Dual gauge
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Image:Dualgauche.jpg Image:DualgaugeHakonetozanJP14.jpg Dual-gauge or mixed-gauge railway is a special configuration of railway track, allowing trains of different gauges to use the same alignment. 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 one inner allow a narrower gauge. Thus one of the rails is common to all traffic. This configuration is not to be confused with the electric third-rail.
Reasoning
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 sets of tracks (having two rails each) with one set of track, with 3 rails. This allows one rail fewer for the stretch of the dual gauge line, but there are other complications and costs, which 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
Image:CombinedTrack.jpg For dual-gauge to work with 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 1435 mm (4 ft 8½ in, standard gauge) and 1676 mm (5 ft 6 in) can be dual gauged without problem, while 1435 mm (4 ft 8½ in) and 1600 mm (5 ft 3 in, Irish gauge) can also be dual-gauged albeit with lighter narrow footed rails, as shown in Victoria, Australia (where the majority of the railways use the 1600 mm gauge). On the other hand, metre gauge (3 ft 3.4 in) and 1067 mm (3 ft 6 in) as found in Africa are too similar to work in three-rail dual gauge.
If three-rail dual gauge is impossible, then four-rail dual gauge may be possible.
Configuration for Africa
Image:Africa four rail triple gauge.png
1067 mm and 1000 mm gauges found in Africa are too close to allow 3-rail dual gauge. 4-rail dual gauge is required. With a little care, the sleepers for this dual gauge configuration can be made to support triple gauge, including the standard gauge of 1435 mm, at little extra cost.
 1000 mm and 1067 mm gauges are too close to allow 3-rail dual gauge |
 1000 mm and 1067 mm gauges can be commoned with 4 rail dual gauge |
 1000 mm and 1067 mm gauges can be commoned with 4 rail dual gauge with bonus 1435 mm gauge |
An advantage of the four-rail dual gauge track is that the four rails combined to give some of the greater strength of two rails of double the weight. The allows the old rails to be reused to some extent, instead of being scrapped and used for fenceposts.
Example in Africa
2004
On 12 Oct 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 the world standard 1435 mm gauge. Fortunately, all three gauges can be supported by the same sleepers (railroad ties), as described above.
2006
An Indian proposal surfaced to link Benin and Togo on the sea with landlocked Burkino Faso and Niger. The other adjacent state of Ghana and Nigeria use the incompatible 1067mm gauge. With the future in mind, steel and concrete sleepers, at least between stations, can and should cater for three gauges, 1000mm, 1067 and 1435mm.
Gauge conversion
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 wider-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 extra holes are impossible, and the whole sleeper has to be replaced, unless extra boltholes are already allowed for.
During the conversion of the Melbourne to Adelaide line in Australia from 5' 3" to 4' 8½, dual gauge with heavy rails was not possible as the rail footings were too wide. A special gauge convertible sleeper with a chair for the Pandrol clip that was reversible allowed a 2-week conversion process.
In the Adelaide metropolitan area, broad-gauge timber sleepers are being replaced with gauge-convertible concrete sleepers, just in case of future gauge conversion.
During WW1 and WW2, gauge conversion occurred backwards and forwards between Europe and Russia as the fronts and national borders chopped and changed.
The dual-gauge lines in Java were regauged to the narrower gauge (4' 8½" to 3' 6") during the Japanese occupation period 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 were already dual-gauge (some only recently dual-gauged).
Cost of an example
In 2005, Pakistan Railways started work on the conversion of the 128km Mirpurkhas to Khokhra Par (town) line from 1000 mm to 1676 mm gauge. The cost was set at Rs 1,800,000,000 (US$30,000,000), or about Rs 250,000 per km.
Examples
Image:Dual gauge track near Jindrichuv Hradec in Czechia.jpg
In Britain, the Great Western Railway initially ran broad-gauge traffic. Eventually, 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 with dual-gauge tracks; however, its current third and fourth rails are for electricity supply, not a dual gauge.
In Ireland, dual-gauge track was not used in regauging the Ulster Railway (UR). When it regauged from 1879 mm (6 ft 2 in) to the new standard of 1600 mm (5 ft 3 in), the Ulster Railway merely regauged their double-track route in two halves. The Dublin & Drogheda Railway (D&DR) meanwhile were regauging from 1575 mm (5 ft 2 in), too similar to the new gauge to allow dual gauge. Dual gauge was used in Londonderry, by the Port Authority, in an on-street network to transfer goods, on either gauge, between the city's four stations (two 3 ft narrow gauge, two 5 ft 3 in broad gauge).
In Stuttgart, Germany, the public transit authority uses dual gauge rail on several sections, so that both streetcars, which normally operate amongst auto traffic and are thus smaller, and U-Bahn, which are a bit larger, can operate on the same tracks.
In the Czech Republic, one can find dual gauge rail near Jindřichův Hradec where 1435 mm and 760 mm gauges are placed on the same length of track. Interestingly, the two gauges are used by different railway companies.
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 Western Australia, there is a double-track dual-gauge (3' 6" & 4' 8½") main line from East Perth to Northam, about 120 km. Dual gauge track is also used between the triangle at Woodbridge to Cockburn Junction, then to Kwinana on one branch, and North Fremantle on the other.
In Brisbane, Queensland, shorter incidences of dual-gauge track (3' 6" & 4' 8½") exist between the rail freight yards at Acacia Ridge and the Port of Brisbane for freight trains. A dual-gauge line branches from this track 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 latter track is for standard gauge interstate CountryLink XPT services to Sydney.
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 in Japan. For example, part of the Ōu line becomes a 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 first build the 4' 8½" gauge line in 1867. The third track was installed to allow passengers and goods traveling over the 3' 6" gauge Staatsspoorweg (State Railway) a direct connection without requiring transfer on 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 3' 6" 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 3' 6" and 2' 5½" (750 mm) line existed in North Sumatra on a joint line of the Deli Railway and the Aceh Tramway. This line survived in operation to the 1970s.
Some sugar mill railways in Java also have dual-gauge sections.
In Vietnam, dual gauge (meter and standard) occurs between Hanoi and the Chinese border.
Triple gauge
There have been a few instances of triple-gauge break-of-gauge stations.
- Port Pirie, South Australia, 3' 6", 4' 8½", 5' 3" (1938-1970)
- Gladstone, South Australia, 3' 6", 4' 8½", 5' 3" (1970-1980s)
- Peterborough, South Australia, 3' 6", 4' 8½", 5' 3" (1970-1980s)
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.
Accidents on dual-gauge railways
Image:Switch-bifurcation of dual gauge rail near Jindrichuv Hradec.jpg On September 9, 2004, an accident happened on a switch in Jindřichův Hradec 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 in the direction of narrow-gauge track although the express train used the standard-gauge one. Only the driver of the express train was slightly injured.
Complexity of dual-gauge switches
Dual-gauge turnouts (aka switches aka 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), it is sometimes done without any moving parts.
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:
- Albury, New South Wales to Melbourne, Victoria, 300 km
- As the old and original broad gauge track declines in use, it is slated for conversion to standard gauge, replacing parallel standard-gauge single track and broad-gauge double track with a double track standard gauge line. This will reduce delays on the standard-gauge line at crossing loops.
- Melbourne Victoria, to Geelong, Victoria - 80 km - a single standard-gauge line parallel to double-track broad gauge.
- Yogyakarta-Solo in Java, Dutch East Indies during pre-WW II days, 58 km. This had a single 3' 6" line parallelling a dual-gauge 4' 8½" and 3' 6" line.
- In 2005 a proposed standard gauge line connecting Iran with China via several broad gauge Central Asian countries will use a mixture of parallel but separate lines and dual gauge.
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 which links the east and west rail systems is also dual gauge.
Other methods of handling multiple gauges
Other methods of handling multiple gauges include:
- Transporter wagons or transporter trucks, which carry equipment of one gauge on the other's tracks.
- Truck exchange systems, where the railroad car is lifted and the trucks/bogies under it are swapped. This system is not suitable for four-wheel wagons.
- Adjustable gauge equipment (variable gauge axles), in which the wheel gauge can be widened or narrowed.
- Transshipment; transferring goods or people from one set of railroad cars to another.
- Containerisation.
Dual gauge dual voltage
A mini-metro in Gijon, Spain is to be both dual gauge (1000 mm/1676 mm) and dual voltage (1500 V DC/3000 V DC).
See also
- Gantlet track, Gantlet track
- Railroad switch (points)
- History of rail transport by country
- Rail gauge
- Rail terminology
- Rail transport
- Rail transport by country
- Break-of-gauge
- Variable gauge axles