Editing Railroad switch (section)

== Types ==
Apart from the standard right-hand and left-hand switches, switches commonly come in various combinations of configurations.

=== Slip switches ===

==== Double slip ====
[[File:Double slip at Munich central.jpg|thumb|upright|A double switch, or double slip—the points are set to connect the upper left and lower right tracks.]]

A ''double slip switch'' (''double slip'') is a narrow-angled diagonal flat crossing of two lines combined with four pairs of points in such a way as to allow vehicles to change from one straight track to the other, alternatively to going straight across. A train approaching the arrangement may leave by either of the two tracks on the opposite side of the crossing. To reach the third possible exit, the train must change tracks on the slip and then reverse.

The arrangement gives the possibility of setting four routes, but because only one route can be traversed at a time, the four blades at each end of the crossing are often connected to move in unison, so the crossing can be worked by just two levers or point motors. This gives the same functionality of two points placed end to end. These compact (albeit complex) switches usually are found only in locations where space is limited, such as station throats (i.e. approaches) where a few main lines spread out to reach any of numerous platform tracks.

In North American English, the arrangement may also be called a ''double switch'', or more colloquially, a ''puzzle switch''. The [[Great Western Railway]] in the United Kingdom used the term ''double compound points'', and the switch is also known as a ''double compound'' in [[Victoria (Australia)]]<!-- And the rest of Australia?? -->. In Italian, the term for a double switch is {{lang|it|deviatoio inglese}}, which means ''English switch''. Likewise, it is called {{lang|nl|Engels(e) Wissel}} in Dutch and, occasionally, {{lang|de|Engländer}} ("english one", literally "Englishman") in German.

==== Single slip ====
A ''single slip switch'' works on the same principle as a double slip, but provides for only one switching possibility. Trains approaching on one of the two crossing tracks can either continue over the crossing, or switch tracks to the other line. However, trains from the other track can only continue over the crossing, and cannot switch tracks. This is normally used to allow access to sidings and improve safety by avoiding having switch blades facing the usual direction of traffic. To reach the sidings from what would be a facing direction, trains must continue over the crossing, then reverse along the curved route (usually onto the other line of a double track) and can then move forward over the crossing into the siding.

==== Outside slip ====
[[File:2001-07-19.0004.DKW-Baeseler.jpg|thumb|left|upright|A double, outside slip in Heidelberg main station]]

An ''outside slip switch'' is similar to the double or single slip switches described above, except that the switch blades are outside of the diamond instead of inside. An advantage over an inside slip switch is that trains can pass the slips with higher speeds. A disadvantage over an inside slip switch is that they are longer and need more space.

An outside slip switch can be so long that its slips do not overlap at all, as in the example pictured. In such a case a single, outside slip switch is the same as two regular switches and a regular crossing.  Double outside slip switches are only used in rare, specific cases.

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=== Crossover <span class="anchor" id="Scissors crossover"></span> ===
<!--"Scissors crossing" redirects here.-->
[[File:Überleitstelle Richthof.JPG|thumb|left|A double crossover at {{lang|de|Richthof}} between {{lang|de|[[Kirchheim, Hesse|Kirchheim]]}} and {{lang|de|Langenschwarz}} stations on the [[Hanover–Würzburg high-speed railway|{{lang|de|Hanover–Würzburg|nocat=yes}} high-speed railway]]]]
[[File:Scissors crossing Demachiyanagi.JPG|thumb|A scissors crossover: two pairs of switches linking two tracks to each other in both directions]]

A ''crossover'' is a pair of switches that connects two parallel [[rail track]]s, allowing a train on one track to cross over to the other. Like the switches themselves, crossovers can be described as either ''facing'' or ''trailing''.

When two crossovers are present in opposite directions, one after the other, the four-switch configuration is called a ''double crossover''. If the crossovers in different directions overlap to form an ×, it is dubbed a ''scissors crossover'', ''scissors crossing'', or just ''scissors''; or, due to the diamond in the center, a ''diamond crossover''. This makes for a very compact track layout at the expense of using a [[level junction]].

In a setup where each of the two tracks normally carries trains of only one direction, a crossover can be used either to detour "wrong-rail" around an obstruction or to reverse direction. A crossover can also join two tracks of the same direction, possibly a pair of local and express tracks, and allow trains to switch from one to the other.

On a crowded system, routine use of crossovers (or switches in general) will reduce throughput, as use of the switch blocks multiple tracks. For this reason, on some high-capacity [[rapid transit]] systems, crossovers between local and express tracks are not used during normal [[rush hour]] service, and service patterns are planned around use of the usually [[flying junction]]s at each end of the local-express line.

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=== Stub switch ===
[[File:Railroad switch Boucher.jpg|thumb|upright|Closeup of a stub switch in Pennsylvania]]
[[File:Stub switch at Welsh Slate Museum.jpg|thumb|upright=1.1|left|A narrow-gauge ''stub switch''—this switch has an additional piece of movable rail instead of a frog.]]

A ''stub switch'' lacks the tapered points (point blades) of a typical switch. Instead, both the movable rails and the ends of the rails of the diverging routes have their ends cut off square. The switch mechanism aligns the movable rails with the rails of one of the diverging routes. In 19th century US railroad use, the stub switch was typically used in conjunction with a [[harp switch stand]].

The rails leading up to a stub switch are not secured to the sleepers for several feet, and rail alignment across the gap is not positively enforced. Stub switches also require some [[flexibility]] in the rails (meaning lighter rails), or an extra joint at which they hinge. Therefore, these switches cannot be traversed at high speed or by heavy traffic and so are not suitable for main line use. A further disadvantage is that a stub switch being approached from the diverging route that is not connected by the points would result in a derailment. Yet another disadvantage is that in very hot weather, expansion of the steel in the rails can cause the movable rails to stick to the stock rails, making switching impossible until the rails have cooled and contracted.

One advantage to stub switches is that they work better in the snow. The sideways action of the point rails pushes snow to the side, instead of packing the snow between the points and the rail in a more modern design.

Stub switches were more common in the very early days of railways and their tramway predecessors. Now, because of their disadvantages, stub switches are used primarily on [[Narrow-gauge railway|narrow-gauge]] and branch lines.

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=== Three-way switch ===
[[File:ThreeWayStub.jpg|thumb|A three-way stub switch at Sheepscot station on the [[Wiscasset, Waterville and Farmington Railway]]]]

A ''three-way switch'' is used to split a railroad track into three divergent paths rather than the more usual two. There are two types of three-way switches. In a ''symmetrical three-way switch'', the left and right branches diverge at the same place. In an ''asymmetrical three-way switch'', the branches diverge in a staggered way using two [[#Interlaced turnout|interlaced turnouts]]. Both types of three-way switches require three frogs.

The complexity of symmetrical switches usually results in speed restrictions, therefore three-way switches are most often used in stations or depots where space is restricted and low speeds are normal. Symmetrical switches were used quite often on Swiss narrow-gauge railways. Asymmetrical three-way switches are more common, because they do not have speed restrictions compared to standard switches. However, because of their higher maintenance cost due to special parts as well as asymmetric wear, both types of three-way switches are replaced with two standard switches wherever possible.

In areas with very low speeds, like depots, and on railroads that had to be built very cheaply, like logging railroads, three-way switches were sometimes built as stub switches.

=== Plate switch ===
[[File:Plate switch at Welsh Slate Museum.jpg|thumb|left|upright=0.5|A narrow-gauge ''plate switch'']]

A ''plate switch'' incorporates the tapered points of a typical switch into a self-contained plate. Each point blade is moved separately by hand. Plate switches are only used for double-flanged wheels, with wheels running through the plates on their flanges, guided by the edges of the plate and the movable blade.

=== Off-railer ===
The off-railer is a system of installing a turnout over and above some plain track, without having to cut or replace that track. It is useful for installing temporary branches on agricultural railways, and sidings for track machines on mainline rails. Special ramps lift the wheels off the normal track, and then the off-railer curves away as required. [[Decauville]] has such a system.
<ref>{{cite magazine |url=https://shop.lrrsa.org.au/product/light-railways-230-april-2013-pdf-download/ |title=Portable Railway Track for Light Railways |last=Zelmer |first=Lynn |date=April 2013 |magazine=[[Light Railways]] |location=Surrey Hills, Melbourne |publisher=[[Light Railway Research Society of Australia]] |issn=0727-8101 |pages=12–19 |access-date=13 April 2025 }}</ref> 
It is similar to a [[Level junction#Drawbridge crossing|drawbridge]] crossing.

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=== Interlaced turnout ===
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An ''interlaced turnout'' is a method of splitting a track into three or more divergent paths. It is an arrangement of two standard turnouts, usually one left- and one right-handed, in an "interlaced" fashion. The points of the second turnout are positioned between the points and the frog of the first turnout. In common with other forms of three way turnouts an additional frog is required. Due to the inherent complexity of the arrangement, interlaced turnouts are normally only used in locations where space is exceptionally tight, such as station throats or industrial areas within large cities.{{Citation needed|date=April 2025}}

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=== Wye switch ===
[[File:Points near Ravenstein.jpg|thumb|A ''wye switch'' on the mainline, leading to a single-track bridge, near [[Ravenstein, Netherlands]]]]

A ''wye switch'' (''Y points'') has trailing ends which diverge symmetrically and in opposite directions. The name originates from the similarity of their shape to that of the letter Y. Wye switches are usually used where space is at a premium. In North America this is also called an "equilateral switch" or "equilateral turnout". Common switches are more often associated with mainline speeds, whereas wye switches are generally low-speed yard switches.

One advantage of wye switches is that they can have a coarser frog angle using the same radius of curvature than a common switch. This means that they give rise to a less severe speed restriction than the diverging branch of a common switch, without having to resort to more expensive switches with a moving frog. For this reason they are sometimes used on a main line where it splits into two equally important branches or at the ends of a single track section in an otherwise double track line.

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=== Run-off points ===
{{Main|Catch points}}
[[File:StokeGiffordYard-catchpoints.jpg|thumb|left|Trap points at the exit from a [[Classification yard|yard]]]]

''Run-off points'' are used to protect main lines from stray or runaway cars, or from trains passing signals set at danger. In these cases, vehicles would otherwise roll onto and foul (obstruct) the main line and cause a collision. Depending on the situation in which they are used, run-off points are referred to either as trap points or catch points. Derailers are another device used for the same purpose.

''Catch points'' are installed on the running line itself, where the railway climbs at a steep gradient. They are used to prevent runaway vehicles colliding with another train further down the slope. In some cases, catch points lead into a sand drag to safely stop the runaway vehicle, which may be traveling at speed. Catch points are usually held in the 'derail' position by a spring. They can be set to allow a train to pass safely in the downhill direction using a lever or other mechanism to override the spring for a short time.

Catch points originate from the days of the 'unfitted' goods (freight) train. As these trains tended to consist of either completely unbraked wagons (relying entirely on the locomotive's own brakes), or ones with unlinked, manually applied brakes (necessitating a stop at the top of steep downgrades for the guard to walk along the train and set the brakes on each wagon in turn), they also lacked any mechanism to automatically brake runaway cars. Catch points were therefore required to stop the rear portion of a poorly coupled train that might break away while ''climbing'' a steep grade – although they would also stop vehicles that ran away for any other reason. Now that trains are all 'fitted' (and broken couplings are far less common), catch points are mostly obsolete.

Similar to catch points, ''trap points'' are provided at the exit from a siding or where a goods line joins a line that may be used by passenger trains. Unless they have been specifically set to allow traffic to pass onto the main line, the trap points will direct any approaching vehicle away from the main line. This may simply result in the vehicle being derailed, but in some cases a sand drag is used, especially where the vehicle is likely to be a runaway traveling at speed due to a slope.

==== Derailers ====
{{Main|Derail}}

A ''derailer'' works by derailing any vehicle passing over it. There are different types of derailers, but in some cases they consist of a single switch point installed in a track. The point can be pulled into a position to derail any equipment that is not supposed to pass through.

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=== Dual gauge switches ===
[[File:DualgaugeHakonetozanJP14.jpg|thumb|A dual-gauge switch in Japan]]

''Dual gauge switches'' are used in [[dual gauge]] systems. There are various possible scenarios involving the routes that trains on each gauge may take, including the two gauges separating or one gauge being able to choose between diverging paths and the other not. Because of the extra track involved, dual gauge switches have more points and frogs than their single gauge counterparts. This limits speeds even more than usual.

A related formation is the 'swish' or rail exchange, where (usually) the common rail changes sides. These have no moving parts, the narrower gauge wheels being guided by [[Guard rails (railroad)|guard rails]] as they transition from one rail to another. The wider gauge only encounters continuous rail so is unaffected by the exchange. At dual gauge turntables, a similar arrangement is used to move the narrow-gauge track from one side to a central position.

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=== Rack-railway switches ===
[[File:Rack railway turnout (SPB).JPG|thumb|left|[[Rack railway#Riggenbach (1871)|Railroad switch]] of the [[Schynige Platte Railway]] (at [[Schynige Platte]], Switzerland)]]

[[Rack railway|Rack-railway]] switches are as varied as rack-railway technologies. Where use of the rack is optional, as on the [[Zentralbahn]] in Switzerland or the [[West Coast Wilderness Railway]] in [[Tasmania]], it is common to place turnouts only in relatively flat areas where the rack is not needed. On systems where only the pinion is driven and the conventional rail wheels are idlers, such as the [[Dolderbahn]] in [[Zürich]], [[Štrbské Pleso railway station|Štrbské Pleso]] in [[Slovakia]] and the [[Schynige Platte]] rack railway, the rack must be continuous through the switch. The Dolderbahn switch works by bending all three rails, an operation that is performed every trip as the two trains pass in the middle. The Štrbské Pleso and Schynige Platte Strub rack system instead relies on a complex set of moving points which assemble the rack in the traversed direction and simultaneously clear the crossed direction conventional rails. In some rack systems, such as the [[Rack railway#Morgan|Morgan system]], where locomotives always have multiple driving pinions, it is possible to simplify turnouts by interrupting the rack rail, so long as the interruption is shorter than the spacing between the drive pinions on the locomotives.<ref>{{cite patent |country=US |number=772736 |inventor=John H. Morgan |title=Switching or Crossover Device for Traction Rack Rail Systems |pubdate=18 October 1904 }}</ref>

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=== Switch diamond ===
[[File:Switchdiamond.jpg|thumb|A switch diamond at a junction in the UK]]

Although not strictly speaking a turnout, a ''switch diamond'' is an active trackwork assembly used where the crossing angle between two tracks is too shallow for totally passive trackwork: the unguided sections of each rail would overlap. These vaguely resemble two standard points assembled very closely toe-to-toe. These would also often utilize [[swingnose crossing]]s at the outer ends to ensure complete wheel support in the same way as provided on shallow angle turnouts. In North America these are known as ''movable-point diamonds''. In the UK, where the angle of divergence is shallower than 1 in 8 (center-line measure) a switched diamond will be found rather than a passive or fixed diamond.

Such switches are usually implemented on the basis of increasing the safe crossing speed. Open blades impose a speed restriction, due to the potential of the crossing impact fracturing the rail as both wheels on each axle hit the crossing gaps almost simultaneously. Switched blades, as shown in the photograph, allow a much higher speed across the gap by providing an essentially continuous piece of rail across the gap on both sides.

The frog end of the switched crossing, despite still having a gap in one rail, is less problematic in this regard. The outer rail is still continuous, the wing rail (the part that turns out, after the frog gap) provides a gradual transition, and the check rail avoids the possibility of points splitting. This can be seen in how, under examination, the wing rail has a wider polished section, showing how the wheel load is transferred across the gap.

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=== Single-point switch ===
[[File:ON-TTC 20071110 StreetcarTrackSwitchPoint.jpg|thumb|left|A single-point switch on the [[Toronto streetcar system]]]]

Single point switches, known as Tongue and Plain Mate switches, are sometimes used on freight railways in slow speed operation in paved areas such as in ports. In the United States, they are regulated by provision 213.135(i) of the Federal Railroad Administration Track Safety Standards.

On streetcar ([[tram]]) systems using [[Tramway track#Grooved rail|grooved rail]]s, if the wheels on both sides of the car are connected by a rigid solid axle, only one switchpoint is needed to steer it onto one or the other track. The switchpoint will be on inside rail of the switch's curve route. When a streetcar enters the curve route of the switch, the wheel on the inside of the curve (the right side of the car on a right turn) is pulled into the turn, and through the axle, directs the wheel on the outside to also follow the curve.<ref name="Munro 2011">{{cite web |last=Munro |first=Steve |author-link=Steve Munro |date=10 November 2011 |url=https://stevemunro.ca/2011/11/10/ttc-unveils-new-streetcar-design-and-mockup/ |title=TTC Unveils New Streetcar Design and Mockup |access-date=2 October 2016 }}</ref> The outside wheel is supported for a short distance by its flange running in the groove.

Some low floor streetcar designs use split axles (a separate half-axle for the wheel on each side of the car). Such streetcars are unsuitable for use with single-point switches as there would be no mechanism to transfer the force from the inner to outer wheels at switches.<ref name="Munro 2011" />

A single-point switch is cheaper to build, especially in street trackage, as there is no need to link to a second switchpoint.<ref name="Munro 2011" />

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=== Rotary switch ===
[[File:Pilatus2.jpg|thumb|A [[Pilatus Railway]] turnout consisting of a bridge that rotates about its lengthwise [[axle]]]]

Rotary switches are sometimes used on cog railways to maintain alignment of the cog with two different tracks. They are used on the Pilatus Cog Railway to allow up-bound and down-bound trains to pass each other on a grade while sharing the remainder of the single track.

A rotary switch rotates about its long axis to present a track connection to a chosen set of tracks. Physically, it flips over (rotates about its long axis 180 degrees) to connect to the chosen set of tracks. Once the rotary switch is secured the train can proceed. Cog alignment is maintained in both positions.

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=== Temporary points ===
[[File:20180711 aiguillage californien at Bailli 2.jpg|thumb|Temporary or 'Californian' points installed on tramline 81 at the junction of Avenue Louise and Rue Bailli {{In lang|fr}}, a.k.a. Louisalaan and Baljuwstraat {{In lang|nl}}, [[Brussels]]]]

When a tram track is interrupted during repairs, a set of temporary points may be placed on top of existing track to allow trams to cross to the parallel track. These are known as {{lang|de|{{interlanguage link|Kletterweichen|de|Weiche_(Bahn)#Kletterweiche}}}} or {{lang|de|Auflegeweichen}} in German, {{lang|fr|aiguillages californiens}} in French, and {{lang|nl|{{interlanguage link|oplegwissels|nl|Wissel_(spoorweg)#Oplegwissels}}}}, {{lang|nl|klimwissels}} or {{lang|nl|Californische wissels}} in Dutch. They may be welded into place and allow trams to pass at walking pace.

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