Viaduct

A viaduct is a bridge composed of several small spans for crossing a valley or a gorge. The term viaduct is derived from the Latin via for road and ducere, to lead. The ancient Romans did not use the term; it is a modern derivation from an analogy with aqueduct. Like the Roman aqueducts, many early viaducts comprised a series of arches of roughly equal length. Viaducts may span land or water or both.

Usage

The longest viaduct in antiquity may have been the Pont Serme which crossed wide marshes in southern France. In Romance languages, the word viaduct refers to a bridge which spans only land. A bridge spanning water is called ponte.

Over land

Viaducts are commonly used in many cities that are railroad centers, such as Chicago, Atlanta, Birmingham, London and Manchester. These viaducts cross the large railroad yards that are needed for freight trains there, and also cross the multi-track railroad lines that are needed for heavy railroad traffic. These viaducts keep highway and city street traffic from having to be continually interrupted by the train traffic. Likewise, some viaducts carry railroads over large valleys, or they carry railroads over cities with many cross-streets and avenues.