definition
strict definition
rolling bascule bridge
A movable bridge whose span rises as large gears roll along a shoreline rack, without a fixed hinge.
A rolling bascule bridge is an openable bridge whose span rises when large gears at the shoreline roll on a rack. Although the opening motion of this type is similar to a drawbridge or a bascule bridge, it operates without a hinge.
The support rolls along the rack while the span rises. The combined rolling and lifting motion differs from turning around a stationary hinge.
Its raised appearance can resemble a drawbridge or a hinged bascule bridge. The rack-guided rolling mechanism, rather than the open silhouette alone, establishes this form.