The railway bridge across the river in my town now has a lift span to allow barge traffic to pass. However, when I was a child, the bridge had a swing span. The span actually turned on a center axis away from the rails to let the barges through. It was determined a lift span was a better option, but I remember how odd it looked to see part of the bridge shifted away from the rest of the rails.
The river is about half a mile across, plus backwater, so the railway bridge is a long one. It's been completely replaced over the years, but since it's part of two major railroads that merge across the river, I don't see it going anywhere any time soon.