We have low bridges in our area, too. Usually, the locals with van body trucks or people with campers are fairly alert with their units. There is no problem with the locals. Travelers are the problem. I'm a commercial truck driver and part time camper and are very much aware of what's overhead when traveling. Problems can arise when one gets off the beaten path and frustrated from being lost. One can lose sight of their height when tryinfg to get where they're going.
It's called PAY ATTENTION!!!! Always.