[2] In American English, the term is synonymous with drawbridge, and the latter is the common term, but drawbridge can be limited to the narrower, historical definition used in some other forms of English, in which drawbridge refers to only a specific type of moveable bridge often found in castles.
An advantage of making bridges moveable is the lower cost, due to the absence of high piers and long approaches.
Generally, the bridges are powered by electric motors, whether operating winches, gearing, or hydraulic pistons.
While moveable bridges in their entirety may be quite long, the length of the moveable portion is restricted by engineering and cost considerations to a few hundred feet.
In the United States,[4] regulations governing the operation of moveable bridges (referred to as drawbridges)[5] – for example, hours of operation and how much advance notice must be given by water traffic – are listed in Title 33 of the Code of Federal Regulations;[6] temporary deviations are published in the Coast Guard's Local Notice to Mariners.