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The standard gauge (also named the Stephenson gauge after George Stephenson, UIC (track) gauge, International gauge or normal gauge) is a widely-used railway track gauge. Approximately 60% of the world's existing railway lines are built to this gauge (see the list of countries that use the standard gauge). Except for Russia and Finland, all high-speed lines have been built to this gauge.
The distance between the inside edges of the rails of standard gauge track is usually called 1,435 mm but in the United States it is still called 4 ft 8 1⁄2 in.
It is called "uniform gauge" in Queensland.
As railways developed and expanded one of the key issues to be decided was that of the track gauge (the distance, or width, between the inner sides of the rails) that should be used. The eventual result was the adoption throughout a large part of the world of a “standard gauge” of 4 ft 8 1⁄2 in allowing inter-connectivity and the inter-operability of trains.
In England some early lines in colliery (coal mining) areas in the northeast of the country were built to a gauge of 4 ft 8 in (1,422 mm); and in Scotland some early lines were 4 ft 6 in (1,372 mm) (Scotch gauge). By 1846, in both countries, these lines were widened to standard gauge. Parts of the United States rail system, mainly in the Northeast, adopted the same gauge because some early trains were purchased from Britain. However, until well into the second half of the 19th century Britain and the USA had several different track gauges. The American gauges converged over time as the advantages of equipment interchange became increasingly apparent; notably, the South's 5 ft (1,524 mm) broad gauge system was converted to be compatible with standard gauge over the course of two days, beginning May 31, 1886. See Track gauge in the United States.
With the advent of metrication, standard gauge was redefined as 1,435 mm, a reduction of 0.1 mm, but well within existing tolerance limits. The exception is the United States, where standard gauge continues to be defined in terms of customary units.
A popular legend that has been around since at least 1937 traces the origin of the 4 ft 8 1⁄2 in gauge even further back than the coalfields of northern England, pointing to the evidence of rutted roads marked by chariot wheels dating from the Roman Empire.[Note 1] Snopes categorized this legend as false but commented that “... it is perhaps more fairly labelled as 'True, but for trivial and unremarkable reasons.'" The historical tendency to place the wheels of horse-drawn vehicles approximately 5 feet (1,500 mm) apart probably derives from the width needed to fit a carthorse in between the shafts. In addition, while road-traveling vehicles are typically measured from the outermost portions of the wheel rims (and there is some evidence that the first railroads were measured in this way as well), it became apparent that for vehicles travelling on rails it was better to have the wheel flanges located inside the rails, and thus the distance measured on the inside of the wheels (and, by extension, the inside faces of the rail heads), was the important one.
There was no standard gauge for horse railways, but there were rough groupings: in the north of England none were less than 4 ft (1,219 mm). Wylam colliery's system, built before 1763, was 5 ft (1,524 mm); as was John Blenkinsop's Middleton Railway, the old 4 ft (1,219 mm) plateway was relaid to 5 ft (1,524 mm) so that Blenkinsop's engine could be used. Others were 4 ft 4 in (1,321 mm) Beamish or 4 ft 7 1⁄2 in (Bigges Main and Kenton and Coxlodge).
The English railway pioneer George Stephenson spent much of his early engineering career working for the coal mines of County Durham. He favoured 4 ft 8 in (1,422 mm) for wagonways in Northumberland and Durham and used it on his Killingworth line. The Hetton and Springwell wagonways also used this gauge.
Stephenson's Stockton and Darlington railway (S&DR) was built primarily to transport coal from several mines near Shildon to the port at Stockton-on-Tees. The S&DR's initial track gauge of 4 ft 8 in (1,422 mm) was set to accommodate the existing gauge of hundreds of horse-drawn chaldron wagons that were already in use on the wagonways in the mines. The railway was built and used at this gauge for fifteen years before a change was made to 4 ft 8 1⁄2 in gauge.
The beginnings of the 4 ft 8 1⁄2 in gauge 
George Stephenson used the 4 ft 8 1⁄2 in gauge (with a belated extra 1⁄2 in (13 mm) of free movement to reduce binding on curves) for the Liverpool and Manchester Railway, authorised in 1826 and opened 30 September 1830. The success of this project led to George Stephenson and his son Robert being employed to engineer several other larger railway projects. However, the Chester and Birkenhead Railway, authorised on 12 July 1837, used 4 ft 9 in (1,448 mm); the Eastern Counties Railway, authorised on 4 July 1836, used 5 ft (1,524 mm); London and Blackwall Railway, authorised on 28 July 1836, used 5 ft (1,524 mm); the London and Brighton Railway, authorised on 15 July 1837, used 4 ft 9 in (1,448 mm); the Manchester and Birmingham Railway, authorised on 30 June 1837, used 4 ft 9 in (1,448 mm); the Manchester and Leeds Railway, authorised on 4 July 1836, used 4 ft 9 in (1,448 mm) and the Northern and Eastern Railway, authorised on 4 July 1836, used 5 ft (1,524 mm) gauge. The 4 ft 9 in (1,448 mm) railways were intended to take 4 ft 8 1⁄2 -gauge vehicles and allow a (second) running tolerance.
The influence of the Stephensons' appears to be the main reason that the 4 ft 8 1⁄2 in gauge became the standard, and its use became more widespread than any other gauge.
During the "gauge war" with the Great Western Railway, standard gauge was called "narrow gauge". The modern use of narrow gauge, for gauges less than standard, did not arise for twenty years until the first such locomotive-hauled passenger railway, the Ffestiniog.
The Royal Commission 
In 1845, in the United Kingdom of Great Britain and Ireland, a Royal Commission reported in favour of a standard gauge. In Great Britain, Stephenson's gauge was chosen as the standard gauge on the grounds that lines already built to this gauge were eight times longer than those using the rival 7 ft 1⁄4 in (2,140 mm) gauge adopted principally by the Great Western Railway. The subsequent Gauge Act ruled that new passenger-carrying railways in Great Britain should be built to a standard gauge of 4 ft 8 1⁄2 in (1,435 mm), and those in Ireland to a new standard gauge of 5 ft 3 in (1,600 mm). It allowed the broad-gauge companies in Great Britain to continue repairing their tracks and expanding their networks within the "Limits of Deviation" and the exceptions defined in the Act. After an intervening period of mixed-gauge operation (tracks were laid with three running-rails), the Great Western Railway finally converted its entire network to standard gauge in 1892.
The Royal Commission made no comment about small, to-be-called "narrow"-gauge lines, such as the Festiniog Railway, which allowed a future multiplicity of small gauges in the UK; it also made no comments about future gauges in British colonies.
Robert Stephenson was reported to have said that if he had a second chance to choose a standard gauge, he would choose one wider than 1,435 mm (4 ft 8 1⁄2 in).  "I would take a few inches more, but a very few".
Road vehicles 
Several states in the United States had laws requiring that road vehicles have a consistent gauge to allow vehicles to more easily follow ruts in the road. These gauges were roughly similar to the railway standard gauge.
- United Kingdom: Railway Regulation (Gauge) Act 1846
|Algeria||Société Nationale des Transports Ferroviaires, Algiers Metro, Algiers tramway, Constantine tramway, Oran tramway, Oran Metro|
|Argentina||Railroad Development Corporation, formerly the Urquiza Line||Other lines are mostly 1,676 mm (5 ft 6 in) broad gauge (Indian gauge)|
|Australia||Pacific National, Pilbara Railways|
|Belgium||NMBS/SNCB, Brussels Metro and tramway|
|Bosnia and Herzegovina||Željeznice Federacije Bosne i Hercegovine and Željeznice Republike Srpske,
|Brazil||Estrada de Ferro do Amapá 1,440 mm (4 ft 8 11⁄16 in); from Uruguaiana to the border to Argentina and from Santana do Livramento to the order to Uruguay (both mixed gauge 4 ft 8 1⁄2 in and 1,000 mm (3 ft 3⅜ in));
Remaining tracks at Jaguarão (Rio Grande do Sul) currently inoperable
|Estrada de Ferro do Amapá, Jane's World Railways 1969/1970 edition gives 4 ft 8 1⁄2 in|
|Bulgaria||National Railway Infrastructure Company (NRIC),
Bulgarian State Railways (BDZ),
Part of Sofia Tramway system
|Canada||Canadian Pacific Railway, Canadian National Railways, Via Rail, BC Rail, SRY, SkyTrain (Vancouver), West Coast Express (Vancouver), O-Train, GO Transit, Chemins de fer Québec-Gatineau, Edmonton Light Rail Transit, C-Train, Scarborough RT (Toronto Transit Commission)|
|Chad||Proposed 2012. |
|China||China Railway High-speed, China Railways, and all rapid transit systems.||Most lines are in standard gauge and Chinese law requires all new state-funded lines to be built with standard gauge. Some meter-gauge and narrow-gauge lines built earlier are still in operation in some areas.|
|Colombia||Metro de Medellín, Tren del Cerrejón, Metro de Bogota|
|Cuba||Ferrocarriles de Cuba|
|Czech Republic||České dráhy
all tram systems in the country (Liberec has dual gauge 1000/1435 mm, with one meter-gauge interurban line to Jablonec nad Nisou)
Funicular in Prague
|Denmark||Banedanmark and Copenhagen Metro|
|Egypt||Egyptian National Railways|
|Estonia / Latvia / Lithuania / Belarus||Eesti Raudtee||Re-gauging all existing system from 1,520 mm (4 ft 11 ⅚ in) and mounting some industrial railways during World War II; 1944-45 all railways re-gauged to 1,520 mm (4 ft 11 ⅚ in).|
|Finland||Finnish Rail Administration||Only at Turku ferry terminal for train ferries to Stockholm, and a freight yard in Tornio.|
|France||SNCF, RATP (on RER lines)|
|Greece||Hellenic Railways Organisation (operated by TrainOSE)||All modern Greek network, except in the Peloponnese|
|Hong Kong||MTR (former KCR network - East Rail Line, West Rail Line, Ma On Shan Line, Light Rail)||Other MTR lines use 1,432 mm (4 ft 8⅜ in), instead of 4 ft 8 1⁄2 in|
Tram systems in Budapest, Debrecen, Miskolc, Szeged
Budapest cogwheel railway
|India||Only used for rapid transit systems: Delhi Metro (Phase 2), Bangalore Metro, Calcutta Tramway, etc.||Indian heavy rail systems (Indian Railways) use 1,676 mm (5 ft 6 in) Indian broad gauge. The majority of under construction and future Metro Rail systems prefer Standard Gauge.|
|Indonesia||Built in Aceh Province|
|Iran||Islamic Republic of Iran Railways|
|Ireland||Railway Procurement Agency||Luas in Dublin|
|Israel||Israel Railways, CTS - operating the Jerusalem Light Rail|
|Italy||Ferrovie dello Stato|
|Japan||Shinkansen, JR Hokkaido Naebo Works (see Train on Train), Keisei Line, Keikyu Line Tokyo Metro Ginza Line, Tokyo Metro Marunouchi Line, Toei Asakusa Line, Toei Oedo Line, Kintetsu Corp (not including the Minami-Osaka Line (1,067 mm), etc.), Keihan Railway, Hankyu Railway, Hanshin Railway, Kyoto Municipal Subway, Osaka Municipal Subway.|
|Lebanon||All lines out of service and more or less dismantled|
|Libya||network under construction|
|Lithuania||Line to Šeštokai from Poland (mixed gauge between Mockava and Šeštokai)|
|Malaysia||RapidKL (Kelana Jaya Line, Ampang Line), KLIA Ekspres|
|Montenegro||Željeznice Crne Gore||3|
|Morocco||Rail transport in Morocco|
|Netherlands||Nederlandse Spoorwegen and regional railways.|
|North Korea||Railways of the DPRK.|
|Norway||Norwegian National Rail Administration, Rail transport in Norway|
|Panama||Panama Railway||since 2000|
|Paraguay||Ferrocarril Presidente Don Carlos Antonio López, now Ferrocarril de Paraguay S.A. (FEPASA)||Now working on 36 km out of Asunción as a tourist steam line; also on 5 km from Encarnación to the border of Argentina, carrying mainly exported soy; the rest of the 441 km of the line awaits its fat, while redevelopment plans come and go with regularity. The section from west of Encarnación to north of San Salvador and the complete San Salvador - Abaí branch have been dismantled by the railway itself to get funds through selling scrap.|
|Peru||Railroad Development Corporation Ferrocarril Central Andino Callao - Lima - La Oroya - Huancayo, La Oroya - Cerro del Pasco ; Ferrocarril del sur de Peru operated by Peru Rail Matarani - Arequipa - Puno and Puno - Cuzco; Ilo - Moquegua mining railroad; Tacna - Arica (Chile) international line, operated by Tacna province; Electric suburban railway of Lima|
|Philippines||Manila Light Rail Transit and Manila Metro Rail Transit.|
|Poland||Polskie Koleje Państwowe, Warsaw Metro, most tramway systems throughout the country|
|Portugal||Planned high-speed lines; Braga funicular; Lisbon Metro; Metro do Porto (adapted from former 1000 mm tracks); Almada light rail.||All other 1,668 mm (5 ft 5 ⅔ in) (broad gauge) and some 1,000 mm (3 ft 3⅜ in) (meter gauge).|
|Romania||Căile Ferate Române|
|Russia||Rostov-on-Don tramway, lines connecting Kaliningrad with Poland|
|Saudi Arabia||Rail transport in Saudi Arabia|
|Slovakia||Železnice Slovenskej republiky, Košice tramway system|
|South Africa||Gautrain in Gauteng Province||Rest of country uses Cape Gauge|
|Spain||AVE High-Speed Train lines from Madrid to Seville, Málaga, Saragossa, Barcelona (-Perthus), Toledo, Huesca and Valladolid, Barcelona Metro L2, L3, L4, L5 lines. Barcelona FGC lines L6, L7, and Metro Vallès S1, S2, S5, S55.||All other 1,668 mm (5 ft 5 ⅔ in) (broad gauge) and some 1,000 mm (3 ft 3⅜ in) (meter gauge).|
|Sweden||Swedish State Railways|
|Switzerland||Swiss Federal Railways|
|Taiwan||Taipei Rapid Transit System, Taiwan High Speed Rail, and Kaohsiung Mass Rapid Transit|
|Thailand||Bangkok Skytrain, Bangkok Metro and Suvarnabhumi Airport Link.|
|Tunisia||Northern part of the network|
|Turkey||TCDD (Türkiye Cumhuriyeti Devlet Demiryolları) (Turkish State Railways)|
|United Arab Emirates||Rail transport in the United Arab Emirates|
|United Kingdom (Great Britain)||Entire rail network in Great Britain (but not Ireland) (since standardisation by the Railway Regulation (Gauge) Act 1846)||See also the Railway Regulation (Gauge) Act 1846|
|United States||Modern national railroad network||Although it was already in use on many other lines before 1863, the Pacific Railway Act of March 3, 1863 specified that the federally funded transcontinental railroad was to use standard gauge and helped to further popularize it among American railroads.|
|Vietnam||North of Hanoi||Includes dual gauge (standard/metre) to the PRC border.|
See also 
- The gaps in the pedestrian crossings in Pompeii could give credence or otherwise to this statement, but no relevant studies appear to have been made.
- GE/GN8573, "Guidance on Gauging", Railway Group Guidance Note (London: Rail Safety and Standards Board), October 2004, retrieved 29 January 2012
- "STANDARD RAILWAY GAUGE.". Townsville Daily Bulletin (Qld. : 1885-1954) (Qld.: National Library of Australia). 5 October 1937. p. 12. Retrieved 3 June 2011.
- "Urban Legends Reference Pages: Railroad Gauges and Roman Chariots". Snopes.
- baxter 1966, p. 56
- Chaldron wagons
- Vaughan, A. (1997). Railwaymen, Politics and Money. London: John Murray. ISBN 0-7195-5150-1.
- (Whishaw 1842, p. 54)
- Whishaw (1842). p 91
- Whishaw (1842). p 260
- Whishaw (1842). p 273
- Whishaw (1842). p 303
- Whishaw (1842). p 319
- Whishaw (1842). p 363
- "TRANS-AUSTRALIAN RAILWAY. BILL BEFORE THE SENATE.". Western Mail (Perth, WA : 1885 - 1954) (Perth, WA: National Library of Australia). 2 December 1911. p. 17. Retrieved 15 March 2013.
- Jones, Stephen K. (2009). Brunel in South Wales. II: Communications and Coal. Stroud: The History Press. p. 64–65. ISBN 9780752449128.
- "The Narrow-Gauge Question". The Argus (Melbourne: Trove.nla.gov.au). October 2, 1872. Retrieved April 14, 2012.
- "ALL Mesopotamica". Railroad Development Corporation. 2007. Retrieved 2007-11-29.
- Sofia Underground
- Sofia Tramway system
- Allen, Geoffrey Freeman, Jane's World Railways, 1987-88, Jane's Information Group, 1987 (ISBN 9780710608482)
- "標準軌". ja.wikipedia (in Japanese). 2007-10-19. Retrieved 2007-11-29.
- "Mexlist". 2007. Retrieved 2007-11-29.
- "Ferrocarril Central Andino". Railroad Development Corporation. 2007. Retrieved 2007-11-29.
- "Pacific Railroad Act - Transcontiental Railroad and Land Grants". Retrieved 2008-12-25.
- "Railway Infrastructure". Vietnam Railways. 2005. Retrieved 2007-11-29.
- Baxter, Bertran (1966). Stone blocks and iron rails (Tramroads). Industrial Archaeology of the British Isles. Newton Abbot: David & Charles.
- Whishaw, Francis (1842). The Railways of Great Britain and Ireland: practically described and illustrated. London: John Weale. Republished 1969, David & Charles reprints: Newton Abbot. ISBN 0-7153-4786-1.
Further reading 
- Pomeranz, Kenneth and Steven Topik (1999). The World That Trade Created: Society, Culture, and World Economy, 1400 to the Present. Armonk, NY: M.E. Sharpe. ISBN 0-7656-0250-4.
- Puffert, Douglas J. (2009). Tracks across Continents, Paths through History: The Economic Dynamics of Standardization in Railway Gauge. University of Chicago Press. ISBN 978-0-226-68509-0.
- "The Sydney Morning Herald.". The Sydney Morning Herald (NSW : 1842 - 1954) (NSW: National Library of Australia). 23 May 1892. p. 4. Retrieved 14 August 2011., A discussion of gauge in Australia, c.1892
- A learned text of standardisation of gauge
- HOW HUNDREDS OF INCOMPATIBLE RAILROADS BECAME A NATIONAL SYSTEM