Wye (rail)

A triangle or wye, in rail terminology, is a triangular shaped arrangement of railway tracks with a switch (point) at each corner. In mainline railroads, this is used at a railway junction, where two railways join, or cross over. It can also be used as a stub for turning railway equipment. By performing the railway equivalent of a three point turn the direction of a locomotive or railway vehicle can be swapped around, leaving it facing the way it came from. Streetcar tracks sometimes have a short triangle or wye stubs to turn the car at the end of the line.

Overview

Turning is required for any directional piece of railroad equipment, such as most steam locomotives, or indeed many passenger trains, especially those that have a dedicated tail end car such as an observation car.

Individual locomotives and railroad cars can be turned on a turntable, but a whole train consist cannot be turned in one operation as it would be longer than the diameter of the turntable. In a wye/triangle configuration any length of train can be turned, as long as it fits entirely beyond the lengths of track leading from each corner.

Railroad systems in North America and Australia have tended to have more wyes than railroads elsewhere in the World. North American locomotives and cars (such as observations carriages) are much more likely to be directional than those found on other continents. In Canada and the United States, the railroad often came first and railway builders had much more freedom to lay down tracks where they wished. Australia has a large amount of open space, and similarly at many rural railway locations in Australia triangles were used as an alternative to turntables for reasons of space availability and cost saving.

Historically, in Europe, extensive use has been made of bi-directional tank locomotives and push-pull trains. Diesel and electric locomotives ordered in Europe have generally been designed to be fully bi-directional, symmetrical and normally with two driving cabs.

A related method for turning long trains at once is to pull them around a loop or "balloon-shaped" section of track.

Oldest

The earliest British (and possibly worldwide) example is the double-tracked triangle within Earlestown railway station on the Liverpool and Manchester Railway, which was completed by the Grand Junction Railway in 1837. The triangle has two passenger platform faces on each of its three sides and five of the six platforms are in frequent (half-hourly etc) use by passenger trains. When steam engines were in regular use the triangle (which is of course also traversed by freight trains) was also used to turn locomotives and can still be so used.

There is an example on the Cromford and High Peak Railway, which was opened in 1831 as a horse-drawn railway, which may be earlier. This appears to have been used for reversing trains of wagons with end doors that have just come up the rope-hauled inclines to the highest level of the railway before they proceded down the remaining inclines [Kay, Peter, (director), 1997, "The Cromford & High Peak Railway: Part 2 - Memories of the High Peak", Stafford, Robert Cartwright Productions, DVD] . The site of this can still be seen near Hindlow, in Derbyshire, gbmappingsmall|SK093685 [Marshall, John, 1982, "The Cromford & High Peak Railway", Newton Abbot, David & Charles, ISBN 0 7153 8128 8, p36] .

Examples

Oceania

Sefton railway station, Sydney, lies on one corner of a triangular junction. The triangle junction allows trains to branch off in either direction, without the need to terminate or change end. One train a day from Birrong to Sefton does terminate and reverse at Regents Park station (in order to clean the rust off the crossover rails)Fact|date=January 2008. There is a goods branch from Chullora, and in the future the possibility of a proposed separate single track freight line. The three passenger stations at the vertices of the triangle have island platforms which make it convenient to change trains. The sharp curves of the triangle and especially the turnouts on those sharp curves restrict train movement speeds to between 10 km/h and 50 km/h.

North America

Many North American passenger terminals in large cities had wye tracks to allow the turning and backing of directional passenger trains onto a main line. Freight traffic could bypass the terminal through the wye. Notable examples include the Los Angeles Union Passenger Terminal, which has a double wye, and the Saint Paul Union Depot.

The Keddie Wye in Keddie, California, was built by the Western Pacific Railroad and is a remarkable engineering feat. Two sides of the wye are built on tall trestles and one side is a tunnel bored through solid rock.

The town of Wyeville, Wisconsin is named after the Union Pacific Railway, formerly the Chicago and Northwestern Railway wye and crossover nearby.

Europe

In Britain triangular layouts that could be used for turning locomotives were usually the result of junctions of two or more lines, there are many examples, including the one known as the Maindee triangle in Newport, South Wales. Here the ex-GWR South Wales mainline from London to Swansea is joined by another GWR line from Shrewsbury via Hereford. The significance of it is that steam-hauled trains can run to Newport and their engines be turned using the triangle. Its OS National Grid location is gbmapping|ST316887. Shrewsbury also has a triangular route formation that was used to turn steam locomotives, and is still available. Holyhead railway station on Anglesey in Wales still retains its triangle, gbmapping|SH294789 which is occasionally used for turning charter trains or diesel hauled Pendolino electric sets.

An unusual arrangement, unique in Britain, was constructed at Grantham. Its location was gbmapping|SK914349 and it is shown on the 1963 edition of OS 1 inch to 1 mile sheet 113. It was built in the 1950s after the turntable at the locomotive shed failed and expenditure on a replacement was no longer justified. Locomotives requiring to be turned had to travel to Barkston Junction to traverse the triangular layout there (this was where "Mallard" with a dynamometer car attached was turned before starting out south on its record-breaking run on 3 July 1938). The journey to Barkston Junction and back was a time consuming business involving a round trip of some 8 miles (13 km) along the busy East Coast Main Line. Eventually authority was given to construct a turning arrangement on a strip of spare land to the west of the main line, just south of Grantham station. There was insufficient space for a conventional triangle but this was overcome by laying a short length of track at right angles to the main line and arranging the approach tracks to intersect in a scissors crossing.

Africa

Tsumeb railway station in Namibia has two triangles. The first and smaller one is for turning engines and is near the station. The second and larger one is to bypass the deadend station at Tsumeb for trains travelling directly between the new extension towards Angola and Windhoek. [http://imageatlas.globexplorer.com/ImageAtlas/view.do?group=ImageAtlas&lat=-19.252&lon=17.712&zoom_level=10] This direct bypass line can save 60 minutes shunting time, particularly if the train were longer than the loops in the station.

Land usage

The land within a triangle tends to be cut off from the adjacent suburbs, and has marginal value, mainly for railway uses, such as maintenance depots. The triangular shape tends to be unsuited for rectangular buildings. On electrified lines, substations tend to be located inside triangles, in part because the land is cheap, and also because it provides the most convenient and flexible sectioning arrangements. Indeed Sefton triangle contains such a substation. Because it is difficult to see approaching trains, the Sefton triangle depot has a level crossing protected by flashing lights.

References

See also

* loop, another method of turning long trains at once.
* Turntable, a rotating platform for turning single carriages or very short trains.