Track gauge

Indian Narrow and Broad gauge tracks

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

All the vehicles operating over 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 track 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 track gauge of a network and the actual current track gauge at some locality, due to divergence of the track components from the nominal. Railway engineers use a device to measure the actual track gauge, and this device is also referred to (in another sense of the words) as a track gauge.

Nominal track gauge

The nominal track gauge of a railway system is the distance between the inner faces of the rails of an individual track. In current practice it is specified to be measured at a certain distance below the rail head as the inner faces of the rail head (referred to as the gauge faces) are not necessarily vertical.

The rolling stock used on the network must have running gear (wheelsets) that is compatible with the track gauge of the network, and therefore the track gauge is a key parameter in determining interoperability. (In present practice there are many others—see below.) In many cases in the earliest days of railways, the railway company saw itself as an infrastructure provider only, and therefore independent hauliers needed to provide wagons suited to the track gauge. Colloquially the wagons might be referred to as "four feet gauge wagons", say, if the infrastructure had a track 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.

Selection of gauge

Early track technology

Note: the following is a brief generalisation and there were many local exceptions. Some further detail is at and Permanent way (history), wagonway and plateway and an overview is in Early Railways

In the earliest days of railways, single wagons were manhandled on timber rails, almost always in connection with mineral extraction, either 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 alternative methods of guiding the wagons were employed. The rails had to be put at a spacing that suited the wagon wheels.

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 system 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 away from the immediate vicinity of the mine or quarry, typically to a navigable waterway. The wagons would be made to a consistent pattern and as before, the track would be made to suit the wagons, and the gauge—the spacing of the rails—was more critical. The Penydarren Tramroad of 1802 in South Wales, a plateway, spaced these at 4 ft 4in over the outside of the upstands.

Fish-belly cast iron rails from the Cromford and High Peak Railway

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 the weight of the locomotive. 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.

Edge rails required a close match between the rail spacing and the configuration of the wheelsets, and the importance of the track gauge was reinforced. Railway networks were still seen as local concerns, and there was no appreciation of a future connection to other, more remote networks, 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 ft 6in; the Dundee and Newtyle Railway (1831) in the north-east of Scotland adopted 4 ft 6½in; the Redruth and Chasewater Railway (1825) in Cornwall chose 4 ft 0in.

The Arbroath and Forfar Railway opened in 1838 with a gauge of 5 ft 6in, and the Ulster Railway of 1839 used 6 ft 2in

The Stockton and Darlington Railway

An early Stephenson locomotive

Locomotive engines were being developed in the first decades of the nineteenth century; they took various forms but George Stephenson developed a successful locomotive in his work 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, and it adopted the gauge of the Killingworth line, 4 ft 8in. Tomlinson quotes the Durham County Advertiser for 24 May 1822, describing the ceremonial first laying of track on the Stockton and Darlington line:

On Thursday, the 23rd of May [1832]—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 long and 28 lbs in wight, 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 4ft 8in 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 4ft 8in 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 the standard gauge established.

Wood 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 discusses the disparity between 4 ft 8in and 4 ft 8½in in a footnote:

In spite of the definite statement of Nicholas Wood ... that the original gauge of the Stockton and Darlington Railway was 4ft 8½in, there is abundant evidence to show that it was 4ft 8in. The deputation from Liverpool in 1824 found "The width of the railroad, inside, 4ft 8in"; Joseph Pease, on the 28th June, 1839, stated before a Parliamentary Committee, that the width between the rails was 4ft 8in, adding "They are practically 4ft 8½in", 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 was promoted (and opened in 1830), it used the same gauge. The Liverpool and Manchester line—the first inter-city line—was also hugely successful, and the gauge (now eased to 4 ft 8½in), became the automatic choice: "standard gauge".

Broad gauge

The Liverpool and Manchester line was quickly followed by other trunk railways; the Grand Junction Railway and the London and Birmingham Railway forming a huge critical mass of the standard gauge. When Bristol promoters planned a line from London they employed the innovative engineer Isambard Kingdom Brunel. He decided on a wider track gauge, to give greater stability to the coaches, and the railway, the Great Western Railway adopted a gauge of 7 ft 0in, later eased to 7 ft 0¼in. This became known as the broad gauge. The Great Western Railway was a successful network and became much extended, directly and through the medium of friendly associated companies, widening the scope of the broad gauge.

Gauge differences

At the same time other parts of Great Britain built railways using the standard gauge, and British technology was exported to some European countries and parts of North America, also using the standard gauge. Great Britain polarised into areas that had broad gauge lines or standard gauge lines. In this context the standard gauge was referred to as narrow gauge to indicate the contrast. Some smaller concerns also selected other non-standard gauges: the Eastern Counties Railway adopted a gauge of 5 ft 0in. Most of them converted to standard gauge at an early date but the Great Western's broad gauge continued to grow.

At this time the larger railway companies wished to expand geographically, and this took the form of large areas of Great Britain that such a company considered to be under their control. When a new independent line was proposed to open up an as yet unconnected area, the gauge of the proposed line 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 such a line in that choice became very intense, and became referred to as "the gauge wars".

As long-distance passenger and freight transits between networks became increasingly important, the difficulty of moving from broad to narrow gauge or vice versa—the break of gauge became more prominent and more objectionable. The British Parliament intervened with an Act that forbade the construction of new broad gauge lines unconnected with the existing broad gauge network, and the broad gauge network itself was eventually converted—a process called gauge conversion—to standard, progressively until 1892. The same Act mandated the gauge of 5 ft 3in for use in Ireland.

Gauge selection in other countries

Different gauges, from left: 1435mm, 1000mm and 600mm, on display at the China Railway Museum in Beijing

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

Terminology

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, although without qualification it is generally understood to refer to a nominal gauge of 1435mm or 4 ft 8½in (or a locally determined gauge close to those values). 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 refer to track gauges greater or less than the generally adopted standard: they are relative terms.

In the British area of influence in southern Africa, the gauge of 3 ft 6in was widely adopted, and became known as the Cape gauge.

The terms structure gauge and loading gauge have nothing to do 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 for freedom to run on a certain route, 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 decisions on interoperability; these include electro-magnetic compatibility, compliance with control system parameters, and of course axle load and loading envelope in general.

In British practice, the general space between the rails of one track is colloquially referred to as "the four-foot way"; this is contrasted with the space between two tracks: "the six-foot way". These descriptions are simply convenient phrases approximately relating to the respective dimensions.

Narrow gauge

Main article: Narrow gauge railway

In many areas narrow gauge railways have been built. As the gauge of a railway is reduced the costs of construction can also be reduced since narrow gauges allow a 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 and the Rocky Mountains of North America as well as Central Europe and South America.

Industrial railways are often constructed using narrow gauge. Sugar cane and banana plantations are often served by narrow gauges such as 2 ft (610 mm), as there is little through traffic to other systems.

The most widely used narrow gauges on public railways are

• 1067mm Cape gauge (e.g. Southern and Central Africa, Indonesia, Japan, Taiwan, Philippines, parts of Australia, New Zealand, Honduras and Costa Rica.)
• 1000mm metre gauge (e.g. SE Asia, 17,000 km (11,000 mi) in India, East Africa, South America and Central Europe).
• 762mm (e.g. formerly in Sri Lanka Kelani Velley and Udapussellawa lines.

Break of gauge

Main article: Break-of-gauge

A cartoon depicting the horrors of goods transfer at the break of gauge at Gloucester in 1843

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 transportation, and in Great Britain led to political intervention.

Some means of overcoming the problem are used on narrow gauge systems where carrier wagons are used: standard gauge wagons are carried on the narrow gauge system on special vehicles, generally equipped with rails of the wider gauge to enable broad gauge vehicles to roll on and off at transfer points.

On the Transmongolian Railway, Russia and Mongolia use broad gauge while China uses standard gauge. At the border, each carriage is lifted and its bogies are changed. The whole operation can take several hours.

Other examples include crossings into or out of the former Soviet Union: Ukraine/Slovakia border on the Bratislava-L'viv train, and from the Romania/Moldova border on the Chişinău-Bucharest train.

A corresponding system developed by the Talgo company 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.

A similar system is also used between China and Central Asia, and Poland and Ukraine, using the SUW 2000 and INTERGAUGE variable axles systems. China and Poland use standard gauge, while Central Asia and Russia use 1520mm.

Main article: Variable gauge

Mixed gauge

Main article: Dual gauge

Mixed gauge track at Sassari, Sardinia: 1435 and 950 mm

Where a railway corridor needs to be used by trains of two gauges, mixed gauge (or dual gauge) track sections 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.

Mixed gauge track allows trains of different gauges to share the same track. This can save considerable expense compared to using separate tracks for each gauge, but introduces complexities in track maintenance and signalling, as well as requiring speed restrictions for some trains. If the difference between the two gauges is large enough, for example between 4 ft 8½ in and 3 ft 6 in, three-rail dual-gauge is possible, but if the difference is not large enough, for example between 3 ft 6 in and metre gauge (3 ft 3⅜ in), four-rail dual-gauge is used. Dual-gauge rail lines are used in the railway networks of Switzerland, Australia, Argentina, Brazil, North Korea, Spain, Tunisia and Vietnam.

Reconstructed mixed gauge track at Didcot Railway Museum, England

On the Great Western Railway in Great Britain there was an extended period between the political intervention in 1846 which effectively prevented major expansion of the company's broad gauge system, 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 that in many cases narrow 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 give an illustration and description.

It is known that in some cases mixed gauge trains operated, conveying wagons of both gauges. For example, MacDermot 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 for actual 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 4 ft 8 in (1,422mm) and 4 ft 9½ in (1,460mm).

Dominant gauges

Sixty per cent of the world's railways use Stephenson's 4 ft 8½ in (1,435mm) standard gauge.

ft′ in″	mm	The dominant rail gauge in each country shown
5′ 6″	1676
5′ 5⅔″	1668
5′ 3″	1600
5′	1524
4′ 11⅚″	1520
4′ 8½″	1435
4′ 6″	1372
3′ 6″	1067
3′ 5⅓″	1050
3' 3⅜″	1000
3′ 1⅜″	950
3′	914
2′ 6″	762
2′ 5½″	750
2′	610
1′ 11⅝″	600

Further information: List of rail gauges

Gauge	Name	Installation (km)	Installation (miles)	Usage
1,676 mm (5 ft 6 in)	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)
1,668 mm (5 ft 5 2⁄3 in)	Iberian gauge	15,394	9,565	Portugal, Spain. Sometimes referred to as the 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). The Portuguese network is actually at 1674mm The Portuguese Rede Ferroviária Nacional (REDE) managed 2,650 km of this gauge of this track at the same date.
1,600 mm (5 ft 3 in)	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)
1,524 mm (5 ft)	Russian gauge	5,865	3,644	Finland (contiguous to and generally compatible with 1,520 mm (4 ft 11 5⁄6 in))
1,520 mm (4 ft 11 5⁄6 in)	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 1,524 mm (5 ft))
1,435 mm (4 ft 8 1⁄2 in)	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 Philippines. Also high-speed lines in Japan, Taiwan and Spain. (approx. 60% of the world's railways)
1,067 mm (3 ft 6 in)	Cape gauge	112,000	70,000	Southern and Central Africa, Indonesia, Japan, Taiwan, Philippines, New Zealand, Queensland Australia Queensland Rail (approx. 9% of the world's railways)
1,000 mm (3 ft 3 3⁄8 in)	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)

Future

Further convergence of rail gauge use seems likely, as individual countries seek to build inter-operable national networks, and international organisations seek to build macro-regional and continental networks. National projects include Australian and Indian efforts to create a uniform gauge in their national networks. The European Union has set out to develop inter-operable freight and passenger rail networks across the EU area, and is seeking to standardise track gauge, signalling and electrical power systems. EU funds have been dedicated to assist Baltic states of Lithuania, Latvia, and Estonia in the construction of some key railway lines (Rail Baltica) in the standard gauge instead of their 1520mm gauge, 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.

However the process of 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 a 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 the proposed corridors would encounter one or more breaks of gauge as they cross Asia. Current plans have mechanized facilities at the breaks of gauge to move shipping containers from train to train rather than widespread gauge conversion.

• Rail lines for iron ore to Oakajee port in Western Australia are proposed to form a combined dual gauge network.
• Rail lines for iron ore to Kribi in Cameroon are likely to be 1435 mm with a likely connection to the same port from the 1000 mm gauge 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 to build a high-speed electrified line to connect Kenya with southern Sudan. Kenya and Uganda use metre (1,000 mm (3 ft 3 ³⁄₈ in)} gauge, while Sudan uses 3 ft 6 in (1,067 mm) gauge. Standard gauge was proposed for the project.

Latin America

• 2008: Proposed link between Venezuela and Colombia
• 2008: Venezuela via Brazil to Argentina - standard gauge
• 2008: A proposed metre gauge line across Southern Paraguay to link the Argentine rail at Resistencia to the Brazilian line at Cascavel; both those lines are metre gauge, and the new line would allow uninterrupted "bioceanic" running from one coast to the other, from the Atlantic port of Paranaguá in Brazil to that of Antofagasta in Chile on the Pacific.

Temporary Way - Permanent Way

The temporary way is so called because it is the temporary track often used for construction purposes which is 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 a 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. Thus the Airport Rail Link in Sydney had construction trains of 900 mm (2 ft 11 ⁷⁄₁₆ in) gauge which were replaced by the permanent tracks of 1,435 mm (4 ft 8 ¹⁄₂ in) gauge.

During World War I trench warfare had led to a relatively static disposition of infantry forces 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.

During World War II, it was proposed to expedite a Yunnan-Burma railway using a gauge of 1 ft 3.3in, since such a small gauge facilitates the tightest of curves in difficult terrain.

Pioneers

• 1,435 mm (4 ft 8 ¹⁄₂ in) - 1825 - adopted by George Stephenson
• 2,140 mm (7 ft ¹⁄₄ in) - 1838 - rationally determined by I. K. Brunel
• 597 mm (1 ft 11 ¹⁄₂ in) - 1836 - pioneered by Festiniog Railway for mountainous terrain - often equated as 610 mm (2 ft) gauge.
• 1,600 mm (5 ft 3 in) - 1840s - pioneered in Ireland as a compromise
• 1,676 mm (5 ft 6 in) - 1853 - pioneered by Lord Dalhousie in India
• 1,067 mm (3 ft 6 in) - 1870s - pioneered by Carl Pihl in Norway to reduce costs
• 762 mm (2 ft 6 in) - 1887 - pioneered by Everard Calthrop to reduce costs.

See also

List of rail gauges Loading gauge Structure gauge Rail terminology Longest trains

Rail transport by country History of rail transport by country Breitspurbahn Gauge conversion Heaviest trains

Minimum railway curve radius Third rail Rail transport modelling scales Model railway scales

External links

• A history of track gauge by George W. Hilton
• Railroad Gauge Width — 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 Indian Railways FAQ: Gauges
• The Days they Changed the Gauge in the U.S. South