouti, ar, جيبوتي ', french: link=no, Djibouti, so, Jabuuti officially the Republic of Djibouti, is a country in the Horn of Africa, bordered by Somalia to the south, Ethiopia to the southwest, Eritrea in the north, and the Red S ...
,
Kenya ) , national_anthem = " Ee Mungu Nguvu Yetu"() , image_map = , map_caption = , image_map2 = , capital = Nairobi , coordinates = , largest_city = Nairobi ...
,
Uganda }), is a landlocked country in East Africa. The country is bordered to the east by Kenya, to the north by South Sudan, to the west by the Democratic Republic of the Congo, to the south-west by Rwanda, and to the south by Tanzania. The souther ...
,
Rwanda Rwanda (; rw, u Rwanda ), officially the Republic of Rwanda, is a landlocked country in the Great Rift Valley of Central Africa, where the African Great Lakes region and Southeast Africa converge. Located a few degrees south of the Equat ...
,
Burundi Burundi (, ), officially the Republic of Burundi ( rn, Repuburika y’Uburundi ; Swahili: ''Jamuhuri ya Burundi''; French: ''République du Burundi'' ), is a landlocked country in the Great Rift Valley at the junction between the African Gr ...
,
Tanzania Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands and ...
,
South Sudan South Sudan (; din, Paguot Thudän), officially the Republic of South Sudan ( din, Paankɔc Cuëny Thudän), is a landlocked country in East Africa. It is bordered by Ethiopia, Sudan, Central African Republic, Democratic Republic of the Con ...
and beyond. The plan is managed by infrastructure ministers from participating
East African Community The East African Community (EAC) is an intergovernmental organisation composed of seven countries in the Great Lakes region of East Africa: the Democratic Republic of the Congo, the United Republic of Tanzania, the Republics of Kenya, Burundi, ...
countries in association with transport consultation firm CPCS Transcom. Older railways are of or gauge. Newly rebuilt lines will use
standard gauge A standard-gauge railway is a railway with a track gauge of . The standard gauge is also called Stephenson gauge (after George Stephenson), International gauge, UIC gauge, uniform gauge, normal gauge and European gauge in Europe, and SGR in Ea ...
. Regular freight and passenger services began on the standard gauge Mombasa–Nairobi railway in 2017 and on the standard gauge Addis Ababa–Djibouti railway in 2018. Lines for iron ore to
Kribi Kribi is a beach resort and sea port in Cameroon. Location The coastal town of Kribi lies on the Gulf of Guinea, in Océan Department, South Province, at the mouth of the Kienké River. This location, lies approximately , by road, south of ...
in Cameroon are likely to be with a likely connection to the same port from the Cameroon system. Nigeria's railways are mostly Cape gauge. The Lagos–Kano Standard Gauge Railway is a
gauge conversion Gauge conversion is the changing of one railway track gauge (the distance between the running rails) to another. Sleepers If tracks are converted to a narrower gauge, the existing sleepers (ties) may be used. However, replacement is required i ...
project by the Nigerian Government to create a north–south standard gauge rail link. The first converted segment, between Abuja and
Kaduna Kaduna is the capital city of Kaduna State, and the former political capital of Northern Nigeria. It is located in north-western Nigeria, on the Kaduna River. It is a trade Centre and a major transportation hub as the gateway to northern Niger ...
, was completed in July 2016. The
African Union The African Union (AU) is a continental union consisting of 55 member states located on the continent of Africa. The AU was announced in the Sirte Declaration in Sirte, Libya, on 9 September 1999, calling for the establishment of the Africa ...
has a 50-year plan to connect the capital cities and major centres by high-speed railways.


Timeline


See also

*
List of track gauges This list presents an overview of railway track gauges by size. A gauge is measured between the inner faces of the rails. Track gauges by size Minimum and ridable miniature railways For ridable miniature railways and minimum gauge railways, t ...
*
Rapid transit track gauge The vast majority of rapid transit systems use . Some of the largest and oldest subway systems in the world use standard gauge in agreement with the country wide dominant usage for track gauge, e.g. London Underground (1863), Chicago "L" (1892), ...
*
List of tram systems by gauge and electrification The following is a list of tram/streetcar (including heritage trams/heritage streetcars), or light rail systems with their track length, track gauge, electrification system. The vast majority of tram systems use . Generally, standard gauge ...
*
Loading gauge A loading gauge is a diagram or physical structure that defines the maximum height and width dimensions in railway vehicles and their loads. Their purpose is to ensure that rail vehicles can pass safely through tunnels and under bridges, and ke ...
*
Minimum railway curve radius The minimum railway curve radius is the shortest allowable design radius for the centerline of railway tracks under a particular set of conditions. It has an important bearing on construction costs and operating costs and, in combination with ...
*
Overhead line An overhead line or overhead wire is an electrical cable that is used to transmit electrical energy to electric locomotives, trolleybuses or trams. It is known variously as: * Overhead catenary * Overhead contact system (OCS) * Overhead equipment ...
* Rail profile *
Rail terminology Rail or rails may refer to: Rail transport *Rail transport and related matters * Rail (rail transport) or railway lines, the running surface of a railway Arts and media Film * ''Rails'' (film), a 1929 Italian film by Mario Camerini * ''Rail'' ...
*
Rail transport modelling scales Rail transport modelling uses a variety of scales (ratio between the real world and the model) to ensure scale models look correct when placed next to each other. Model railway scales are standardized worldwide by many organizations and hobbyist ...
*
Railway coupling A coupling (or a coupler) is a mechanism typically placed at each end of a railway vehicle that connects them together to form a train. A variety of coupler types have been developed over the course of railway history. Key issues in their desig ...
*
Structure gauge A structure gauge, also called the minimum clearance outline, is a diagram or physical structure that sets limits to the extent that bridges, tunnels and other infrastructure can encroach on rail vehicles. It specifies the height and width of pl ...
*
Third rail A third rail, also known as a live rail, electric rail or conductor rail, is a method of providing electric power to a railway locomotive or train, through a semi-continuous rigid conductor placed alongside or between the rails of a railway t ...
*
Track gauge conversion Gauge conversion is the changing of one railway track gauge (the distance between the running rails) to another. Sleepers If tracks are converted to a narrower gauge, the existing sleepers (ties) may be used. However, replacement is required if ...


Notes


References


External links


OpenRailwayMap
A global track gauge map
A history of track gauge
by George W. Hilton * – A list of railway gauges used or being used worldwide, including gauges that are obsolete.
European Railway Agency: 1520 mm systems
(issues with the participation of 1520/1524 mm gauge countries in the EU rail network)



{{DEFAULTSORT:Rail Gauge Gague