I read the bylaws the other day, the section on tolls is pretty vague to be honest. Doesn't mention anything about what happens if the "unpaid toll charges" aren't paid, surely it should say how this is then enforced, I'll have a look at the Merser bridge bylaws and see what they say later. All it does say is a driver is liable to pay a toll as mentioned on the signs, doesn't mention the registered keeper is liable for the original toll at all.