A
siding, in
rail terminology, is a low-speed track section distinct from a running line or through route such as a
main line or
branch line or
spur. It may connect to through track or to other sidings at either end. Sidings often have lighter rails, meant for lower speed or less heavy traffic, and few, if any, signals. Sidings connected at both ends to a running line are commonly known as
loops; otherwise they are known as
single-ended sidings or
dead end sidings, or (if short)
stubs.