Steel trestle with plate girder spans

A trestle is a bridge that consists of a large number of short spans, supported by splayed vertical elements and is usually for railroad use. Timber trestles were extensively used in the nineteenth century in mountainous areas. These were typically constructed using treated peeled logs as vertical elements with sawn timbers for bracing. Twentieth century construction has eliminated much of the need for trestles by using more extensive grading and tunneling. The trestle shown is a steel structure using relatively long plate girder spans. Trestle structures are also used for the approaches to bridges where required by the local topography.