I nearly took the roof off a (hired) 7.5 tonner. The insurance specifically did not cover this either, so I'd have had to pay the full cost. I had carefully worked out there were no bridges on my route, so put that particular worry out of my mind whilst I concentrated on driving this huge truck - which us oldies are allowed to drive on our car licences. Unfortunately I took a wrong turn in the fog, and suddenly remembered half way under a low bridge. The label in the cab said 11' 9" or something, and in my mirror, the sign on the bridge said 11' something-inches. Must have been very close !