Bascule bridges have sections called "leaves" that rotate upward and away from the centerline of the river, providing clear passage for river traffic. “Bascule” is a French word for a see-saw or a balance scale, and a bascule bridge operates on the same principle of balancing two weights against each other, in this case the lift span and a heavy counter-weight.
Side by side on the Willamette River in downtown Portland, the Morrison and Burnside bridges are two examples of bascule bridges. These two bascule type bridges have a very clean, uncluttered look to them because the counterweights and operating machinery are located out of sight in the piers supporting the bridge. The Morrison Bridge is a Chicago-type bascule bridge and the Burnside Bridge is a Strauss-type bascule bridge.
The Broadway Bridge, located further downstream near the Rose Quarter, is an example of a Rall type bascule bridge. With this Rall type bascule, the counterweights are located above the roadway and much of the machinery is located in sheds, also above the roadway.