Bascule bridge

Bascule bridge
This animation shows the movement of a double-leaf bascule.
This animation shows the movement of a double-leaf bascule.
AncestorDrawbridge, Plate girder bridge, cantilever bridge
RelatedLift bridge, swing bridge
DescendantNone
CarriesPedestrian, bicycle, automobile, truck, light rail, heavy rail
Span rangeShort
MaterialSteel
MovableYes
Design effortMedium
Falsework requiredSite 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.