Track gauge
By transport mode
By size (list)
Graphic list of track gauges

Minimum
  Minimum
  Fifteen inch 381 mm (15 in)

Narrow
 
  • 600 mm
  • 610 mm
  • 686 mm
  • (1 ft 11+58 in)
  • (2 ft)
  • (2 ft 3 in)
 
  • 750 mm
  • 760 mm
  • 762 mm
  • (2 ft 5+12 in)
  • (2 ft 5+1516 in)
  • (2 ft 6 in)
 
  • 891 mm
  • 900 mm
  • 914 mm
  • 950 mm
  • (2 ft 11+332 in)
  • (2 ft 11+716 in)
  • (3 ft)
  • (3 ft1+1332 in)
  Metre 1,000 mm (3 ft 3+38 in)
  Three foot six inch 1,067 mm (3 ft 6 in)
  Four foot 1,219 mm (4 ft)
  Four foot six inch 1,372 mm (4 ft 6 in)
  1432 mm 1,432 mm (4 ft 8+38 in)

  Standard 1,435 mm (4 ft 8+12 in)

Broad
 
  • 1,445 mm
  • 1,450 mm
  • (4 ft 8+78 in)
  • (4 ft 9+332 in)
  Leipzig gauge 1,458 mm (4 ft 9+1332 in)
  Toronto gauge 1,495 mm (4 ft 10+78 in)
 
  • 1,520 mm
  • 1,524 mm
  • (4 ft 11+2732 in)
  • (5 ft)
 
  • 1,581 mm
  • 1,588 mm
  • 1,600 mm
  • (5 ft 2+14 in)
  • (5 ft 2+12 in)
  • (5 ft 3 in)
  Baltimore gauge 1,638 mm (5 ft 4+12 in)
 
  • 1,668 mm
  • 1,676 mm
  • (5 ft 5+2132 in)
  • (5 ft 6 in)
  Six foot 1,829 mm (6 ft)
  Brunel 2,140 mm (7 ft 14 in)
Change of gauge
By location
World map, rail gauge by region
Sunlight reflects off dual-gauge tracks near Chur, Switzerland
Mixed-gauge track and pointwork (4 ft 8+12 in (1,435 mm) and 42) at Odawara in Japan
Dual-gauge tram tracks in Katwijk, The Netherlands

Dual-gauge or mixed-gauge railway is a special configuration of railway track, allowing trains of different gauges to use the same track. Generally dual-gauge railway consists of three rails, rather than the standard two rails. The two outer rails give the wider gauge, while one of the outer rails and the inner rail give a narrower gauge. Thus one of the three rails is common to all traffic. (This configuration is not to be confused with the electric third-rail.)

Reasoning

In railways, the most important specification is that of gauge: the distance between the inner surfaces of the heads of the travel rails (see diagram). Both track and wheels (trucks, bogies) must be built to the same gauge; unless the two fit together perfectly (within a tolerance of a few millimetres), the train will fall off the track. A problem arises when different systems, with different gauges, meet one another (a situation known as a break of gauge). Either the track or the train must be built to handle different gauges, or all of the passengers and freight must be taken off one train and loaded on to the next.

In allowing railway tracks of different gauges to share the same alignment, costs can be reduced, especially where there are bridges and tunnels. Dual-gauge can replace two separate tracks, having two rails each, with one track with three rails. This allows one rail fewer for the stretch of the dual gauge line, but there are complications and costs that may offset the savings.

One issue is points (US: switches). Complicated arrangements are necessary to ensure traffic of both gauges can safely utilise points. Signalling may also be complicated somewhat, as all three rails must be connected to track circuits or mechanical interlocking arrangements. Mixed gauge is simpler to signal with electric signals than with mechanical signals. Since rails wear very slowly, the extra tonnage on the common rail is not a problem.

Dual-gauge turnouts will be complicated, expensive, and suitable for low speeds only.

Configuration

For dual-gauge track to be achievable using three rails, the difference between the gauges needs to be at least as wide as the foot of the rail, otherwise there is no room for the rail fastening hardware (spikes, clips, and the like). Thus standard gauge (1435) and Indian gauge 1676 can be dual gauged without problem, while 1435 and 1600 (Irish gauge) can also be dual-gauged, albeit with lighter narrow footed rails, as shown in Victoria, Australia. On the other hand, metre gauge 1 and cape gauge 1067 as found in Africa, or 1 and 36, as found in South America, are too close to be combined into three-rail dual gauge, as are 1435 and 1524.

If three-rail dual gauge is impossible, four-rail dual gauge has to be used.

Configuration for Africa

Standard gauge (4 ft 8+12 in (1,435 mm)) and 42 gauge (as found in Africa) are sufficiently dissimilar to allow three-rail dual gauge track.
Proposal for Africa - a four rail system to support triple gauge (1435, 1, and 1067), thus allowing system unification in Africa.

1067 and 1 gauges found in Africa are too close to allow three-rail dual gauge: four-rail dual gauge is required. With a little care, the sleepers for this dual gauge configuration can be made to support triple gauge, including standard gauge (1435), at little extra cost. Additional gauges for this configuration are 368 mm, 435 mm and 632 mm.

An advantage of the four-rail dual gauge track is that the four rails can be combined to give some of the greater strength of two rails of double the weight. This allows the old rails to be reused, instead of being scrapped or used for low-value fenceposts. [1]

Example in Africa

2007

2006

An Indian proposal surfaced to link Benin and Togo on the coast with landlocked Burkina Faso and Niger. The other adjacent state of Ghana and Nigeria use the incompatible 1067 mm gauge. With the future in mind, steel and concrete sleepers, at least between stations, can and should cater for three gauges, 1000 mm, 1067 mm and 1435 mm.

2004

On 12 October 2004, a proposal was announced to develop an electrified rail link connecting Kenya, Uganda and south Sudan. Even though Kenya and Uganda use 1000 mm gauge and Sudan uses 1067 mm, the new project was proposing to use standard gauge (1435 mm). Fortunately, all three gauges can be supported by the same sleepers, as described above.

Gauge conversion

This locomotive was derailed by the 1906 San Francisco earthquake. The locomotive had three link and pin coupler pockets for moving standard and narrow gauge cars.

The complications and difficulties outlined show how important it is to ensure that railway gauges are standardised in the first place, if at all possible. If a railway operator seeks to convert from one gauge to another, then it helps if a dual-gauge intermediate step can be done (this has often been actually practised in the past).

If the gauge is to be reduced, then the sleepers can continue to protrude from the side of the rails. If the gauge is to be increased, then the sleepers used for narrow gauge may be too short, and some at least of these 'short' sleepers will have to be replaced with longer ones. Alternatively the rails may be too light for the loads imposed by broader-gauge railcars. Such potential problems can rule out dual-gauge as a feasible option. Another issue is affixing the rails to the sleepers (spikes, nails or bolts are used). If existing sleepers are wooden, extra holes can be drilled without problems. If the existing sleepers are concrete, then drilling extra holes is impractical, and the whole sleeper has to be replaced, unless extra boltholes are already allowed for.

The embankment could need wideing too. It is possible that viaducts and tunnels are too narrow and too low. This could cost a lot and need the closing of the line for a year or two.

During the conversion of the Melbourne to Adelaide line in Australia from 63 to 4 ft 8+12 in (1,435 mm), dual gauge with heavy rails was not possible as the rail footings were too wide. A special gauge-convertible sleeper with a reversible chair for the Pandrol clip allowed a two-week conversion process.

In the Adelaide metropolitan area, broad-gauge timber sleepers are being replaced with gauge-convertible concrete sleepers. On June 5th, 2008, the South Australian Government announced that the Metropolitan Network would be converted to Standard Gauge (1435mm) in 2012.[2]

The dual-gauge lines in Java were regauged to Cape gauge (4 ft 8+12 in (1,435 mm) to 42) during the Japanese administration in 1942-1943. Actual regauging only occurred on the relatively short Brumbung-Kedungjati-Gundih main line and the Kedungjati-Ambarawa branch line, as the rest of the line was already dual-gauge (some only recently dual-gauged).

Proposed or current gauge conversions

Cost of examples

Examples

A train running on mixed-gauge track near Jindřichův Hradec, Czech Republic, using the narrower gauge – not running on the outer rail, seen in the foreground.

In the Czech Republic, there is dual gauge (1435 mm and 760 mm) track near Jindřichův Hradec. Interestingly, the two gauges are used by different railway companies.

In Britain, the Great Western Railway was initially broad gauge. After the "gauge war", it was decided to regauge the GWR. As the broad gauge was sufficiently dissimilar from standard gauge and used wooden sleepers, dual gauge was easily introduced for running new standard-gauge traffic. The Metropolitan Railway, part of the London Underground system, also started out as dual-gauge; however, its current third and fourth rails are for electricity supply, not dual gauge.

In Ireland, dual-gauge track was not used in regauging the Ulster Railway (UR). When it regauged its double-track route from 1880 mm (6 ft 2 in) to the new standard of 63 it performed the task in two stages. The Dublin & Drogheda Railway (D&DR) meanwhile was regauging from 1575 mm (5 ft 2 in), too similar to the new gauge to allow dual gauge. Dual gauge was used in Derry, by the Port Authority, in an on-street network to transfer goods, on either gauge, between the city's four stations (two 36 narrow gauge, two 5 ft 3 in broad gauge).

In Italy, dual-gauge track is used in the line Potenza - Avigliano Lucania (1435) and (950).

Metre gauge within standard gauge

In France, the Chemin de Fer de la Baie de Somme is dual gauge between Noyelles-sur-Mer and Saint-Valery-sur-Somme. the line being metre gauge laid within standard gauge, thus having four rails.

In Western Australia, there is a double-track dual-gauge (42 & 4 ft 8+12 in (1,435 mm)) main line from East Perth to Northam, about 120 km. 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.

In Brisbane, Australia, shorter stretches of dual-gauge track (42 & 4 ft 8+12 in (1,435 mm)) exist between the rail freight yards at Acacia Ridge and the Port of Brisbane for freight trains. A dual-gauge line branches off at Park Road Station to run alongside electric suburban narrow gauge Citytrain services over the Merivale Bridge into Platform 1 at Roma Street Station. This is used by standard-gauge interstate CountryLink XPT services to Sydney.

Two class DT-8 Stadtbahn cars on dual-gauge track in Stuttgart, Germany

In Belgium, some sections of tram track in Brussels combined metre gauge for the interurban trams with standard gauge for the urban trams. Since the closure of the former, these have been replaced with standard gauge track.

In Stuttgart, Germany, the tram lines were 1000 mm gauge. In the 1970s it was decided to convert the streetcar system to a modern Stadtbahn and regauge it to standard gauge to increase capacity. Inner-city tunnels replacing street-level sections in busy streets were built with a cross-section suitable for standard-gauge cars. After the conversion started in 1981 with the commissioning of the first three class DT-8 Stadtbahn cars, the tunnels and all other sections used by multiple lines were fitted with 1435 mm / 1000 mm dual-gauge track, to allow both old-style streetcars and new Stadtbahn cars to share those sections while lines were converted one by one over the next decades. In 2006, conversion of line 15 (the last line to be converted) is under way and expected to be complete around 2008, although some sections will retain their dual-gauge track indefinitely as a courtesy to the streetcar museum of Stuttgart, which will operate old 1000 mm gauge streetcars on weekends and special occasions.

In Switzerland dual gauge (standard and meter) is used in the stations at both ends of the Brünigbahn (Lucerne and Interlaken), as well as on the RhB between Chur and Domat Ems (see first illustration of this article), among other places.

In Japan, dual gauge is used when the Shinkansen system, which is standard gauge, joins the narrow-gauge (1067 mm) system, which is the national standard. For example, part of the Ōu line became part of the Akita Shinkansen and was upgraded to dual gauge.

In Dutch East Indies (later Indonesia), dual-gauge track was installed in 1899 between Yogyakarta and Solo. The track was owned by the Nederlandsch-Indische Spoorweg Maatschappij, a private company, which built the 4 ft 8+12 in (1,435 mm) gauge line in 1867. The third track was installed to allow passengers and goods traveling over the 42 gauge Staatsspoorweg (State Railway) a direct connection without requiring transfer at both cities. Later, a separate pair of tracks were installed at the government's cost to allow greater capacity and higher speeds.

In 1940 a third rail was installed between Solo and Gundih on the line to Semarang, allowing 42 gauge trains to travel between Semarang, Solo and Yogyakarta (via Gambringan, on the line to Surabaya instead of via Kedungjati on the original line).

A short section of dual-gauge 42 and 2ft 5½in (750 mm) line existed in North Sumatra on a joint line of the Deli Railway and the Aceh Tramway. This line survived in to the 1970s.

Some sugar mill railways in Java also have dual-gauge sections.

In Vietnam, there is dual gauge (1 meter and 1435 standard) between Hanoi and the Chinese border.

The length of Vietnam railway network

In Sweden and Finland, there is about 4 km of dual gauge, 1435 and 1524 mm, between the railway stations in Haparanda and Tornio on each side of the border. The four-rail method is used because the gauges are too close.

In Los Angeles the Los Angeles Railway and the Pacific Electric Railway (both defunct) ran on dual gauge track on some downtown streets.

Double dual gauge

In Australia, the new railway line between Perth and Northam was being planned in the 1960s. The improved alignment was originally intended to have separate standard gauge and narrow gauge tracks running parallel, with crossing loops at intervals. However, the capacity of each of these lines would have been poor. By adopting double-track dual-gauge throughout, the line capacity was greatly increased, at only the relatively small extra cost of providing a third rail needed for dual gauge.

Triple gauge

There have been a few instances of triple-gauge break-of-gauge stations.

Area Gauge 1 Gauge 2 Gauge 3 Note
Port Pirie, South Australia 1067 1435 1600 1938-1970, some survives in the Peterborough Railway Museum.
Gladstone, South Australia 1067 1435 1600 1970-1980s
Peterborough, South Australia 1067 1435 1600 1970-1980s
Latour-de-Carol, France 1000 1435 1668 still in use
Hendaye, France 1000 1435 1668 still in use
Växjö, Sweden 891 1067 1435 until at least 1974
Montreux, Switzerland 800 1000 1435 still in use
Volos, Greece 600 1000 1435 not all in use

Because these three triple-gauge examples were yards operating at low speed, light rail could be used to space the rails closely together if required. Main line operation at high speeds is another matter.

The Niagara Falls Suspension Bridge originally carried trains of three different gauges.

The National Railway Museum (Port Adelaide) in Adelaide, Australia not only has the three main line gauges, but also a 1' 6" gauge tourist line.

Accidents on dual-gauge railways

Switch - bifurcation of dual-gauge track near Jindřichův Hradec, Czech Republic.

On September 9, 2004, an accident happened on a switch in Jindřichův Hradec, Czech Republic where dual-gauge railway bifurcates. An Junák express train from Plzeň to Brno derailed here because of a signalman's fault. He switched the switch to the narrow-gauge track although the express train used the standard-gauge one. Only the driver of the express train was slightly injured.

In Western Australia, the signalling system detects the gauge of the approaching trains and puts the signals to stop if the route is set for the wrong gauge.

Complexity of dual-gauge switches

Dual-gauge turnouts (also known as switches or points), where both gauges have a choice of routes, are quite complicated, with more moving parts than single-gauge turnouts. They impose very low speed limits. If dual-gauge points are operated and detected by electrical circuits, their reliability will be high.

Where two gauges separate (i.e. each gauge has only one route, as in the picture at right), few moving parts are needed.

Paradox

If the two gauges of a dual gauge turnout are very similar and the difference between them is small, then turnouts will have many small pieces that are difficult to support and the turnout will be weak and limited in speed. Paradoxically, the larger the difference the better. The difference between the gauges should as a rule of thumb be say 50mm greater than the width of the base of the rails. The three most common gauges in Africa when configured as above have relatively large differences between the gauges and the turnout will be relatively strong and its speeds will be reasonable. Conversely, the three gauges found on the borders of Afghanistan are too similar.

Gauge splitters

One way of avoiding complicated and weak dual gauge turnouts, provided there is room, is to separate the gauges and then design the yard with single gauge turnouts and dual gauge diamond crossings. [5] [6]

Separate gauge

If dual-gauge turnouts are too slow, or too difficult because the gauges are too similar, then an option is to build two separate lines, one of each gauge, side by side. This choice also depends on the amount of traffic. Dual-gauge could continue to be employed at an expensive bridge or tunnel.

Examples include:

Overlapping gauges

Bangladesh is tackling its break of gauge problem by adding a third rail to its broad and narrow gauge lines, so that it becomes a mainly dual-gauge system. The new Jamuna Bridge that links the east and west rail systems is four rail dual gauge so that both gauges use the same centre-line. At some stage in the future, Bangladesh may choose one gauge over the other and convert to a single gauge, but there are no immediate plans for this.

Bangladesh's neighbour to the east is also 1000 mm gauge, should the missing link ever be built.

A variation of overlapping gauge is to extend a railway of one gauge into territory that is mainly of another gauge so as to avoid transhipment of specific traffic. For example a 1524 mm gauge line from an iron ore mine in Ukraine to a steelworks in Slovakia which now may be extended into Austria. [7]

Other methods of handling multiple gauges

Other methods of handling multiple gauges include:

Dual gauge dual voltage

A mini-metro in Gijon, Spain is to be both dual gauge (1000 mm/1668 mm) and dual voltage (1500 V DC/3000 V DC).

See also

References

  1. ^ RailwaysAfrica
  2. ^ "Rail Revitalisation". South Australian Department of Transport, Energy and Infrastructure. Retrieved 2008-08-25.
  3. ^ Railway Digest August 2007
  4. ^ "Rail Revitalisation". South Australian Department of Transport, Energy and Infrastructure. Retrieved 2008-08-25.
  5. ^ http://gallery.qrig.org/v/users/Alantrains/Roma+St/DCP_0005.JPG.html Roma Street gauge splitter
  6. ^ 3-Rail, 4-Rail and transition
  7. ^ "Broad gauge to Austria". Railway Gazette. Retrieved 2008-05-15.