movable bridge
A bridge of any form which is capable of controlled movement in order to lift or remove its span.
A movable bridge is a bridge which can clear a path under it, or switch its direction, by means of controlled movement around some point or along some axis. Movable bridges can swing around an endpoint or midpoint, can be lifted vertically at one or both ends, or can pivot up at one or both ends.
The opening action is a controlled change in the position or shape of a span. It can provide passage for traffic below or align the bridge with a different route.
Different mechanisms raise, lower, rotate, slide, or fold the crossing. A submersible span moves downward into the water; a fixed bridge temporarily covered by flooding has no corresponding controlled opening action.