- A bridge is a structure built to span a gorge, valley, road, railroad track, river, body of water, or any other physical obstacle.
A bridge is designed for trains, pedestrian or road traffic, a pipeline or waterway for water transport or barge traffic.
An aqueduct is a bridge that carries water, resembling a viaduct, which is a bridge that connects points of equal height.
A road-rail bridge carries both road and rail traffic.
A bridge’s structural efficiency may be considered to be the ratio of load carried to bridge mass, given a specific set of material types.
A bridge’s economic efficiency will be site and traffic dependent, the ratio of savings by having a bridge (instead of, for example, a ferry, or a longer road route) compared to its cost.
