In the state of Washington we had a bridge across Hood Canal. It needed work so they hired a contractor to do the job then put a charge on the bridge until the contractor had been paid off (with interest). When the bridge was paid for the state didn't remove the charge - until they got sued, and lost. We have the same thing going on, right now, on the Narrows Bridge. As far as I know the same deal holds, I have no idea if its paid off yet or not. I do know that they keep raising the rates to use the bridge although it only on one way. I suspect the state continues to pay the contractor for their work and equally suspect that the raises are for the coffers of the state. OH, the reason its only charge for one way is because the bridge was expanded, by 4 lanes, all of which are used to go one way.
It will be interesting to see what happens when somebody figures out the bridge is paid for and the state has turned the bridge into a cash cow.