BRIDGE COMBINATIONS

Table:	Arch	Cable Stay	Cantilever Truss
Pulley Draw	Would work if provided another way for bridge to be supported when roadbed is opened.	Would only work at one end of the bridge but could be done.	Would work but is a common design and would appear boring.
Retractable w/ Gears	Same as above	Would work at opposite end of the bridge.	Would work well in the middle of the bridge, provided the side supports then be rotated out of place.
Hinged Fold w/ Gears	Same as above	Would also only work at the end of the bridge because the cables cannot be broken to allow movement.	Would work well if the side trusses of the bridge could somehow be easily folded.

Images:

Cable Stay Drawbridge with opening in the middle.

Cable Stay Cantilever Combo with Opening in the middle.