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Rail gauge


Rail gauge

Track gauges
General concepts
Track gauge · Break-of-gauge ·

Dual gauge · Conversion (list·
Bogie exchange · Variable gauge

By transport mode
Tram · Rapid transit · High-speed rail
Miniature · Scale model
By size (list)

  Breitspurbahn 3,000 mm (9 ft 10 18 in)
  Brunel 2,140 mm (7 ft 14 in)
  Indian 1,676 mm (5 ft 6 in)
  Iberian 1,668 mm (5 ft 5 2132 in)
  Irish 1,600 mm (5 ft 3 in)
  Pennsylvania 1,588 mm
1,581 mm
(5 ft 2 12 in)
(5 ft 2 14 in)
  Russian 1,524 mm
1,520 mm
(5 ft)
(4 ft 11 2732)

  Standard 1,435 mm (4 ft 8 12 in)

  Scotch 1,372 mm (4 ft 6 in)
  Cape 1,067 mm (3 ft 6 in)
  Metre 1,000 mm (3 ft 3 38 in)
  Three foot 914 mm (3 ft)
  Imperial and Bosnian 762 mm
760 mm
750 mm
(2 ft 6 in)
(2 ft 5 1516 in)
(2 ft 5 12 in)
  2 ft and 600mm 610 mm
600 mm
597 mm
(2 ft)
(1 ft 11 58 in)
(1 ft 11 12 in)

  Fifteen-inch 381 mm (15 in)
By location
North America · South America · Europe

Track gauge is a technical term used in rail transport to define the spacing of the rails on a railway track.

All vehicles on a network must have running gear that is compatible with the track gauge, and in the earliest days of railways selection of a proposed railway's gauge was a key issue.

As the dominant parameter determining interoperability, it is still frequently used as a descriptor of a route or network.

There is a distinction between the nominal gauge and actual gauge at some locality, due to divergence of track components from the nominal. Railway engineers use a device to measure the actual gauge, and this device is also referred to as a track gauge.

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.

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.


Track is defined in Imperial units or in metric units: metric definitions are sometimes re-definitions.

Imperial units were established by The Weights and Measures of Act of 1824. The United States customary units for length did not agree with the Imperial system until 1959, when one International yard was defined as 0.9144 meters, i.e. 1 foot as 0.3048 meter and 1 inches as 25.4 mm.

The list shows the Imperial and other units that have been used for track gauge definitions:

Unit SI-equivalent Track gauge example
Imperial feet 304.8 mm
Castilian feet 278.6 mm 6 Castilian feet = 1,672 mm (5 ft 5 56 in) (2 Castilian feet = 558 mm, 1 ft 9 3132 in)
Portuguese feet 5 Portuguese feet = 1,664 mm (5 ft 5 12 in)
Swedish feet 296.904 mm 3 Swedish feet = 891 mm (2 ft 11 110 in), 2.7 Swedish feet = 802 mm (2 ft 7 35 in)
Prussian feet (Rheinfuß) 313.85 mm 2 12 Prussian feet = 785 mm (2 ft 6 910 in)
Austrian fathom 12 Austrian fathom = 760 mm (2 ft 5 1516 in)

Selection of gauge

Early track technology

The following is a brief generalisation and there were many local exceptions. Further detail is at Permanent way (history), wagonway and plateway, and an overview is in Early Railways[1]

In the earliest days of railways, single wagons were manhandled on timber rails, almost always in connection with mineral extraction, within a mine or quarry or leading from it. Guidance was not at first provided except by human muscle power, but later a number of methods of guiding the wagons were employed. The rails had to be at a spacing that suited the wagon wheels.[2]

The timber rails wore rapidly and later flat cast-iron plates were provided to limit the wear. In some localities the plates were made L-shaped, the upstand of the L providing the guidance; this is generally referred to as a "plateway".

As the guidance of the wagons was improved, short strings of wagons could be connected and pulled by 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 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.[3]

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.[1]

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 (1826) in the West of Scotland used ;[4] the Dundee and Newtyle Railway (1831) in the north-east of Scotland adopted ;[5] the Redruth and Chasewater Railway (1825) in Cornwall chose .[6]

The Arbroath and Forfar Railway opened in 1838 with a gauge of ,[7] and the Ulster Railway of 1839 used [7]

The Stockton and Darlington Railway

Locomotives were being developed in the first decades of the nineteenth century; they took various forms, but George Stephenson developed a successful locomotive on the Killingworth Wagonway, where he worked. His designs were so successful that they became the standard, and when the Stockton and Darlington Railway was opened in 1825 it used his locomotives, with the same gauge as the Killingworth line, .[8] Tomlinson quotes the Durham County Advertiser for 24 May 1822, describing the ceremonial first laying of track:

On Thursday, the 23rd of May [1822]—the formal inauguration of the railway took place in connection with the laying of the first rails. There was much rejoicing at Stockton on this occasion, which was recognised as a memorable one in the history of the town.
[The Chairman] Mr Meynell took his stand near the small brick house adjoining the line, not far from the window that looks towards the crossing, the Mayor and Recorder and other local dignitaries facing him, and, without any preliminary observations, laid several rails of the new road—malleable iron bars, 15 feet (4.6 m) long and 28 lb (13 kg) in weight, the first to be used by a public railway company. A royal salute was fired and the band struck up "God Save the King" as he fixed them in position.
More was accomplished this day than could be foreseen. Not only was there laid near St John's Well the first of an illimitable series of rails which in a few years were to connect the most distant parts of the earth, and produce incalculable social changes, but Mr Meynell, in placing these first rails apart, practically determined the standard gauge of Great Britain, a gauge that has enabled the principal railways of the world and their rolling stock to be constructed and maintained at a minimum cost, while admitting of the remarkable developments in speed and carrying capacity which have been witnessed in the last few years.
For the Stockton and Darlington Railway, as for the Hetton Colliery Railway, George Stephenson had adopted the gauge of the Killingworth Waggonway, the earliest position of which—from Willington Square to Willington Quay—was laid in 1762. To this date, at least, must the 4 ft 8 in gauge be referred, for it is extremely improbable that, when a branch was formed from Killingworth Colliery in 1806 to the old waggonway of the "Grand Allies", from Longbenton Colliery, (which was still working near Benton Square), the gauge was in any way altered, especially as the Willington coals also at this time went down to the river in wagons having the same width between the wheels.

Thus was standard gauge established.

Wood[9] wrote in 1838 (page 138):

The first public railway, of any extent, which was executed, was the Stockton and Darlington Railway, the engineer being Mr. George Stephenson. The width, between the rails, of that railway, was made four feet eight inches and a half, taking the Killingworth Railway as a standard. The Liverpool and Manchester Railway, also constructed by Mr. Stephenson, was formed of the same width ...

Tomlinson[8] discusses the disparity between 4 ft 8 in and 4 ft 8 12 in in a footnote:

In spite of the definite statement of Nicholas Wood ... that the original gauge of the Stockton and Darlington Railway was , there is abundant evidence to show that it was . The deputation from Liverpool in 1824 found "The width of the railroad, inside, ; Joseph Pease, on the 28th June, 1839, stated before a Parliamentary Committee, that the width between the rails was , adding "They are practically , and John Dixon, the engineer of the company, in a note on the Whitehaven Junction Railway in 1846, confirms this statement:— "And I, (John Dixon) can testify to the fact of there being half an inch difference in the gauge of the Great North of England Railway and the Stockton and Darlington Railway, and that engines and carriages reciprocally travel on each line daily without danger or a suspicion thereof from that cause: indeed, the fact of this difference is not generally known."

The Stockton and Darlington line was immensely successful, and when the Liverpool and Manchester Railway, the first inter-city line, was promoted (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".

Broad gauge

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 critical mass of standard gauge. When Bristol promoters planned a line from London they employed the innovative engineer Isambard Kingdom Brunel. He decided on a wider gauge, to give greater stability, and the Great Western Railway adopted a gauge of , later eased to . This became known as broad gauge. The GWR was successful and became greatly extended, directly and through friendly associated companies, widening the scope of broad gauge.

Gauge differences

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 areas that had broad gauge lines or standard gauge lines. 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 passengers and freight between the gauges became increasingly important, the difficulty of moving from one gauge to the other — the break of gauge - became more prominent and more objectionable. Parliament intervened with an Act that forbade the construction of broad gauge lines unconnected with the broad gauge network, and the broad gauge network was eventually converted—a process called gauge conversion—to standard, progressively until 1892. The same Act mandated the gauge of for use in Ireland.[10]

Gauge selection in other countries

As railways were adopted in other countries, the gauge selected was pragmatic; in some cases standard gauge was adopted, but many countries chose a different gauge as their national gauge, either by Governmental policy or as a matter of individual choice. Narrow gauges were used in mountainous regions as construction costs tend to be lower, and became widespread, and in some countries multiple gauges were chosen by long-distance networks, particularly in India and Australia.


The terms standard gauge, broad gauge and narrow gauge do not have any fixed meaning. A "standard" gauge is only standard in a geographical region where it is dominant, but it is generally understood to be . An infrastructure owner would be ill-advised to order track materials simply as "standard gauge", but would normally specify the required critical dimensions of the components.

Broad gauge and narrow gauge are relative to the generally adopted standard.

In the British area of influence in southern Africa, was widely adopted, and became known as the Cape gauge.

The terms structure gauge and loading gauge have little connection with track gauge. They are both widely used, but imprecise, terms. Structure gauge describes the cross-section envelope into which new or altered structures (bridges, lineside equipment etc.) must not encroach. Loading gauge is the corresponding cross-sectional profile within which rail vehicles and their loads must be contained. If an exceptional load or a new type of vehicle is being assessed to run, it must conform to the route's loading gauge.

Historically a space between the two profiles was required to allow for dynamic effects, extreme wear and surveying tolerances, but in current practice all tolerances are incorporated into the vehicle operating profile and no other allowance is necessary.

Nowadays there are other parameters that must be assessed for interoperability, including electro-magnetic compatibility, compliance with control system parameters, axle load and loading envelope.

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.

Narrow gauge

Main article: Narrow gauge railway

As the gauge of a railway is reduced the costs of construction can be reduced since narrow gauges allow smaller-radius curves, allowing obstacles to be avoided rather than having to be built over or through (valleys and hills); the reduced cost is particularly noticeable in mountainous regions, and many narrow gauge railways were built in Wales, the Rocky Mountains of North America, Central Europe and South America.

Industrial railways are often narrow gauge. Sugar cane and banana plantations are often served by narrow gauges such as , as there is little through traffic to other systems.

The most widely used narrow gauges on public railways are

  • Cape gauge (Southern and Central Africa, Indonesia, Japan, Taiwan, Philippines, parts of Australia, New Zealand, Honduras and Costa Rica.)
  • metre gauge (SE Asia, 17,000 km (11,000 mi) in India, East Africa, South America and Central Europe).
  • (formerly in Sri Lanka Kelani Velley and Udapussellawa lines.

Break of gauge

Main articles: Break-of-gauge and Variable gauge

Through operation between railway networks with different gauges was originally impossible; goods had to be transhipped 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 wagons 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 standard gauge. 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 Chişinău-Bucharest train.[11]

A system developed by Talgo and Construcciones y Auxiliar de Ferrocarriles (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. This is fully described in Automatic Gauge Changeover for Trains in Spain.[12]

A similar system is used between China and Central Asia, and between Poland and Ukraine, using the SUW 2000 and INTERGAUGE variable axle systems.[13] China and Poland use standard gauge, while Central Asia and Russia use .

Mixed gauge

Main article: Dual gauge

Where a railway corridor is used by trains of two gauges, mixed gauge (or dual gauge) track can be provided, in which three rails are supported in the same track structure. This arose particularly when individual railway companies chose different gauges and subsequently required to share a route; this is most commonly found at the approaches to city terminals, where land space is limited.

Trains of different gauges sharing the same track can save considerable expense compared to using separate tracks for each gauge, but introduces complexities in track maintenance and signalling, and may require speed restrictions for some trains. 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-rail triple-gauge is used. Dual-gauge rail lines are used in Switzerland, Australia, Argentina, Brazil, North Korea, Spain, Tunisia and Vietnam.

On the GWR there was an extended period between political intervention in 1846 that prevented major expansion of its broad gauge[note 1] and the final gauge conversion to standard gauge in 1892.

During this period there were many locations where practicality required mixed gauge operation, and in station areas the track configuration was extremely complex. This was compounded by the fact that the common rail had to be at the platform side in stations, so 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. Jenkins and Langley[14] give an illustration and description.

In some cases mixed gauge trains operated, conveying wagons of both gauges. For example, MacDermot[15] says:

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.

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 in the USA specifies that the actual gauge of track that is rated for a maximum of 60 mph (96.6 km/h) must be between and .[16]

Dominant gauges

Sixty per cent of the world's railways use .

Further information: List of track gauges
Gauge Name Installation (km) Installation (miles) Usage
Indian gauge 78,500 48,800 India (42,000 km or 26,000 mi; increasing with Project Unigauge), Pakistan, Argentina 24,000 km or 15,000 mi, Chile, Sri Lanka 1,508 km or 937 mi
(approx. 6.67% of the world's railways)
Iberian gauge 15,394 9,565 Portugal, Spain. Sometimes referred to as Iberian gauge. In Spain the Administrador de Infraestructuras Ferroviarias (ADIF) managed 11,683 km of this gauge and 22 km of mixed gauge at end of 2010.[17] The Portuguese network is actually at 1674mm[note 2] The Portuguese Rede Ferroviária Nacional (REFER) managed 2,650 km of this gauge of this track at the same date.[17]
Irish gauge 9,800 6,100 Ireland (1,800 km or 1,100 mi), and in Australia mainly Victoria and some South Australia Victorian gauge (4,017 km or 2,496 mi), Brazil (4,057 km or 2,521 mi)
Russian gauge 5,865 3,644 Finland (contiguous to and generally compatible with )
Russian gauge 220,000 140,000 CIS states, also Estonia, Georgia, Latvia, Lithuania, Mongolia
(approx. 17% of the world's railways; all contiguous — redefined from )
Standard gauge 720,000 450,000 Europe, Argentina, United States, Canada, China, Korea (South), Korea (North), Australia, Indonesia (only at Aceh), Middle East, North Africa, Mexico, Cuba, Panama, Venezuela, Peru, Uruguay and the Philippines. Also high-speed lines in Japan, Taiwan and Spain.
(approx. 60% of the world's railways)
Cape gauge 112,000 70,000 Southern and Central Africa, Indonesia, Japan, Taiwan, Philippines, New Zealand, Queensland Australia, Queensland Rail, Western Australia
(approx. 9% of the world's railways)
Metre gauge 95,000 59,000 SE Asia, India (17,000 km or 11,000 mi, decreasing with Project Unigauge), Argentina (11,000 km or 6,800 mi), Brazil (23,489 km or 14,595 mi), Bolivia, northern Chile, Switzerland (RhB, MOB, BOB, MGB), East Africa
(approx. 7% of the world's railways)


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. National projects include Australian and Indian efforts to create a uniform gauge. The European Union 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, Latvia, and Estonia in the conversion of some key railway lines (Rail Baltica) to standard gauge, replacing 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.

Gauge conversion of existing lines is extremely expensive and it is likely that only primary trunk routes will be converted, with new strategic lines being built to standard gauge.

The interoperability problem within the EU is not only rail gauge but also loading gauge, especially for the United Kingdom, which has standard rail gauge but generally one of the smallest loading gauges in the world.

New lines

The United Nations Economic and Social Commission for Asia and the Pacific (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 from train to train rather than widespread gauge conversion.

  • Lines for iron ore to Oakajee port in Western Australia are proposed to form a combined dual-gauge network.
  • Lines for iron ore to Kribi in Cameroon are likely to be with a likely connection to the same port from the Cameroon system. This line owned by Sundance Resources may be shared with Legend Mining.

Kenya-Uganda-Sudan proposal

A proposal was aired in October 2004 [18] [19] [20] to build a high-speed electrified line to connect Kenya with southern Sudan. Kenya and Uganda use , while Sudan uses gauge. Standard gauge was proposed for the project.

Latin America

Temporary Way - Permanent Way

The temporary way is the temporary track often used for construction, replaced by the permanent way (the structure consisting of the rails, fasteners, sleepers/ties and ballast (or slab track), plus the underlying subgrade) when construction nears completion. In many cases narrow-gauge track was 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 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.[23]

During World War II, it was proposed to expedite a Yunnan-Burma railway using a gauge of (15.24 in.), since such tiny or "toy" gauge facilitates the tightest of curves in difficult terrain.[24]


See also



External links

  • 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)
  • The Days they Changed the Gauge in the U.S. South
  • Juan Manuel Grijalvo - The Myth of the "Standard" Gauge
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