Dual gauge
A dual gauge railway line has track consisting of two rails spaced according to one track gauge, to which are added either one or two more rails spaced according to another track gauge. Since tracks of two gauges are more expensive to configure with signals and sidings, and to maintain, than two separate single-gauge tracks, it is usual to build dual-gauge tracks only when necessitated by lack of space. An alternative term for dual gauge is "mixed gauge". Triple gauge (which is much less common than dual gauge) is also termed "multiple gauge" or "multi-gauge . Background. Rail gauge – the distance between the inner surfaces of the heads of the rails – is a fundamental specification of a railway. Rail tracks and wheelsets are built within engineering tolerances that allow optimum lateral movement of the wheelsets between the rails. Rails that become too wide or narrow in gauge will cause derailments, especially on curves. Configurations. Dual-gauge track can consist of three rails, sharing one common" rail; or four rails, with the rails of the narrower gauge lying between those of the broader gauge. In the three-rail configuration, wear and tear of the common rail is  greater than with the two other outer rails. In dual gauge lines, railroad switches (points) are more complex than in single-gauge track, and trains must be safely signalled on both of the gauges. Track circuits and mechanical interlocking must also operate on both gauges. Three rails. Dual-gauge track with three rails must provide a difference between the gauges at least as wide as the feet of the two outer rails to ensure there is room for rail fastening hardware such as spikes and clips. Functional pairing of gauges includes: and can also be dual-gauged; examples can be  seen in Australia, especially where new standard-gauge track has been laid on the same route as older broad-gauge tracks that must be retained, but space in the corridor is insufficient for it to be laid independently of the broad-gauge track. Four rails. Gauges which are too close to function in a three-rail arrangement include and (common in Africa); and (common in South America); and and , and and . The last combination is common in Afghanistan, Central Asia, northern, central and eastern Europe, Russia, North America, Iran, and China. In Europe, it was of strategic importance in World  War II. In these cases, a gauntlet track which uses four rails is constructed. An example of this is seen at the Rail Baltica project which aims to connect central and northern Europe by rail. Four rails may also be used where a collocation of track centres of the two gauges is needed. This might occur in tight tunnels or past platforms, or for equipment turntables. An example is seen at the Roma Street railway station in Brisbane, Queensland, Australia. There, both three-rail and four-rail dual-gauge systems are used between and gauges. Triple gauge. Tracks holding rolling  stock at the National Railway Museum, Port Adelaide are built to the three Australian mainline gauges – , and – and a gauge passenger-carrying line. Break of gauge occurs at some triple gauge stations. In the examples below, the triple gauge was used in rail yards where trains operate at low speeds. Quadruple gauge. Within a works facility or maintenance yard, tracks consisting of four or more separate gauges may be used. At Alan Keef in Lea, Herefordshire a short section of line uses four rails to allow locomotives of , , and gauges to enter the works. In the 1960s and 1970s, the  Electro-motive diesel (EMD) plant in McCook, Illinois maintained a small amount of multi-gauge track with up to seven parallel rails in order to support the wide variety of export locomotives they produced. This track included a turnout splitting a standard gauge track from the seven-rail track. It required eight frogs in a row. Switches. Dual-gauge switches (also known as "turnouts" or "points"), where both gauges have a choice of routes, are more complicated than those where two gauges separate or single gauge switches. The train must move through a dual gauge switch very slowly. The ends  of dual gauge switches are easier to design if their operation is electrical rather than mechanical. If two gauges are similar in width, the switch they use will have many small pieces that are difficult to support. The switch will also be limited in speed. The difference between the gauges should be 50 mm greater than the width of the base of the rails. In a rail yard, weak dual gauge switches are avoided by separating the gauges and using, single gauge switches, and dual gauge diamond crossings. Gauge splitters are used for trains of a single gauge. The fixed  type have no moving parts and trains move through them slowly. Power operated gauge splitters are operated like ordinary switches. Other configurations. Separate gauges. Dual gauge lines are separated by building two tracks, one of each gauge, side by side. Whether a dual gauge line remains depends on the volume of rail traffic it carries and also its location, for example across a bridge or through a tunnel. Separated lines share infrastructure such as signal boxes and signallers. In Victoria (Australia), on the Melbourne to Geelong line , a single line runs parallel to the double track . Prior to 1941, the  Yogyakarta Surakarta line in Java, in the Dutch East Indies, had a single line in parallel with a dual gauge and a line. In 1960, in Western Australia, the Perth to Northam line was to be a narrow gauge track running in parallel with a line. Planners then realised a double dual gauge line would increase capacity. The Uzhhorod–Košice broad-gauge track in Slovakia runs in parallel to a double track line. Overlapping gauges. Flat crossing Railway of one gauge may be extended into territory that uses another gauge. This may avoid transhipment. For example, a gauge line runs  from an iron ore mine in Ukraine to a steelworks in Slovakia. A portion of four rail dual gauge line (1435 mm and 1520 mm) runs from Slovakia to Romania (both standard gauge) through Ukraine (Russian gauge). Transporters, bogie exchange and adjustable wheels. Transporter wagons, transporter trucks, and rollbocks are used to carry vehicles built for one gauge on a line with a different gauge. They can manage a trainload at a time. Bridges and tunnels must be one metre higher than usual. Bogie exchange systems lift the railroad car while trucks or bogies are changed for ones of a  different gauge. In the case of four-wheeled, two axle, railroad cars the two wheelsets may be exchanged, provided that the brakes can be adjusted. The Ramsey car transfer apparatus is another way to change bogies. Adjustable gauge equipment or variable gauge axles, allow a wheel gauge to be altered. Transshipment procedures move containers and people from one train to another. Operation with very small gauge differences. If the difference between two rail gauges is small enough, i.e. within each other's tolerances, then it is possible for them to operate the same rolling stock. At the FinlandRussian border the  Finnish railway gauge is and the Russian gauge is . When the Soviet Union changed the gauge of its railways in Russia in the 1970s to , this did not result in a break of gauge and no track conversion work was done. The change in gauge was a redefinition of the way tolerances were measured. Both railways remained well within each other's tolerance and can run the same rolling stock. However, being within a tolerance in gauge does not always mean that two different system can successfully operate the same rolling stock. For example, the MTR (Mass Transit Railway) in  Hong Kong Electric multiple units (EMU) may run on Kowloon-Canton Railway (KCR) tracks but would need a locomotive or a KCR EMU pulling due to the difference in electrification voltages. Dual voltage and frequency EMUs are the other solution. Model railways / miniature ridable railways. Tillig makes dual gauge model railway track. Many ridable miniature railways utilise dual gauge, often with models of the same prototype built to different scales to match the gauge. Dual gauge railways by nation. Selected examples in alphabetical order. Australia. In Victoria, there are sections of and dual gauge track between Southern Cross station and  West Footscray, Sunshine and Newport, Albion and Jacana, North Geelong and Gheringhap, Maryborough and Dunolly, and in various goods yards and industrial sidings. Until 2008, there was dual gauge line between Wodonga and Bandiana. At Albury railway station, New South Wales there was and dual gauge line until 2011. There is dual gauge within Tocumwal railway station but in 1988, the standard gauge component was put out of use. In 1900, in Western Australia, the three rail dual gauge system was proposed in order to avoid a break of gauge. However, designing switches was initially said to be difficult due  to the distance of between the and the Victorian broad gauge (). After twenty years of discord, the dual gauge proposal and the Brennan dual gauge switch were abandoned. Much later, the Australian Rail Track Corporation (ARTC) did successfully adopt dual gauge switches. In Western Australia, there is a and ) double track dual gauge running over of the main line from East Perth to Northam. Dual gauge track is also used from the triangle at Woodbridge to Cockburn Junction, then to Kwinana on one branch, and North Fremantle on the other. The signalling system detects the gauge of the approaching train  and puts the signals to stop if the route is set for the wrong gauge. This is easier to do if the signalling is electrical rather than mechanical. In Queensland, there is a section of dual gauge track and dual gauge tacke between the rail freight yards at Acacia Ridge and Park Road Station which is utilised by both passenger and freight trains. Freight trains to the Port of Brisbane utilise the dual gauge Fisherman Islands line that runs parallel to the Cleveland railway line from Park Road to Lindum. Passenger trains utilise the dual gauge section of the Beenleigh  railway line running parallel to the electric suburban narrow gauge of the Queensland Rail City network line over the Merivale Bridge into Platforms 2 and 3 at Roma Street Station. This is used by standard gauge interstate NSW TrainLink XPT services to Sydney. In 2012, a dual gauge line was installed between Acacia Ridge and Bromelton to serve a new freight hub at Bromelton. The long Inland Railway (under construction in 2020) has about of dual gauge. Bangladesh. Bangladesh Railway is using three rails to avoid break of gauge with its broad and meter gauge lines. The new Jamuna Bridge  that links the east and west rail systems is a four rail dual gauge line. Belgium. Tram tracks in Brussels once combined lines for inter-urban trams and lines for urban trams in a three-rail layout. Once the inter-urban trams went out of service, the network used only standard gauge track. Bulgaria. The Sofia tramway uses a mixture of narrow and standard gauge. A section of track between Krasna polyana depot and Pirotska street is dual gauge shared by route 22 and narrow gauge route 11. Czech Republic. In the Czech Republic, there is 2 km of dual  gauge ( and ) track near Jindřichův Hradec. In 1985, its original four rails were converted to three rails. On September 9, 2004, in Jindřichův Hradec at a switch where a dual gauge railway bifurcates, a Junák express from Plzeň to Brno derailed due to a signalling error. The standard gauge train had been switched onto the narrow gauge track. The express train driver was slightly injured. France. The Chemin de Fer de la Baie de Somme in France is dual gauge between Noyelles-sur-Mer and Saint-Valery-sur-Somme. The line has four rails with metre gauge laid within standard  gauge. Germany. In the 1970s, the Stuttgarter Straßenbahnen tram lines underwent a gauge conversion from gauge to standard gauge. This was part of an upgrade to the Stuttgart Stadtbahn. In 1981, and dual gauge track was constructed so that new DT-8 Stadtbahn cars and old trams could share the network. In 2008, a further gauge conversion was completed. The Stuttgart Straßenbahn Museum operates gauge trams on weekends and special occasions. In Krefeld on Ostwall, Germany, tram lines are dual gauge so standard Rheinbahn U76 Stadtbahn cars and gauge trams may share the lines. At the north end of the route , at the junction with Rheinstraße, the trams reverse. There, the standard gauge line ends, while the metre gauge lines continue. At the Hauptbahnhof, on Oppumer Straße dual gauge track continues. At the ends of Oppumer Straße, the and standard tracks diverge. In Mülheim there is a similar situation. The Duisburg tram line 901 meets the local line 102. The tram system in Duisburg uses gauge track while the tram route from Witten to Mülheim uses gauge tracks. Lines 901 and 102 share a tunnel section between the Mülheim (Ruhr) Hauptbahnhof and Schloss Broich. The lines diverge at street level. The  tram network between Werne to Bad Honnef is large with various operators and gauges. The trams in Wuppertal used gauge track on eastwest lines and gauge track on northsouth lines. Trams in Duisburg used gauge track on lines south of the Ruhr and gauge tracks on lines north of the Ruhr. The north lines closed in the 1960s and 1970s. Duisburg's three routes were converted to gauge track. Ghana. Ghana is converting its narrow gauge to standard gauge, and is installing dual gauge sleepers as an intermediate stage. Greece. In Greece, the line between Athens and Elefsis (now closed ) was dual gauge in order to allow the gauge trains of the Peloponnese rail network to pass. It also allowed standard gauge trains to reach the Elefsis shipyards. In Volos, a short section of track between the main station and the harbour used an unusual triple gauge, to accommodate standard gauge trains from Larissa, metre gauge trains from Kalambaka, and the gauge trains of the Pelion railway. Indonesia. In 1899, in the Dutch East Indies, dual gauge track was installed between Yogyakarta and Solo. The track was owned by the Nederlandsch-Indische Spoorweg Maatschappij, a private company, which in 1867  had built the gauge line. The third rail was installed to allow passengers and goods traveling over the gauge "Staatsspoorweg" (state railway) a direct connection. At a later date, the government constructed new tracks to allow greater capacity and higher speeds. In 1940, a third rail was installed between Solo and Gundih on the line to Semarang, allowing gauge trains to travel between Semarang, Solo and Yogyakarta via Gambringan, on the line to Surabaya instead of on the original line via Kedungjati. In 1942 and 1943 in Java, under Japanese rule, conversion from took place to on the BrumbungKedungjatiGundih main  line and the KedungjatiAmbarawa branch line. Until the 1970s, a short section of dual gauge and line existed in North Sumatra on a joint line of the Deli Railway and the Atjeh Tram. Some sugar mill railways in Java have dual gauge sections. Ireland. Ireland's Ulster Railway underwent a gauge conversion from to the new Irish standard of . The Dublin & Drogheda Railway underwent a gauge conversion from . This and the new Irish standard were too close to allow a dual gauge line. Italy. The Potenza Avigliano Lucania line in Italy is a dual gauge rail with and tracks. Japan . In Japan, the national railway standard is the narrow gauge track. Dual gauge is used where the Shinkansen (bullet train) lines join the main network. For example, part of the Ōu Main Line became part of the Akita Shinkansen and was converted to dual gauge in a limited section. The longest () dual gauge section in Japan is around and in the Seikan Tunnel. Mexico. Mexico previously had and dual gauge track. Netherlands. The first railway lines in the Netherlands were constructed with a track gauge of . For the 1939 centennial celebration, an exact replica of the country's first locomotive  De Arend was built using the original blueprints. Since 1953, the locomotive is housed at the Dutch National Railway Museum, where in recent years, a dual gauge track has been constructed in the rail yard, allowing for De Arend to drive back and forth on special occasions. Poland. In Poland, there is a 3 km and dual gauge section in the Greater Poland Voivodeship, linking Pleszew with a nearby mainline station. It is served by narrow gauge passenger trains and standard gauge freight trains. Russia. Between October 2008 and February 2012, a cross border stretch of track between Russia and  North Korea was rebuilt. It is a dual gauge line with and tracks between Khasan in Russia and Rajin in North Korea. Spain. In Spain, there is dual gauge in the AVE line from Zaragoza to Huesca, usable for both standard gauge high speed trains and Iberian gauge Spanish trains (). In 2009, Adif called for tenders for the installation of a third rail for standard gauge trains on the between Castellbisbal and the Can Tunis freight terminal in Barcelona. Sweden. The bridges at the borders of Sweden and Finland, between Haparanda and Tornio have of dual gauge, and track. At  each end of the dual-gauge section there are yards with standard and Finnish gauge areas to allow for transshipment. The four-rail method is used because the gauges are close. The bridge structure is wide to allow for the offset from the centreline of each gauge. There is a Rafil gauge changer at the Tornio yard. Similar arrangements exist on the approach to Kaliningrad, where track penetrates from the Polish border with some dual gauge stretches. Between Västervik and , in Sweden there is a and dual gauge line and a dual gauge track in the Västervik station area. Switzerland . In Switzerland, dual gauge standard track and metre track is used in Lucerne and Interlaken stations, the terminals of the Brünigbahn. A section of dual gauge at Niederbipp allows the Jura Foot Railway and the Oberaargau-Jura Railways to share the station there. The RhB line between Chur and Domat/Ems is also dual gauge. United Kingdom. The Great Western Railway in Britain was originally a broad gauge line. After a "gauge war", a track gauge conversion was made. A dual gauge system was easily installed as the gauges were well separated and the line had wooden sleepers. A short  section of broad gauge and remains at the Great Western Society site at Didcot as a demonstration line. The port authority in Derry, Northern Ireland uses a dual gauge line in a street level network to transfer freight. Two of the city's stations are on a narrow gauge. The other two city stations are on broad gauge. United States. In Los Angeles, the previously operating Los Angeles Railway and Pacific Electric Railway ran on dual gauge track on some downtown streets. From 1880 to 1902, the Burlington, Cedar Rapids and Northern Railway (standard gauge) and the Burlington and Northwestern  Railway (narrow gauge) shared a dual gauge mainline from Burlington, Iowa to Mediapolis, to the north. The early operational years of the State Belt Railroad in San Francisco featured dual gauge tracks to accommodate regional railroads of the time, which interchanged via ferry. Until 1941, the Colorado and Southern Railway used both standard and narrow gauge tracks, and had a dual gauge line between Denver and Golden, Colorado. Until the 1960s, the Denver and Rio Grande Western Railroad's Alamosa–Durango Line from Alamosa, Colorado to Antonito was dual gauge. Previously, in its Mount Union, Pennsylvania yard, the East Broad  Top Railroad and Coal Company used dual gauge tracks. Apart from the Los Angeles Railway and the Pacific Electric Railway, the examples were and Vietnam. In Vietnam, near the border with China, there is and dual gauge track between Hanoi and Đồng Đăng. Other smaller dual gauge sections exist elsewhere in the northeast of the country.