> There are three basic types of draw bridge. The most common is the kind where one or both sides rise to a near vertical position allowing a tall ship to pass.
>
> Sometimes a section of the bridge is on a turntable so that it can rotate 90 degrees allowing ships to pass on both sides.
>
> Another type of drawbridge is the vertical lift where a section between two towers rises high enough to allow ships to pass underneath. The Tower Bridge in London is one of those.
>
> Without draw bridges, Hollywood car chases would be a lot less interesting.
> Howard

It occurs to me that there's also a 4th type of opening bridge, though I only know of one example: The Gateshead Millenum Bridge in northern England. It's earned the nickname "The Blinking Eye Bridge" because of the way it pivots to let ships through.

A picture of it closed:
http://en.wikipedia.org/wiki/Image:Millenium_bridge_close.jpg

And open:
http://www.gifford.uk.com/news/2001_11_01/01-gateshead-B.jpg

Looks good, no?

wintermute