Track and support

Its job in the system

Track is a structure, not just two steel lines. Wheels apply forces to rails; those forces pass through supports into the structure or ground below. The arrangement must preserve the spacing and alignment the train requires while carrying repeated loads. A line that looks straight on a map can still have important gradients, curves and local speed constraints.

How it works

On ballasted track, sleepers or ties support the rails and maintain their spacing. Fastenings connect the rails to those supports, and the stone ballast helps distribute loads and hold the track in place. Other installations use concrete slab track. The two approaches have different construction and maintenance characteristics; neither removes the need to monitor geometry and condition.

Water and temperature connect the railway to its surroundings. Drainage affects the stability of the supporting ground and ballast. Steel rails also respond to temperature changes, which must be accommodated by the track’s design and maintenance. The engineering response is specific to the installation, rather than a universal temperature at which every railway must stop.

What it connects to

The track supports the train, contains points at route changes and may also participate in electrical return or train detection. Work on one of these functions can affect the others. Inspection and maintenance need protected time and access, so the usable timetable must leave opportunities to maintain the infrastructure that makes the service possible.

Different places, different designs

Underground, elevated and surface railways use different supporting structures. Ballast is common, but some tunnels and bridges use slab or other track forms. This family follows a conventional steel-wheel railway; rubber-tyred metro systems and street-running trams introduce additional interfaces. Local operating and engineering standards determine the details.