A wye or triangular junction, in rail terminology, is a triangular shaped arrangement of rail tracks with a switch or set of points at each corner. In mainline railroads, this can be used at a rail junction, where three rail lines join, in order to allow trains to pass from any line to any other line.
Wyes can also be used 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 in the direction from which it came. Where a wye is built specifically for turning purposes, one or more of the tracks making up the junction will typically be a stub siding.
Tram or streetcar tracks also make use of triangular junctions and sometimes have a short triangle or wye stubs to turn the car at the end of the line.
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The use of triangular junctions allows flexibility in routing trains from any line to any other line, without the need to reverse the train. For this reason they are common across most rail networks. Slower bi-directional trains may enter a wye, letting a faster one pass, and continue on the same direction providing service to nearby freight transport or a passenger station.
Where one or more of the lines meeting at the junction are multi-track, the presence of a triangular junction does introduce a number of potential conflicting moves. For this reason, where traffic is heavy, the junction may incorporate flying junctions on some, or all, or the legs of the triangle.
From time to time it is necessary to turn both individual pieces of railroad equipment or whole trains. This may be because the piece of equipment is not directionally symmetrical, for example in the case of most steam locomotives and, in certain parts of the world, diesel locomotives, or where the train needs to run a particular direction, for example where it has dedicated tail end car such as an observation car. Even where equipment is symmetrical, periodic turning may still be necessary in order to even wear.
There are several different techniques that can be used to achieve such turning. Rail turntables require the least space, but can generally only deal with a single piece of equipment at a time. Balloon or turning loops can turn trains of any length in a single operation, but require far more space than wyes[1]. Rail wyes can be constructed on sites where a loop would not be possible, and can turn trains up the length of the stub tracks at the end of the wye.
Railroad systems in North America and Australia have tended to have more wyes than railroads elsewhere. North American locomotives and cars (such as observation cars) tend to be 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.
In Europe, although some use was made of bi-directional tank locomotives and push-pull trains, most steam locomotives were uni-directional. Because of land usage considerations turntables were normally used to turn such locomotives, and most terminal stations and locomotive depots were so equipped. However most diesel and electric locomotives ordered in Europe have been designed to be fully bi-directional, symmetrical and normally with two driving cabs. Thus most turntables and, where they existed, rail wyes, have been taken out of use.
Similar considerations apply to the use of triangular junctions and reversing wyes on streetcar and tram systems, as apply to mainline rail systems. Many, although by no means all, streetcar and tram systems use single ended vehicles that have doors on one side only and that must be turned at each end of the route.
However the vehicles used on such systems tend to have much smaller minimum curvature requirements than heavy rail equipment. This renders the use of a balloon loop more practical in a small amount of space, and with street-running vehicles such a loop can make of side streets or street squares. However, although turning loops are the most common way of turning such vehicles, wye tracks are also sometimes used.
A triangle has a disadvantage if a train by taking the triangle bypasses a main station. This happened at Cootamundra West where an extra passenger station had to be built to serve trains taking the shortcut.
Woodville Railway Station, New Zealand avoids this problem by building a balloon loop so that trains can serve the main station in either direction without the need to reverse.
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.
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 proceeded down the remaining inclines.[2] The site of this can still be seen near Hindlow, in Derbyshire, SK093685.[3]
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). 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.
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 North Western Transportation Company wye and crossover nearby.
Metro-North Railroad maintains a very busy wye at Mott Haven, New York, in the Bronx. New Haven Line and Harlem Line trains use this wye to access the Hudson Line to reach the Yankees – East 153rd Street station.
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 grid reference ST316887. Shrewsbury also has a triangular route formation that was used to turn steam locomotives, and is still available. Valley railway station on Anglesey in Wales still retains its triangle, grid reference SH294789 which is occasionally used for turning charter trains or diesel hauled Pendolino electric sets terminating 4 miles (6.4 km) away at Holyhead.
An unusual arrangement, unique in Britain, was constructed at Grantham. Its location was grid reference 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.
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. [1] This direct bypass line can save 60 minutes shunting time, particularly if the train is longer than the loops in the station.
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