Drawbridge (American English)
A moveable bridge, or movable bridge (common alternative spelling in American English), is a bridge that moves to allow passage (usually) for boats or barges. In American English, moveable bridge and drawbridge are synonymous, 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 only to a specific type of moveable bridge.
An advantage of making bridges moveable is the lower cost, due to the absence of high piers and long approaches. The principal disadvantage is that the traffic on the bridge must be halted when it is opened for passages. For seldom-used railroad bridges over busy channels, the bridge may be left open and then closed for train passages. For small bridges, bridge movement may be enabled without the need for an engine. Some bridges are operated by the users, especially those with a boat, others by a bridgeman (or bridge tender); a few remotely using video-cameras and loudspeakers. 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.
There are often traffic lights for the road and water traffic, and moving barriers for the road traffic.
In the United States, regulations governing the operation of moveable bridges (referred to as drawbridges) – 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; temporary deviations are published in the Coast Guard's Local Notice to Mariners.
...
Wikipedia