A bascule bridge moves vertically by rotating upward from one pier. Like the vertical lift bridge, a bascule bridge has counterweights that help motors move the multi-ton span. The bridge above, over the Savannah River in downtown Augusta, is a rolling lift bascule. Its counterweights can be seen in the top right of the photo.
The days when these particular movable bridges actually moved may be coming to an end. Today the Omaha bridge stays in the up position because the railroad it carried has been abandoned. The bridges at Lumber City and Augusta still carry trains but barge and steamboat traffic has vanished so there is seldom a reason for these bridges to move.