A turnout, or railroad switch, is a track arrangement that allows one set of rails to connect with another. The mechanism consists of a pair of moveable tapered sections of track, known as switch points, which can be pushed into one of two positions, enabling a train to remain on its course or to divert to another line. A common function of a switch is to control access to a siding—a length of track that briefly diverges from a line, allowing a train to be temporarily housed while another train passes by. Sidings can also be used for storing, loading, and unloading cars, and for holding maintenance equipment.
Sharing the line
Sidings allow multiple trains to run on the same routes. They are used primarily at stations to let trains vacate the main line so that express services can pass through, or on longer stretches of track to enable freight trains to be passed by faster passenger services. Safety signals ensure that only one train occupies a siding at any one time.
The key component of a turnout is the points mechanism, which was invented by English engineer Charles Fox in 1832. The mechanism is activated by a lever connected to a pull rod, which moves the points from one track to the next. Most points are now electrically operated, but pneumatic versions are also used on some networks, particularly underground lines.