Track components

Railways are highly complex feats of engineering, with many hours of planning and forethought required for a successful outcome. The first component of a railway is the route, which is planned to provide the least resistance in terms of gradient and engineering works. As such, the track bed is heavily engineered to provide, where possible, a level surface. As such, embankments are constructed to support the track and to provide a compromise in terms of the route's average elevation. With this in mind, sundry structures such as bridges and viaducts are constructed in an attempt to maintain the railway's elevation, and gradients are kept within manageable constraints. Where such structures are not always justified, such as in hilly terrain where routes may require long detours to avoid such features, a cutting or tunnel is dug or bored through the obstacle. Once the sundry engineering works are completed, a bed of stone (ballast) is laid over the compacted track bed to enhance drainage around the ties and evenly distribute pressure over a wider area, locking the track-work in place. Crushed stone is firmly tamped to prevent further settling and to lock the stones. Minor water courses are channeled through pipes (culverts) before the grade is raised

The base of the trackage consists of treated wood, concrete or steel ties (sleepers). These ensure the proper distance between the rails (known as the track's "gauge"). Traditional US practice with wood sleepers is to anchor the rail structure to the road bed through the use of baseplates. These are attached to the top of the ties to provide a secure housing for the flat bottomed rails. After placement of the rail atop the plate, spikes are driven through holes in the plate and into the tie where they are held by friction. The top of the spike has a head that clamps the rail. As an alternative, lag bolts can be used to retain the clamps, which is preferred since screws are less likely to loosen. Traditional practice in the UK was to screw cast iron 'chairs' to wooden sleepers. These chairs loosely hold bullhead rail which is then secured by a wood or steel 'key' wedged between the side of the rail and the chair. With concrete or steel sleepers fixings are built into the sleeper to which flat bottom rail is attached with sprung steel clips.