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A dual gauge railway is a track that allows the passage of trains of two different track gauges. It is sometimes called a "mixed gauge" track. A dual gauge track consists of three rails. There will be two vital rails ("gauge" rails), one for each gauge close together and a third rail, a "common" rail further away. Sometimes, four rails are required using two outer and two inner rails to create the dual gauge. Dual gauge is not to be confused with a "third rail" (the electric current traction rail) or "check or guard rails".

Background

Rail gauge, the distance between the inner surfaces of the heads of travel rails, is an important specification of a railway. Rail tracks and wheel bogies must be built to the same gauge within an engineering tolerance of . If the correct gauge is not achieved, the train will fall off the track and not be able to pass switches and crossovers. Dual gauge trains can use low level platforms because their carriages rest higher than the platform. In the case of three rails and high platforms, one gauge may be too close or too far away, depending on the position of the common rail. Another option at platforms is to construct separate tracks, one for each gauge.

Tolerance

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.

Break of gauge

"Break of gauge" occurs when rails of different gauges outside the normal tolerance meet. Passengers and freight must transfer between trains, or rolling stock must be lifted and the bogies refitted for the new gauge, or else trains with variable gauge, such as the Talgo trains commuting between Spanish Iberian gauge and French standard gauge, may pass from one gauge to the other over an appropriately designed length of track. Avoiding break of gauge reduces costs and allows infrastructure such as platforms, bridges and tunnels to be shared.

Gauge conversion

Railway operators may change from one gauge to another via a period of dual gauge operations. For example, the Great Western Railway (GWR) made a conversion from a 7-foot broad gauge to the standard gauge via a period of dual gauge operations across its network. New GWR rolling stock and locomotives of that time were built to accommodate the change. Where rails are too light for the loads of broader-gauge railcars, dual gauge rails may not be feasible. In this case, heavier rails are installed.

Configurations

thumb|Cross-sections of flat-bottomed rail which can rest directly on the sleepers, and bullhead rails which sit in chairs (not shown) One common running rail and two other outer rails provide a dual gauge. In dual gauge lines, railroad switches (points) are more complex. Trains must be safely signalled on both of the gauges. Track circuits and mechanical interlocking must also operate on both gauges. Another feature is that the wear and tear of the common rail is greater than the two other outer rails.

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. This is to ensure there is room for rail fastening hardware such as spikes and clips. File:Spurweiten Dreischienengleis.png|Three rail track This does not work for (gauge 1) and (gauge 2)
nor does it work for (gauge 1) and (gauge 2) Image:Dual Gauge Africa 3 Rail Impossible.jpg| and gauges are too close to allow 3-rail dual gauge
Functional pairing of gauges include: and ; and ; and and . and can also be dual gauged, albeit with lighter, narrow footed rails. An example of this type of pairing is seen in Victoria, Australia. File:Wallaroo-dual-gauge-railway-0855.jpg|Three rail dual gauge, and , in South Australia. File:Huesca carril.jpg|Dual gauge,
and , track between Tardienta and Ciudad de Huesca, Spain Image:Mixed-gauge-trackwork-north-geelong.jpg|Dual and
track at North Geelong, Victoria. Image:DualgaugeHakonetozanJP14.jpg|Mixed gauge track and pointwork to the left
( and
) at Odawara File:Liberec, Tatranská, výhybka u vozovny.jpg|Dual gauge tramway track in Liberec in the Czech Republic File:Hanoi Dong Dang Railway - Mapillary (6JD4MfqJ Slg2dE-uWRN Q).jpg|Hanoi–Đồng Đăng railway

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 co-location of track centres of the two gauges is needed. This might occur in tight tunnels or past platforms. 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. File:GaugeStandardMetreCentre.svg|Arrangement of rails on Chemin de Fer de la Baie de Somme Image:Dual Gauge Africa 4 Rail 2 Gauge.jpg|1000 mm and 1067 mm gauges can be combined as a 4 rail dual gauge, 1267 mm useless Image:Dual Gauge Africa 4 Rail 3 Gauge.jpg|1000 mm and 1067 mm gauges can be combined as a 4 rail dual gauge with bonus 1435 mm gauge Image:Africa four rail triple gauge.svg|Proposal for Africa - a four-rail system to support triple gauge (, , and ), thus allowing system unification in Africa. File:Haparanda-Tornio rail bridge Sep2008.jpg|1524 mm and standard gauge on a bridge across the Torne River between Haparanda (Sweden) and Tornio (Finland) File:CFBS track.jpg|A metre gauge point within standard gauge track, Chemin de Fer de la Baie de Somme, France File:Double écartement CFBS.jpg|Four rail track with a complicated switch on the Chemin de Fer de la Baie de Somme. File:Rail Baltica Lietuva.jpg|Mixed 1520 and 1435 mm gauge gauntlet track on Lithuanian part of Rail Baltica line between Mockava and Šeštokai File:CFBS Avant gare de Noyelles.JPG|Approaching Noyelles-sur-Mer. Note the metre gauge track laid within the standard gauge File:巡道工出品 Photo by Xundaogong 绥芬河印象 - panoramio.jpg|Mixed gauge track at Suifenhe Railway Station near the China-Russia border

Triple gauge

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. Thus, if required, light rail could be used to space the rails closely together. Light rail was not used at the Niagara Falls Suspension Bridge and it would not be used for main line operation at high speeds.

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. The National Railway Museum, Port Adelaide in Adelaide, Australia has the three main-line gauges and a gauge Heritage railway line. 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 did include a turnout splitting a standard gauge track from the seven-rail track. It required eight frogs in a row. File:Quadruple gauge rail tracks at Alan Keef works.jpg|Quadruple gauge rail tracks at the Alan Keef locomotive works at Lea, Herefordshire in the United Kingdom. File:Triple Gauge Australia.jpg|Triple gauge used in the station yards at Gladstone and Peterborough in South Australia File:CRW 1138.jpg|The Steamtown Heritage Rail Centre turntable, with its three rail gauges File:Cross-section of Australian triple-gauge track.png|Cross-section of triple-gauge track at Gladstone and Peterborough, South Australia, before gauge standardisation in 1970 (click to enlarge) File:Different gauges in China Railway Museum.jpg|Different gauges, from left: , , and , on display at the China Railway Museum in Beijing

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 gauge

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).

Other procedures

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 a different gauge. This system is not suitable for four-wheeled wagons. 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.

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 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. When 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 600 mm 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 (21,7 km). 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 Jenny, 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. 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.The length of Vietnam railway network

Dual gauge galleries

Jindřichův Hradec, Czech Republic, using the narrower gauge. As seen in the foreground, it does not use the outer rail Image:RhB dual-gauge track.jpg|Sunlight reflects off
and
dual gauge tracks near Chur, Switzerland Image:Narrow gauge (tram Katwijk).JPG|Previously used
and
dual gauge tram tracks in Katwijk, Netherlands File:Treskensväxel vid Jenny.jpg|In Jenny, Sweden, the narrow gauge leaves the standard gauge Image:Stuttgart dt8.jpg|Two class DT-8 Stuttgart Stadtbahn cars on dual gauge track in Stuttgart, Germany Image:Switch-bifurcation of dual gauge rail near Jindrichuv Hradec.jpg|Bifurcation of dual gauge track near Jindřichův Hradec, Czech Republic using a switch File:VFDWiki8.jpg|Residual dual gauge track on the Voies Ferrées du Dauphiné in France. File:Mixed gauge track Didcot.JPG|Reconstructed mixed-gauge,
/
track at Didcot Railway Centre, England File:Broad Gauge mixed gauge track, Didcot Railway Centre, Oxfordshire.jpg|Broad Gauge mixed gauge track,
/
Didcot Railway Centre File:Baulk road point with side step.jpg|alt=A rail track recedes into the distance where a steam train stands; the track has three rails, the middle of which is offset to the right in the foreground but switches to the left in the middle at some complex pointwork where three other rails join from the left|A train on dual gauge track, Didcot Railway Centre File:Schema rollbocks trucks.PNG|Rollbocks compared to transporter wagons
File:Cusco vía férrea y avenida del ejército.jpg|Dual gauge, and track in Cuzco, Peru. File:PostcardMesaGrandeCARailroadStationCirca1910.jpg|Mesa Grande station was served by dual-gauge, and track. File:Dual gauge railroad.jpg|Dual gauge railroad, & ,
at Belo Horizonte, Brazil.
Image:Avonlink Bellevue.jpg|''Avonlink set'' going on dual gauge track under the Great Eastern Highway bridge in Swan View in October 2009 Image:Dualgaugedevice.jpg|Dual gauge track in Melbourne, Victoria. Note guard rails which force standard-gauge trains to change side. Image:Indian Pacific Perth, Western Australia.jpg|Dual gauge track in Perth, Western Australia. Narrow gauge train on left; Standard gauge train on right.
Tracks are separating for island platform used only by narrow gauge electric trains. Image:Set47.jpg|A2 Set 47 accelerates out of Success Hill en route to Midland on dual gauge track. Image:Prospector_new_railcar,_Toodyay.jpg|''The Prospector'', on dual gauge track, near Toodyay in February 2004

* Broad-gauge railway * Dual Gauge feasibility * Gauntlet track * Glossary of rail transport terms * History of rail transport * Quadruple-track railway * Rail transport * Rail transport by country * Tamping machines

References