Switch terminology

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 lever or from a nearby ground frame.

A railroad switch, turnout or [set of] points is a mechanical installation enabling railway trains to be guided from one track to another at a railway junction.

The switch consists of the pair of linked tapering rails, known as points (switch rails or point blades), lying between the diverging outer rails (the stock rails). These points can be moved laterally into one of two positions so as to determine whether a train coming from the narrow end will be led towards the straight path or towards the diverging path. A train moving from the narrow end towards the point blades is said to be executing a facing-point movement.

Unless the switch is locked, a train coming from either of the converging directs will pass through the points onto the narrow end, 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 a trailing-point movement.

In a trailing-point movement, the wheels will force the points to the proper position. This is sometimes known as running through the switch. If the points are rigidly connected to the switch control mechanism, the control mechanism's linkages may be bent, requiring repair before the switch is again usable. For this reason, switches are normally set to the proper position before performing a trailing-point movement.

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 switches have a diverging path to the right of the straight track, when coming from the narrow end and a left-handed switch has the diverging track leaving to the opposite side.

A straight track is not always present; for example, both tracks may curve, one to the left and one to the right (such as for a Wye Switch) or both tracks may curve, with differing radii, in the same direction.