Railroad switch

As iron-railed plateways became more common in the eighteenth century, cast iron components were made to build switches with check rails.

[3] In 1797, John Curr described the system that he developed which used a single iron blade, hinged on a vertical pin that was tapered to lie against the plateway.

[6] Prior to the widespread availability of electricity, switches at heavily traveled junctions were operated from a signal box constructed near the tracks through an elaborate system of rods and levers.

Eventually, mechanical systems known as interlockings were introduced to make sure that a signal could only be set to allow a train to proceed over points when it was safe to do so.

On some low-traffic branch lines, in self-contained marshalling yards, or on heritage railways, switches may still have the earlier type of interlocking.

In a trailing-point movement (running through the switch in the wrong direction while they are set to turn off the track), the flanges on the wheels will force the points to the proper position.

On European high-speed lines, it is not uncommon to find switches where a speed of 200 km/h (124 mph) or more is allowed on the diverging branch.

Such approaches however, may not always be effective for extreme climates since these chemicals will be washed away over time, especially for heavily thrown switches that experience hundreds of throws daily.

In the United Kingdom points and crossings using chaired bullhead rail would be referred to using a letter and number combination.

In professional parlance, the term refers only to the movable rails and the entire mechanism is named turnout or points and crossings.

It can be assembled out of several appropriately cut and bent pieces of rail or can be a single casting of manganese steel.

There is also usually some kind of manual handle for operating the switch in emergencies, such as power failures, or for maintenance purposes.

The lever and its accompanying hardware is usually mounted to a pair of long ties (sleepers) that extend from the switch at the points.

In the United Kingdom, FPLs were common from an early date, due to laws being passed which forced the provision of FPLs for any routes traveled by passenger trains – it was, and still is, illegal for a passenger train to make a facing move over points without them being locked, either by a point lock, or temporarily clamped in one position or another.

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.

Likewise, it is called Engels(e) Wissel in Dutch and, occasionally, Engländer ("english one", literally "Englishman") in German.

This is normally used to allow access to sidings and improve safety by avoiding having switch blades facing the usual direction of traffic.

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.

Run-off points are used to protect main lines from stray or runaway cars, or from trains passing signals set at danger.

In some cases, catch points lead into a sand drag to safely stop the runaway vehicle, which may be traveling at speed.

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.

At dual gauge turntables, a similar arrangement is used to move the narrow-gauge track from one side to a central position.

The Dolderbahn switch works by bending all three rails, an operation that is performed every trip as the two trains pass in the middle.

These would also often utilize swingnose crossings at the outer ends to ensure complete wheel support in the same way as provided on shallow angle turnouts.

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.

On streetcar (tram) systems using grooved rails, 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.

Some low floor streetcar designs use split axles (a separate half-axle for the wheel on each side of the car).

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.

These are known as Kletterweichen [de] or Auflegeweichen in German, aiguillages californiens in French, and oplegwissels [nl], klimwissels or Californische wissels in Dutch.

In North America, turnouts are rated numerically, which represents the ratio of divergence per length as measured at the frog.

A right-hand railroad switch with point indicator pointing to right
Animated diagram of a right-hand railroad switch. Rail track A divides into two: track B (the straight track ) and track C (the diverging track ); note that the green line represents direction of travel only, the black lines represent fixed portions of track, and the red lines depict the moving components.
Large stations may have hundreds of normal and double switches (Frankfurt am Main main station, Germany).
Abt switch used in the 1895-built Dresden Funicular Railway (photo of 1985)
Control stand of a defunct railroad switch on the way from Pyin Oo Lwin to Goteik viaduct ( Myanmar )
The operation of a railroad switch. In this animation , the red track is the one traveled during a facing-point movement. The switch mechanism, shown in black, may be operated remotely using an electric motor or hand-operated lever or from a nearby ground frame .
Gas heating keeps a switch free from snow and ice.
Similarly, an electric forced-air heater can keep a switch free from snow and ice.
A low-speed #6 right-hand switch between a main line and a rail yard
This detail of a switch shows the pair of tapered moveable rails known as the switch points ( switch rails or point blades ).
A one-piece cast crossing . The shiny line crosses the rusty line. This North American "self-guarding cast manganese" component without guard rails has raised flanges on the crossing, which may bear on the face of the wheel as it passes through.
The frog (left) and guard rail (right) of a switch
The switch motor (in this case an electric motor) and associated mechanism used to operate this switch can be seen to the right in the picture.
An example of a mechanism used at a switch. The two points are linked together with a throw bar (also known as a stretcher bar). The throw bar extends to the lever on the near side of the track, which is used to throw the switch . This is an example of a low switch stand, used at locations where there is not sufficient clearance for a tall switch stand. This particular stand is designed to be trailed through by rolling stock, which will cause the points to become lined for the route that the wheels have passed through. It has a reflectorized target.
The manual switch of track drive manufactured by Walter Hoene, the port of Gdańsk before 1945, on the site of the former fuel depot
A set of points on the Strathspey Railway in Scotland. The facing point lock in the middle will need to be withdrawn using the blue lever (behind) on the left before the points themselves can be moved using the black lever (front). Once the points have been moved the lock will be pushed in again with the blue lever to lock the points in position.
A double switch, or double slip—the points are set to connect the upper left and lower right tracks.
A double, outside slip in Heidelberg main station
A double crossover at Richthof between Kirchheim and Langenschwarz stations on the Hanover–Würzburg high-speed railway
A scissors crossover: two pairs of switches linking two tracks to each other in both directions
Closeup of a stub switch in Pennsylvania
A narrow-gauge stub switch —this switch has an additional piece of movable rail instead of a frog.
A three-way stub switch at Sheepscot station on the Wiscasset, Waterville and Farmington Railway
A narrow-gauge plate switch
A wye switch on the mainline, leading to a single-track bridge, near Ravenstein, Netherlands
Trap points at the exit from a yard
A dual-gauge switch in Japan
A switch diamond at a junction in the UK
A single-point switch on the Toronto streetcar system
A Pilatus Railway turnout consisting of a bridge that rotates about its lengthwise axle
Temporary or 'Californian' points installed on tramline 81 at the junction of Avenue Louise and Rue Bailli (in French) , a.k.a. Louisalaan and Baljuwstraat (in Dutch) , Brussels
A railroad switch in Wazir Mansion Station , Karachi, Pakistan
Transport of switches by rail creates problems as they are so long and wide.