Bascule bridge

Bascule bridge

This animation shows the movement of a double-leaf bascule.
Ancestor	Drawbridge, Plate girder bridge, cantilever bridge
Related	Lift bridge, swing bridge
Descendant	None
Carries	Pedestrian, bicycle, automobile, truck, light rail, heavy rail
Span range	Short
Material	Steel
Movable	Yes
Design effort	Medium
Falsework required	Site and prefabrication specific

A bascule bridge (also referred to as a drawbridge or a lifting bridge) is a moveable bridge with a counterweight that continuously balances a span, or leaf, throughout its upward swing to provide clearance for boat traffic. It may be single- or double-leafed.

The name comes from the French term for balance scale, which employs the same principle. Bascule bridges are the most common type of movable span because they open quickly and require relatively little energy to operate, while providing the possibility for unlimited vertical clearance for marine traffic.