Sidings are placed at regular intervals along single-track mainlines. Generally the length of the longest train on the route, a siding allows a train to pull off and wait for an oncoming train, or a faster train behind it, to pass.
Passenger stations that are not an end destination on a route are often serviced by one or two sidings, the number depending on the traffic along the mainline.
When the tracks from two railroad companies intersect, they cross at a junction. An interchange siding, accessible from both mainlines, allows one railroad to leave cars at the siding to be picked up by a train from the other railroad.
A siding can be used by a local freight train to move freight cars to and from industrial loading docks along dead-end spurs running off the siding. Cars can also be left on the siding for unloading or later pickup.
Industrial sidings are not maintained at the same level as mainlines, and as shipping demands decrease, the tracks fall into disrepair. When officially abandoned, the switches to the siding will be removed, although the tracks may remain.
