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In railroad structures and rail terminology, a wye (like the 'Y' glyph) or triangular junction (often shortened to just triangle) is a triangular joining arrangement of three rail lines with a railroad switch (set of points) at each corner connecting to the incoming lines. A turning wye is a specific case.
Where two rail lines join, or where a Branch line diverges from a railroad's mainline, wyes can be used at a mainline rail junction to allow incoming trains to travel in either direction.
Wyes can also be used for turning railway equipment, and generally cover less area than a balloon loop doing the same job, but at the cost of two additional sets of points to construct and then maintain. These turnings are accomplished by performing the railway equivalent of a three-point turn through successive junctions of the wye. The direction of travel and the relative orientation of a locomotive or railway vehicle thus can be reversed. Where a wye is built specifically for equipment reversing purposes, one or more of the tracks making up the junction will typically be a stub siding.
Tram 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.
Where one or more of the lines forming 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 triangle may incorporate on some of the legs.
Several different techniques can be used to achieve such turning. Turntables require the least space, but can generally only deal with a single piece of equipment at a time. Balloon loop can turn trains of any length — up to the total length of the loop — in a single operation, but require far more space than wyes. Rail wyes can be constructed on sites where a loop would not be possible, and can turn trains up to 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 ) are more likely to be directional than those found on other continents. In Canada and the United States, the railroad often was built before other structures, and railway builders had much more freedom to lay down tracks where they wished. Similarly, when not constrained by space limitations many early Australian railways made use of wyes (particularly in rural locations) for their lower installation and maintenance costs; however, their necessity and use diminished from the 1960s onwards with the major trend in most states toward bidirectional locomotives and railcars.
In Europe, although some use was made of bi-directional 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. Over time, most diesel and electric locomotives ordered in Europe have been designed to be fully bi-directional and normally with two driving cabs. Thus most rail wyes, where they existed, and turntables have been taken out of use.
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 may be able to use side streets or street squares. However, although turning loops are the most common way of turning such vehicles, wye tracks are also sometimes used.
In contrast, the engineering of a terminus station such as Woodville Railway Station, New Zealand avoided this problem by building a balloon loop (reversing loop) so that trains can serve the main station in either direction without the need to reverse. In a midline station where it is desired to reverse a consist or locomotive, a double-track and turning wye arrangement is far more common.
An earlier example may be on the Cromford and High Peak Railway, which had been opened in 1831 as a horse-drawn railway. This appears to have been used for reversing trains of wagons with end doors that have just come up the cable railway to the highest level of the railway before they proceeded down the remaining inclines.Kay, Peter (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. (National Grid location .).Marshall, John (1982). The Cromford & High Peak Railway. Newton Abbot, Devon; and North Pomfret, Vermont: David & Charles. . p. 36.
A number of triangular junctions were built on the Victorian Railways network, both at major junctions, and for turning locomotives and train consists in places where the provision of a turntable was impractical or unnecessarily expensive. These included:
A triangular junction is used to turn tramcars on the Portland Cable Tram line in Portland, Victoria.
The only other operational triangular junction in Ireland is Downpatrick Loop on the Downpatrick and County Down Railway. Originally constructed to allow direct Belfast–Newcastle trains to bypass Downpatrick station, the triangle forms the basis of a heritage railway, the only heritage railway of this type in the British Isles. There is one station at each end of the triangle and another in the southernmost corner.
Historical triangular junctions in Ireland include Moyasta Junction on the West Clare line, the Monkstown/Greenisland/Bleach Green triangle on the Northern Counties Committee and Bundoran Junction on the Great Northern Railway. Though two sides of the former are still in mainline use, the "back line" between Monkstown and Greenisland has been removed, whilst the latter was closed altogether in 1957. Additionally, the Great Northern's largest locomotive yard at Adelaide never had a turntable, using a dedicated turning triangle instead.
The Luas tram system has a triangular junction on the Red Line between the stations of Busáras, Connolly and George's Dock. The line that goes between George's Dock and Connolly is never used, as no trams operate between The Point and Connolly.
Some of these still survive, such as at of Carbonia in Sardinia Via della Stazione, Carbonia CI (OpenStreetMap) and at Mals or Malles Venosta in Val Venosta in the South Tyrol. Mals station (OpenStreetMap)
In addition to small terminal stations such as Carbonia and Malles Venosta, inversion stars were also installed at some principal stations such as Verona Porta Nuova and Brenner at the summit of the Brenner Pass. Locomotives being turned at Verona (14m 30s) and Brenner (16m 00s) (Istituto Luce)
An unusual arrangement, unique in Britain, was constructed at Grantham. Its location was 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 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 constructing an "inside-out" triangle whereby the approach tracks intersected in a scissors crossing.
A typical use for a stub-end passenger station would be as follows: A wye was incorporated at the "throat" where the rows of tracks converged from the station to facilitate the turning of trains. An arriving train came to a stop on the main line after passing the wye. Once the switches on the wye are aligned, the train reversed, with the brakeman at the rear of the last car regulating the speed with the brake lever upon approach to the platform. After coming to a complete stop at the end of the track, passengers were allowed to disembark safely.
Meanwhile, the locomotives could be uncoupled from the train and sent to the engine terminal to be serviced for their next assignment. Then, the head-end cars could be uncoupled from the rest of the train and spotted by a station switcher at the parcel facility where mail and express packages were handled. The departing train was reassembled, freshly cleaned and serviced for the next journey. A steam pipe from the station's steam generator could have been attached to the train's steam line from the rear to supply heat until the locomotives were coupled up front to supply steam.
The train was announced for boarding with a list of destinations. With switches aligned, the train slowly departed to the main line, continuing on its journey or returning toward the direction from which it arrived by rounding the opposite leg from the one it reversed on upon arrival.
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 Trestle bridge and one side is in 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.
A primary feature of the Bay Area Rapid Transit system is the Oakland Wye. Located beneath Downtown Oakland, California, the vast majority of the system's trains run through the wye primarily to and from San Francisco with some services running north and south along the East Bay. This section of track is considered a bottleneck for system-wide capacity based on speed restrictions and timing difficulties from distant branch lines.
The southern terminus of the Auto Train in Sanford, Florida, uses a wye to turn the locomotives around for the return trip north. A road that crosses the eastern side of the wye allows access to the inner part of the wye where there is a rock supply company.
In Arizona, the Grand Canyon Railway (GCRY) has a wye at both the Williams and South Rim/Grand Canyon Village termini of its line. The train is turned around at the South Rim/Grand Canyon Village wye with the passengers on board. At the Williams end, the train is turned around after the passengers disembark.
The Chowchilla Wye is a primary feature of the planned California High-Speed Rail System. It will allow for transfers from feeder services on the third leg and facilitate more routing options as future phases are completed.
Hammel's Wye is a primary feature of the IND Rockaway Line, serving A and Rockaway Park Shuttle trains all day. The wye was named after a past station, Hammels station.
It takes four changes of direction of movement to turn a piece of rolling stock on a reversing star.
There was a "star" layout at the summit of the Brenner Pass, on the Austrian–Italian border. It was still there in 1991, covered over with gravel so that market-stalls could function on top.
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