Railroad Switch/Turn Out/Rail Turnout/Railroad Turnout/Railway Switch/Railway Turnout/Turnouts in Railways

Arailroad switch(AE),turnout, or [set of]points(CE) is a mechanical installation enablingrailwaytrains to be guided from onetrackto another, such as at arailway junctionor where aspurorsidingbranches off.

The most common type of switch consists of a pair of linked tapering rails, known aspoints(switch railsorpoint blades), lying between the diverging outer rails (thestock rails). These points can be moved laterally into one of two positions to direct atraincoming from the point blades toward the straight path or the diverging path. A train moving from the narrow end toward the point blades (i.e. it will be directed to one of the two paths, depending on the position of the points) is said to be executing afacing-point movement.

For many types of switch, a train coming from either of the converging directions will pass through the switch regardless of the position of the points, as the vehicle's wheels will force the points to move. Passage through a switch in this direction is known as atrailing-point movementand switches that allow this type of movement are calledtrailable switches.

A switch generally has a straight "through" track (such as the main-line) and a diverging route. The handedness of the installation is described by the side that the diverging track leaves.Right-hand switcheshave a diverging path to the right of the straight track, when coming from the point blades, and aleft-handed switchhas the diverging track leaving to the opposite side. In many cases, such as rail yards, many switches can be found in a short section of track, sometimes with switches going both to the right and left (although it is better to keep these separated as much as feasible). Sometimes a switch merely divides one track into two; at others, it serves as a connection between two or more parallel tracks, allowing a train toswitchbetween them. In many cases, where a switch is supplied to leave a track, a second is supplied to allow the train to reenter the track some distance down the line; this allows the track to serve as a siding, allowing a train to get off the track to allow traffic to pass (this siding can either be a dedicated short length of track, or formed from a section of a second, continuous, parallel line), and also allows trains coming from either direction to switch between lines; otherwise, the only way for a train coming from the opposite direction to use a switch would be to stop, and reverse through the switch onto the other line, and then continue forwards (or stop, if it is being used as a siding).

　　Astraight trackis not always present; for example, both tracks may curve, one to the left and one to the right (such as for awye switch), or both tracks may curve, with differingradii, while still in the same direction. Switches consume a relatively high proportion of a railway maintenance budget.

Railway Turnout Dimensions