A switcher or shunter (Great Britain: shunter; Australia: shunter or yar pilot; USA: switcher (or switch engine), except Pennsylvania Railroad: shifter) is a small railroad locomotive intended not for moving trains over long distances but rather for assembling trains ready for a road locomotive to take over, disassembling a train that has been brought in, and generally moving railroad cars around - a process usually known as switching (UK: shunting). They do this in classification yards. Switchers may also make short transfer runs and even be the only motive power on branch lines.