95-611: The Keddie Wye is a railroad junction in the form of a wye on the Union Pacific Railroad in Plumas County, California , United States. Located at the town of Keddie , it joins the east-west Feather River Route and the "Inside Gateway"—formally, the BNSF Gateway Subdivision —which runs north to Bieber . A notable feat of railroad engineering, it is the world's only wye with two legs on bridges that meet in
190-444: 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
285-553: 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 spur 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
380-424: 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. A triangle may have a situational disadvantage in train operations when space constraints of the local geography cause one leg of triangle to bypass
475-564: A broken red lens could be taken by a driver as a false 'clear' indication. It was not until scientists at Corning Glassworks perfected a shade of yellow without any tinges of green or red that yellow became the accepted colour for 'caution'. Mechanical signals are usually remotely operated by wire from a lever in a signal box, but electrical or hydraulic operation is normally used for signals that are located too distant for manual operation. On most modern railways, colour light signals have largely replaced mechanical ones. Colour light signals have
570-419: A busy commuter line might have blocks a few hundred metres long. A train is not permitted to enter a block until a signal indicates that the train may proceed, a dispatcher or signalman instructs the driver accordingly, or the driver takes possession of the appropriate token. In most cases, a train cannot enter the block until not only the block itself is clear of trains, but there is also an empty section beyond
665-423: A centralized train dispatcher's office that controls railroad interlockings and traffic flows in portions of the rail system designated as CTC territory. Train detection refers to the presence or absence of trains on a defined section of line. The most common way to determine whether a section of line is occupied is by use of a track circuit . The rails at either end of each section are electrically isolated from
760-459: A danger signal for a specific time, although this is only permitted when the signal does not protect any conflicting moves, and also when the signalman is unable to contact the next signal box to make sure the previous train has passed, for example if the telegraph wires are down. In these cases, trains must proceed at very low speed (typically 32 km/h (20 mph) or less) so that they are able to stop short of any obstruction. In most cases, this
855-420: 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 separate single track freight line. The three passenger stations at the vertices of the triangle have island platforms making it convenient to change trains. The sharp curves of the triangle, and especially
950-411: A driver is informed which route the train will take beyond each signal (unless only one route is possible). This is achieved by a route indicator attached to the signal. The driver uses their route knowledge, reinforced by speed restriction signs fixed at the lineside, to drive the train at the correct speed for the route to be taken. This method has the disadvantage that the driver may be unfamiliar with
1045-399: A driver of an upcoming change of route. Under speed signalling , the signal aspect informs the driver at what speed they may proceed over a junction, but not necessarily the route the train will take. Speed signalling requires a far greater range of signal aspects than route signalling, but less dependence is placed on drivers' route knowledge, although the need for drivers to learn the route
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#17328523039491140-449: A green light with a safe condition, this was not historically the case. In the very early days of railway signalling, the first coloured lights (associated with the turned signals above) presented a white light for 'clear' and a red light for 'danger'. Green was originally used to indicate 'caution' but fell out of use when the time interval system was discontinued. A green light subsequently replaced white for 'clear', to address concerns that
1235-515: 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 observation cars ) are more likely to be directional than those found on other continents. In Canada and the United States, the railroad often
1330-425: A main station. In tight city environments, this can happen easily, as it did, for example, at Cootamundra West , Australia and Tecuci , Romania, where extra passenger stations had to be built to serve trains taking the shortcut. 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
1425-519: A number of accidents, most notably the Armagh rail disaster . This required block signalling for all passenger railways, together with interlocking , both of which form the basis of modern signalling practice today. Similar legislation was passed by the United States around the same time. Not all blocks are controlled using fixed signals. On some single track railways in the UK, particularly those with low usage, it
1520-455: A passing place. Neither train is permitted to move before the other has arrived. In the US, the display of two green flags (green lights at night) is an indication that another train is following the first and the waiting train must wait for the next train to pass. In addition, the train carrying the flags gives eight blasts on the whistle as it approaches. The waiting train must return eight blasts before
1615-700: A pentagram layout, requiring four movements and five turnouts to reverse. It allows a smaller layout, without excessively tight curve radii, compared to a triangle. Some of these still survive, such as at the original terminus [ it ] of Carbonia in Sardinia and at Mals or Malles Venosta in Val Venosta in the South Tyrol . 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
1710-421: 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
1805-564: A reversing star is more expensive to build and service. 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. Railway signalling Railway signalling ( BE ), or railroad signaling ( AE ),
1900-558: A safe manner taking this information into account. Generally, the signal remains at danger, and the driver is given verbal authority, usually by a yellow flag, to pass a signal at danger, and the presence of the train in front is explained. Where trains regularly enter occupied blocks, such as stations where coupling takes place, a subsidiary signal, sometimes known as a "calling on" signal, is provided for these movements, otherwise they are accomplished through train orders. The invention of train detection systems such as track circuits allowed
1995-463: A signal box. When a train passed into a block, a signalman would protect that block by setting its signal to 'danger'. When an 'all clear' message was received, the signalman would move the signal into the 'clear' position. The absolute block system came into use gradually during the 1850s and 1860s and became mandatory in the United Kingdom after Parliament passed legislation in 1889 following
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#17328523039492090-453: A speed that they can stop safely should an obstacle come into view. This allows improved efficiency in some situations and is mostly used in the USA. In most countries it is restricted to freight trains only, and it may be restricted depending on the level of visibility. Permissive block working may also be used in an emergency, either when a driver is unable to contact a signalman after being held at
2185-439: A station or signal box to send a message (usually a specific number of rings on a bell ) to confirm that a train had passed and that a specific block was clear. This was called the " absolute block system ". Fixed mechanical signals began to replace hand signals from the 1830s. These were originally worked locally, but it later became normal practice to operate all the signals on a particular block with levers grouped together in
2280-409: A track circuited one. The low ballast resistance of very long track circuits reduces their sensitivity. Track circuits can automatically detect some types of track defect such as a broken rail. In the event of power restoration after a power failure, an axle counted section is left in an undetermined state until a train has passed through the affected section. A track circuited section immediately detects
2375-569: A train to wait in a siding for a priority train to pass, and to maintain at least one block spacing between trains going the same direction. Timetable and train order operation was commonly used on American railroads until the 1960s, including some quite large operations such as the Wabash Railroad and the Nickel Plate Road . Train order traffic control was used in Canada until the late 1980s on
2470-530: A tunnel. The west and north legs of the wye are on bridges over Spanish Creek, and the southeast leg runs through a tunnel (Tunnel No. 32). Just to the northwest, where the two bridged legs join, is Tunnel No. 31. The wye and the town are named for Arthur W. Keddie , who purchased the survey rights and the right to build a railroad through the Feather River Canyon from George Jay Gould , the son of Jay Gould . The Western Pacific Railroad (now part of
2565-504: 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. Railways in Italy used a number of "inversion stars" for turning locomotives. This uses
2660-403: A vast scale, with no requirements for any kind of communication that travels faster than a train. Timetable operation was the normal mode of operation in North America in the early days of the railroad. With the advent of the telegraph in 1841, a more sophisticated system became possible because this provided a means whereby messages could be transmitted ahead of the trains. The telegraph allows
2755-455: A wye (as a refuge siding in lieu of a passing loop ) for a meet with an oncoming train, or to allow a faster one to overtake, and then reverse out to continue in the original direction. 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 flying junctions on some of
2850-598: 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
2945-571: Is grid reference ST316887 . Shrewsbury also has a triangular route formation that was used to turn steam locomotives, and is still available. A triangle, grid reference SH294789 , was provided in 1989 adjacent to the transfer sidings for Wylfa Nuclear Power Station , near to Valley on Anglesey in Wales. This enables the North Wales Coast Line to be used by steam hauled excursions. The turntable at Holyhead has long been removed and
Keddie Wye - Misplaced Pages Continue
3040-497: Is a system used to control the movement of railway traffic. Trains move on fixed rails , making them uniquely susceptible to collision . This susceptibility is exacerbated by the enormous weight and inertia of a train, which makes it difficult to quickly stop when encountering an obstacle. In the UK , the Regulation of Railways Act 1889 introduced a series of requirements on matters such as
3135-414: Is common to use token systems that rely on the train driver's physical possession of a unique token as authority to occupy the line, normally in addition to fixed signals. Before allowing a train to enter a block, a signalman must be certain that it is not already occupied. When a train leaves a block, they must inform the signalman controlling entry to the block. Even if the signalman receives advice that
3230-640: Is known as the method of working (UK), method of operation (US) or safe-working (Aus.). Not all these methods require the use of physical signals , and some systems are specific to single-track railways. The earliest rail cars were hauled by horses or mules. A mounted flagman on a horse preceded some early trains. Hand and arm signals were used to direct the "train drivers". Foggy and poor-visibility conditions later gave rise to flags and lanterns. Wayside signalling dates back as far as 1832, and used elevated flags or balls that could be seen from afar. The simplest form of operation, at least in terms of equipment,
3325-403: Is not allowed during times of poor visibility (e.g., fog or falling snow). Even with an absolute block system, multiple trains may enter a block with authorization. This may be necessary in order to split or join trains together, or to rescue failed trains. In giving authorization, the signalman also ensures that the driver knows precisely what to expect ahead. The driver must operate the train in
3420-463: Is only used for out of service trains. Commuter trains enter the junction from one direction (e.g., the Portadown line ), stop at Grand Central, and then continue out on the other direction towards Bangor station . Commuter trains on NI Railways are all diesel multiple unit railcars, so they do not need to use the junction as a turning method. The only other operational triangular junction in Ireland
3515-426: Is the origin of UK signalmen being referred to as "bob", "bobby" or "officer", when train-crew are speaking to them via a signal telephone) were employed to stand at intervals ("blocks") along the line with a stopwatch and use hand signals to inform train drivers that a train had passed more or less than a certain number of minutes previously. This was called "time interval working". If a train had passed very recently,
3610-419: Is the system's inflexibility. Trains cannot be added, delayed, or rescheduled without advance notice. A third problem is a corollary of the second: the system is inefficient. To provide flexibility, the timetable must give trains a broad allocation of time to allow for delays, so the line is not in the possession of each train for longer than is otherwise necessary. Nonetheless, this system permits operation on
3705-407: Is to run the system according to a timetable. Every train crew understands and adheres to a fixed schedule. Trains may only run on each track section at a scheduled time, during which they have 'possession' and no other train may use the same section. When trains run in opposite directions on a single-track railway, meeting points ("meets") are scheduled, at which each train must wait for the other at
3800-424: Is very difficult to completely prevent conflicting orders being given, it is relatively simple to prevent conflicting tokens being handed out. Trains cannot collide with each other if they are not permitted to occupy the same section of track at the same time, so railway lines are divided into sections known as blocks . In normal circumstances, only one train is permitted in each block at a time. This principle forms
3895-567: The Algoma Central Railway and some spurs of the Canadian Pacific Railway. Timetable and train order was not used widely outside North America, and has been phased out in favour of radio dispatch on many light-traffic lines and electronic signals on high-traffic lines. More details of North American operating methods is given below. A similar method, known as 'Telegraph and Crossing Order' was used on some busy single lines in
Keddie Wye - Misplaced Pages Continue
3990-637: The Amtrak 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
4085-616: 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
4180-509: The IND Rockaway Line , serving A and Rockaway Park Shuttle trains all day. The wye was named after a past station, Hammels station . Convoluted wye , turning star or reversing star ( Italian : Stella di inversione ) is a special wye layout used in places where the space is tight. It has a pentagram -like form and consists of five turnouts (versus three for a wye) and three, four or five diamond crossings . Because of this,
4275-493: The London Underground 's Circle Line ). 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 or turning loops 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
4370-533: The rope-hauled inclines to the highest level of the railway before they proceeded down the remaining inclines. The site of this can still be seen near Hindlow, in Derbyshire . ( National Grid location grid reference ST316887 .). Sefton railway station in Sydney lies on one corner of a triangular junction, which allows trains to branch off in either direction without the need to terminate or change ends. One train
4465-588: The Limerick Junction station, and is also occasionally used to turn steam locomotives on railtours, whilst the latter is used primarily by freight trains running between the Port of Waterford and County Mayo to avoid having to run around in Kilkenny station. In Belfast , Northern Ireland, a triangular junction exists at Grand Central station . It is rarely used to turn locomotives, save the occasional steam engine. It
4560-542: 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
4655-511: The UK during the 19th century. However, a series of head-on collisions resulted from authority to proceed being wrongly given or misunderstood by the train crew - the worst of which was the collision between Norwich and Brundall, Norfolk, in 1874. As a result, the system was phased out in favour of token systems. This eliminated the danger of ambiguous or conflicting instructions being given because token systems rely on objects to give authority, rather than verbal or written instructions; whereas it
4750-760: The Union Pacific) built the tracks along the Feather River in 1909 to complete a route from the San Francisco Bay Area to Salt Lake City, Utah , providing an alternate to the Southern Pacific 's route over Donner Pass . Keddie was the site of the "last spike" ceremony held on November 1, 1909. The Feather River route was preferred by some over the Donner Pass route through the Sierra Nevada because
4845-720: 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
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#17328523039494940-523: The advantage of displaying the same aspects by night as by day, and require less maintenance than mechanical signals. Although signals vary widely between countries, and even between railways within a given country, a typical system of aspects would be: On some railways, colour light signals display the same set of aspects as shown by the lights on mechanical signals during darkness. Route signalling and speed signalling are two different ways of notifying trains about junctions. Under route signalling ,
5035-453: The appropriate position before the signal protecting that route can be cleared. UK trains and staff working in track circuit block areas carry track circuit operating clips (TCOC) so that, in the event of something fouling an adjacent running-line, the track circuit can be short-circuited. This places the signal protecting that line to 'danger' to stop an approaching train before the signaller can be alerted. An alternate method of determining
5130-463: The area re-developed; the sidings at Valley some 4 miles (6.4 km) from the terminus are the nearest suitable site. 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
5225-443: The basis of most railway safety systems. Blocks can either be fixed (block limits are fixed along the line) or moving blocks (ends of blocks defined relative to moving trains). On double tracked railway lines, which enabled trains to travel in one direction on each track, it was necessary to space trains far enough apart to ensure that they could not collide. In the very early days of railways, men (originally called 'policemen', which
5320-436: The block is clear. Most blocks are "fixed", i.e. they include the section of track between two fixed points. On timetable, train order, and token -based systems, blocks usually start and end at selected stations. On signalling-based systems, blocks start and end at signals. The lengths of blocks are designed to allow trains to operate as frequently as necessary. A lightly used line might have blocks many kilometres long, but
5415-500: 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. Many North American passenger terminals in large cities had wye tracks to allow
5510-413: The dissemination of any timetable changes, known as train orders . These allow the cancellation, rescheduling and addition of train services. North American practice meant that train crews generally received their orders at the next station at which they stopped, or were sometimes handed up to a locomotive 'on the run' via a long staff. Train orders allowed dispatchers to set up meets at sidings, force
5605-440: The driver, or rotated so as to be practically invisible. While this type of signal is still in use in some countries (e.g., France and Germany), by far the most common form of mechanical signal worldwide is the semaphore signal . This comprises a pivoted arm or blade that can be inclined at different angles. A horizontal arm is the most restrictive indication (for 'danger', 'caution', 'stop and proceed' or 'stop and stay' depending on
5700-545: The end of the block for at least the distance required to stop the train. In signalling-based systems with closely spaced signals, this overlap could be as far as the signal following the one at the end of the section, effectively enforcing a space between trains of two blocks. When calculating the size of the blocks, and therefore the spacing between the signals, the following have to be taken into account: Historically, some lines operated so that certain large or high speed trains were signalled under different rules and only given
5795-404: The entire train has left the section. If part of the train remains in the section, the track circuit detects that part. This type of circuit detects the absence of trains, both for setting the signal indication and for providing various interlocking functions—for example, preventing points from being moved while a train is approaching them. Electrical circuits also prove that points are locked in
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#17328523039495890-564: The flag carrying train may proceed. The timetable system has several disadvantages. First, there is no positive confirmation that the track ahead is clear, only that it is scheduled to be clear. The system does not allow for engine failures and other such problems, but the timetable is set up so that there should be sufficient time between trains for the crew of a failed or delayed train to walk far enough to set warning flags, flares, and detonators or torpedoes (UK and US terminology, respectively) to alert any other train crew. A second problem
5985-444: The following train was expected to slow down to allow more space to develop. The watchmen had no way of knowing whether a train had cleared the line ahead, so if a preceding train stopped for any reason, the crew of a following train would have no way of knowing unless it was clearly visible. As a result, accidents were common in the early days of railways. With the invention of the electrical telegraph , it became possible for staff at
6080-463: The high point of the former (the Chilcoot Tunnel under Beckwourth Pass ) is at a lower elevation — about 5,000 ft (1,500 m) as opposed to 7,000 ft (2,100 m) — and most of the route is at a gentler grade than the line over Donner Pass. Construction started on the branch running north to Bieber in 1930 and was completed in 1931, along with the north and southeast legs of
6175-411: The implementation of interlocked block signalling and other safety measures as a direct result of the Armagh rail disaster in that year. Most forms of train control involve movement authority being passed from those responsible for each section of a rail network (e.g. a signalman or stationmaster ) to the train crew. The set of rules and the physical equipment used to accomplish this determine what
6270-584: The land is cheap, and also because it provides the most convenient and flexible sectioning arrangements. 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
6365-456: The legs. 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, most steam locomotives and some diesel locomotives , or where the consist has a dedicated tail end car such as an observation car . Even where equipment is symmetrical, periodic turning may still be necessary in order to equalize wear (e.g., on
6460-402: 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
6555-550: 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. The land within a triangle is cut off from the adjacent area (and normally fenced off) and has marginal commercial value, so will be purposed mainly for the railway's exclusive use – generally being used for maintenance depots, storage, or vehicle parking. On electrified lines substations tend to be located inside triangles, in part because
6650-403: The next section, and an electric current is fed to both running rails at one end. A relay at the other end is connected to both rails. When the section is unoccupied, the relay coil completes an electrical circuit, and is energized. However, when a train enters the section, it short-circuits the current in the rails, and the relay is de-energized. This method does not explicitly need to check that
6745-434: The occupied status of a block uses devices located at its beginning and end that count the number of axles that enter and leave the block section. If the number of axles leaving the block section equals those that entered it, the block is assumed to be clear. Axle counters provide similar functions to track circuits, but also exhibit a few other characteristics. In a damp environment an axle counted section can be far longer than
6840-708: 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 trestles 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
6935-452: The power unit at the lower end and seating angled to compensate for the gradient. They therefore have to be turned at the summit should it be necessary to make a through journey. Whilst limitations of space dictated that the triangle had to be partly constructed in tunnels it also ensures that in winter it is snow-free and thus readily available in emergencies. In Britain triangular layouts that could be used for turning locomotives were usually
7030-416: The presence of a train in section. On most railways, physical signals are erected at the lineside to indicate to drivers whether the line ahead is occupied and to ensure that sufficient space exists between trains to allow them to stop. Older forms of signal displayed their different aspects by their physical position. The earliest types comprised a board that was either turned face-on and fully visible to
7125-410: The previous train has left a block, they are usually required to seek permission from the next signal box to admit the next train. When a train arrives at the end of a block section, before the signalman sends the message that the train has arrived, they must be able to see the end-of-train marker on the back of the last vehicle. This ensures that no part of the train has become detached and remains within
7220-575: 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 . In the Republic of Ireland two triangular junctions are in use. One is at Limerick Junction , and the other at Lavistown , near Kilkenny . The former allows direct Limerick–Dublin passenger trains to bypass
7315-408: The replacement of manual block systems such as absolute block with automatic block signalling. Under automatic block signalling, signals indicate whether or not a train may enter a block based on automatic train detection indicating whether a block is clear. The signals may also be controlled by a signalman, so that they only provide a proceed indication if the signalman sets the signal accordingly and
7410-479: The required speed over a junction onto which they have been diverted due to some emergency condition. Several accidents have been caused by this alone. For this reason, in the UK, where all lines are route signalled, drivers are only allowed to drive on routes that they have been trained on and must regularly travel over the lesser used diversionary routes to keep their route knowledge up to date. Many route signalling systems use approach control (see below) to inform
7505-520: 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 National Grid location
7600-636: The right of way if two blocks in front of the train were clear. Under a moving block system, computers calculate a safe zone around each moving train that no other train is allowed to enter. The system depends on knowledge of the precise location and speed and direction of each train, which is determined by a combination of several sensors such as radio frequency identification along the track, ultra-wideband, radar, inertial measurement units, accelerometers and trainborne speedometers ( GNSS systems cannot be relied upon because they do not work in tunnels). Moving block setups require instructions to be directly passed to
7695-424: The section. The end of train marker might be a coloured disc (usually red) by day or a coloured oil or electric lamp (again, usually red). If a train enters the next block before the signalman sees that the disc or lamp is missing, they ask the next signal box to stop the train and investigate. Under a permissive block system, trains are permitted to pass signals indicating the line ahead is occupied, but only at such
7790-520: 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. 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
7885-417: 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,
7980-399: 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
8075-508: The summit of the Brenner Pass . 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 dead-end station at Tsumeb for trains travelling directly between the new extension towards Angola and Windhoek . This direct bypass line can save an hour of shunting time, particularly if
8170-495: 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. The use of triangular junctions allows flexibility in routing trains from any line to either of the two other paths, without the need to reverse the train. For this reason they are common across most rail networks. A slower train may be signaled to temporarily enter
8265-441: The train instead of using lineside signals. This has the advantage of increasing track capacity by allowing trains to run closer together while maintaining the required safety margins. Centralized traffic control (CTC) is a form of railway signalling that originated in North America. CTC consolidates train routing decisions that were previously carried out by local signal operators or the train crews themselves. The system consists of
8360-512: The train is longer than the loops in the station. There is a turning triangle partly tunnelled into the mountain at Kleine Scheidegg at the summit of the 800mm gauge Wengernalpbahn in the Bernese Oberland , Switzerland. Kleine Scheidegg is reached from two lower termini, Lauterbrunnen and Grindelwald , located on opposite sides of the col . Trains normally descend in the direction they have arrived from and are designed accordingly with
8455-620: 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 Station , which has a double wye, the Saint Paul Union Depot , and the Memphis Union Station . 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
8550-567: The turnouts on those sharp curves, restrict train speeds to between 10 and 50 km/h (6.2 and 31.1 mph). Near Hamilton station on the Central Coast and Newcastle line there is a wye for freight trains and regional trains. This puts them directly on the main northern line 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
8645-409: The type of signal). To enable trains to run at night, one or more lights are usually provided at each signal. Typically this comprises a permanently lit oil lamp with movable coloured spectacles in front that alter the colour of the light. The driver therefore had to learn one set of indications for daytime viewing and another for nighttime viewing. Whilst it is normal to associate the presentation of
8740-403: The use of triangular junctions and reversing wyes on streetcar and tram 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
8835-778: The wye. This allowed the Western Pacific to diverge from its east-west route (along the west leg of the wye) and go north to an interchange with the Great Northern Railway (now BNSF Railway ) and its traffic from the Pacific Northwest . The Keddie Wye is a favorite railfan spot and is part of Plumas County's 7 Wonders of the Railroad World . Access to the site is described in the county travel guide. 40°01′06″N 120°57′27″W / 40.01844°N 120.95760°W / 40.01844; -120.95760 Wye (railroad) In railroad structures and rail terminology ,
8930-483: 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
9025-621: 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. 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. Similar considerations as for mainline rail systems apply to
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