Track gauge
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rail transport Rail transport (also known as train transport) is a means of transport using wheeled vehicles running in railway track, tracks, which usually consist of two parallel steel railway track, rails. Rail transport is one of the two primary means of ...
, track gauge is the distance between the two rails of a
railway track Railway track ( and UIC terminology) or railroad track (), also known as permanent way () or "P way" ( and Indian English), is the structure on a railway or railroad consisting of the rails, fasteners, sleepers ( railroad ties in American ...
. 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 k ...
'' 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'' 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 Railway track ( and UIC terminology) or railroad track (), also known as permanent way () or "P way" ( and Indian English), is the structure on a railway or railroad consisting of the rails, fasteners, sleepers ( railroad ties in American ...
, 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.


Choice 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 the choice of 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 (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 (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 (1825) in Cornwall chose . The Arbroath and Forfar Railway opened in 1838 with a gauge of , Francis Whishaw, ''The Railways of Great Britain and Ireland Practically Described and Illustrated'', 1842, reprint 1969, David & Charles (Publishers) Limited, Newton Abbot, and the Ulster Railway 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 an English civil engineer and Mechanical engineering, mechanical engineer during the Industrial Revolution. Renowned as the "Father of Railways", Stephenson was considered by the Victoria ...
developed a successful locomotive on the Killingworth Wagonway, where he worked. His designs were successful, 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 coal mining, collieries near with ...
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 very 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 Opening of the Liverpool and Manchester Railway, opened on 15 September 1830 between the Lancashire towns of Liverpool and Manchester in England. It ...
, the first intercity line, was opened in 1830, it used the same gauge. It too was very successful, and the gauge, widened to and named "
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 in Europe, and SGR in East Africa. It is the ...
", was well on its way to becoming the established norm.


Gauge differences

The Liverpool and Manchester was quickly followed by other trunk railways, with the Grand Junction Railway and the London and Birmingham Railway forming a huge preponderance 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 in Europe, and SGR in East Africa. It is the ...
. 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 an English civil engineer and mechanical engineer who is considered "one of the most ingenious and prolific figures in engineering history", "one of the 19th-century engi ...
. He decided on a wider gauge, to give greater stability, and the
Great Western Railway The Great Western Railway (GWR) was a History of rail transport in Great Britain, British railway company that linked London with the southwest, west and West Midlands (region), West Midlands of England and most of Wales. It was founded in 1833, ...
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 , more known as Russian gauge, is the dominant track gauge in former Soviet Union countries ...
''. The
Great Western Railway The Great Western Railway (GWR) was a History of rail transport in Great Britain, British railway company that linked London with the southwest, west and West Midlands (region), West Midlands of England and most of Wales. It was founded in 1833, ...
(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 , more known as Russian gauge, is the dominant track gauge in former Soviet Union countries ...
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 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''—became more prominent and more objectionable. In 1845 a Royal Commission on Railway Gauges was created to look into the growing problem, and this led to the Regulating the Gauge of Railways Act 1846, 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. 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, the Middle East, and 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, Finland (which still uses the original Soviet Gauge of 1524mm), Spain, Portugal, Argentina, Chile and Ireland. It is also used for the suburban railway systems in
South Australia South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. With a total land area of , it is the fourth-largest of Australia's states and territories by area, which in ...
, and Victoria,
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
.


Medium gauge

The term "medium gauge" had different meanings throughout history, depending on the local dominant gauge in use. In 1840s, the Irish gauge 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 , more known as Russian gauge, is the dominant track gauge in former Soviet Union countries ...
and the narrow gauge, which became the modern
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 in Europe, and SGR in East Africa. It is the ...
.


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 , more known as Russian gauge, is the dominant track gauge in former Soviet Union countries ...
". Many narrow gauge railways were built in mountainous regions such as
Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...
, 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 great-circle distance, straight-line distance from the northernmost part of Western Can ...
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 r ...
s and mine railways 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 r ...
s in space-restricted environments such as mines or farms. The French company Decauville 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, rollbocks or
transporter wagon A transporter wagon, in railway terminology, is a goods wagon, wagon (International Union of Railways, UIC) or railroad car (US) designed to carry other railway equipment. Normally, it is used to transport equipment of a different rail gauge. ...
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
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Lviv Lviv ( or ; ; ; see #Names and symbols, below for other names) is the largest city in western Ukraine, as well as the List of cities in Ukraine, fifth-largest city in Ukraine, with a population of It serves as the administrative centre of ...
train, and the Romania/Moldova border on the
Chișinău Chișinău ( , , ; formerly known as Kishinev) is the Capital city, capital and List of cities and towns in Moldova, largest city of Moldova. The city is Moldova's main industrial and commercial centre, and is located in the middle of the coun ...
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train. A system developed by Talgo and
Construcciones y Auxiliar de Ferrocarriles Construcciones y Auxiliar de Ferrocarriles (Grupo CAF, ) is a Spanish publicly listed company which manufactures railway vehicles and equipment and buses through its Solaris Bus & Coach subsidiary. It is based in Beasain, Basque Autonomous Comm ...
(CAF) of Spain uses variable gauge wheelsets; at the border between France and Spain, through passenger trains are drawn slowly through an apparatus that alters the gauge of the wheels, which slide laterally on the axles.Alberto García Álvarez
"Automatic Gauge Changeover for Trains in Spain"
(PDF), Fundación de los Ferrocarrilos Españoles, 2010.
A similar system is used between China and Central Asia, and between Poland and Ukraine, using the SUW 2000 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 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 , more known as Russian gauge, is the dominant track gauge in former Soviet Union countries ...
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 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., 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 (1931), ''History of the Great Western Railway'', vol. II: 1863–1921, London: Great Western Railway, 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.


Triple gauge

In rare situations, three different gauges may converge on to a rail yard and triple-gauge track is needed to meet the operational needs of the break-of-gauge station – most commonly where there is insufficient space to do otherwise. Construction and operation of triple-gauge track and its signalling, however, involves immense cost and disruption, and is undertaken when no other alternative is available.


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 units 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 ...
, metric units or SI units. Imperial units were established in the United Kingdom by the Weights and Measures Act 1824. The
United States customary units United States customary units form a system of measurement units commonly used in the United States and most U.S. territories since being standardized and adopted in 1832. The United States customary system developed from English units that ...
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: Australia, Canada, New Zealand, South Africa, the United Kingdom and the United States ...
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 (the structure consisting of the rails, fasteners, sleepers/ties and
ballast Ballast is dense material used as a weight 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 ...
(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 between an airport and a nearby city. Direct links operate straight from the airport terminal to the city, while other links require an intermediate use of a people mover or ...
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 railroa ...
in the US 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 and
locomotive A locomotive is a rail transport, rail vehicle that provides the motive power for a train. Traditionally, locomotives pulled trains from the front. However, Push–pull train, push–pull operation has become common, and in the pursuit for ...
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 k ...
), as well as smaller
bridge A bridge is a structure built to Span (engineering), span a physical obstacle (such as a body of water, valley, road, or railway) without blocking the path underneath. It is constructed for the purpose of providing passage over the obstacle, whi ...
s, smaller
tunnel A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and is usually completely enclosed except for the two portals common at each end, though there may be access and ve ...
s (smaller structure gauge). Narrow gauge is thus often used in mountainous terrain, where the savings in
civil engineering Civil engineering is a regulation and licensure in engineering, professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including public works such as roads ...
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 (), sometimes referred to by the Portmanteau, portmanteau Chunnel, is a undersea railway tunnel, opened in 1994, that connects Folkestone (Kent, England) with Coquelles (Pas-de-Calais, France) beneath the English Channel at ...
, a narrow-gauge railway is substantially cheaper and easier to install and remove. Such railways have almost vanished due to the capabilities of modern
truck A truck or lorry is a motor vehicle designed to transport freight, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame construct ...
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 and
locomotive A locomotive is a rail transport, rail vehicle that provides the motive power for a train. Traditionally, locomotives pulled trains from the front. However, Push–pull train, push–pull operation has become common, and in the pursuit for ...
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 k ...
), as well as larger
bridge A bridge is a structure built to Span (engineering), span a physical obstacle (such as a body of water, valley, road, or railway) without blocking the path underneath. It is constructed for the purpose of providing passage over the obstacle, whi ...
s, larger
tunnel A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and is usually completely enclosed except for the two portals common at each end, though there may be access and ve ...
s (larger structure gauge). 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 or
utility In economics, utility is a measure of a certain person's satisfaction from a certain state of the world. Over time, the term has been used with at least two meanings. * In a normative context, utility refers to a goal or objective that we wish ...
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. The specific meaning and etymology of the term and its ...
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 ...
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 (economics), value or utility a user derives from a Goods, good or Service (economics), service depends on th ...
" 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 the Social science, 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 Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...
– the earliest nation to develop and adopt railway technologies – of structure gauges 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, Railroad car#Freight cars, freight and Passenger railroad car, passenger cars (or coaches) ...
of continental Europe to operate in the UK. 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 Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...
, ore, and
gravel Gravel () is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentation, sedimentary and erosion, erosive geological processes; it is also produced in large quantities commercially as crushed stone. Gr ...
, can be mechanically transshipped, but even this is time-consuming, and the equipment required for the transfer is often complex to maintain. 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 railroad car, rolling stock g ...
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), extra cost is involved in designing, manufacturing or importing narrow-gauge equipment. Solutions to interchangeability problems include bogie exchanges, a rollbock system,
dual gauge Dual gauge railroad track has three or four rails, allowing vehicles of two track gauges to run on it. Signalling and sidings are more expensive to install on dual gauge tracks than on two single gauge tracks. Dual gauge is used when there i ...
, variable gauge, or gauge conversion.


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 transport network utilising trains that run significantly faster than those of traditional rail, using an integrated system of specialised rolling stock and dedicated railway track, tracks. While there is ...
lines are built to standard gauge, except in Uzbekistan and Russia.


Europe

The
European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...
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, officially the Republic of Lithuania, 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, bordered by Latvia to the north, Belarus to the east and south, P ...
,
Latvia Latvia, officially the Republic of Latvia, is a country in the Baltic region of Northern Europe. It is one of the three Baltic states, along with Estonia to the north and Lithuania to the south. It borders Russia to the east and Belarus to t ...
, and
Estonia Estonia, officially the Republic of Estonia, is a country in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the Baltic Sea across from Sweden, to the south by Latvia, and to the east by Ru ...
in the building of some key railway lines ( Rail Baltica) 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 in Europe, and SGR in East Africa. It is the ...
, 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
Economic and Social Commission for Asia and the Pacific An economy is an area of the production, distribution and trade, as well as consumption of goods and services. In general, it is defined as a social domain that emphasize the practices, discourses, and material expressions associated with ...
(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, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...
and
Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...
* 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 in Europe, and SGR in East Africa. It is the ...
* 2008: A proposed metre gauge line across Southern
Paraguay Paraguay, officially the Republic of Paraguay, is a landlocked country in South America. It is bordered by Argentina to the Argentina–Paraguay border, south and southwest, Brazil to the Brazil–Paraguay border, east and northeast, and Boli ...
to link Argentina at Resistencia to Brazil at
Cascavel Cascavel is a city in the state of Paraná (state), Paraná in Brazil. It is the fifth most populous city in the state with 364.104 inhabitants, according to IBGE 2024 estimate. The distance to Curitiba, the state capital, is 491 kilometers b ...
; both those lines are , and the new line would allow "bioceanic" running from the Atlantic port of
Paranaguá Paranaguá (Tupi language, Tupi, 'Great Round Sea') is a city in the state of Paraná (state), 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, ...
in
Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
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. Once claimed by Bolivia follo ...
in
Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...
on the Pacific.


Africa

The East African Railway Master Plan is a proposal for rebuilding and expanding railway lines connecting
Ethiopia Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...
,
Djibouti Djibouti, 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 Sea and the Gulf of Aden to the east. The country has an area ...
,
Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...
,
Uganda Uganda, officially the Republic of Uganda, is a landlocked country in East Africa. It 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 ...
,
Rwanda Rwanda, officially the Republic of Rwanda, is a landlocked country in the Great Rift Valley of East Africa, where the African Great Lakes region and Southeast Africa converge. Located a few degrees south of the Equator, Rwanda is bordered by ...
,
Burundi Burundi, officially the Republic of Burundi, is a landlocked country in East Africa. It is located in the Great Rift Valley at the junction between the African Great Lakes region and Southeast Africa, with a population of over 14 million peop ...
,
Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...
,
South Sudan South Sudan (), officially the Republic of South Sudan, is a landlocked country in East Africa. It is bordered on the north by Sudan; on the east by Ethiopia; on the south by the Democratic Republic of the Congo, Uganda and Kenya; and on the ...
and beyond. The plan is managed by infrastructure ministers from participating East African Community 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 in Europe, and SGR in East Africa. It is the ...
. 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 in
Cameroon Cameroon, officially the Republic of Cameroon, is a country in Central Africa. It shares boundaries with Nigeria to the west and north, Chad to the northeast, the Central African Republic to the east, and Equatorial Guinea, Gabon, and the R ...
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 project by the Nigerian Government to create a north–south standard gauge rail link. The first converted segment, between
Abuja Abuja (; , ) is the capital city of the Federal Republic of Nigeria, strategically situated at the geographic midpoint of the country within the Federal Capital Territory (Nigeria), Federal Capital Territory (FCT). As the seat of the Federal G ...
and Kaduna, was completed in July 2016. The
African Union The African Union (AU) is a continental union 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 African Union. The b ...
has a 50-year plan to connect the capital cities and major centres by high-speed railways.


Timeline


See also

*
History of rail transport The history of rail transport began before the beginning of the common era. It can be divided into several discrete periods defined by the principal means of track material and motive power used. Ancient systems The Post Track, a prehisto ...
* List of track gauges * List of tram systems by gauge and electrification *
Rail profile The rail profile is the cross-sectional shape of a Railway track#Rail, rail as installed on a railway or railroad, perpendicular to its length. Early rails were made of wood, cast iron or wrought iron. All modern rails are hot rolled steel ...
* Rail terminology * Rail transport modelling scales * Rapid transit track gauge


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)



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