I know my truck will get under a 12, but I still watch my roof and tick 4-wheelers off by creeping at 15mph under a bridge that would destroy a van.
I bet he made the mistake they all do, floor it hoping it will magically come out without a dent.
My truck could fit under a 12, but not the trailer. Our tractors are 11'8" tall, and our tallest trailers are 12'6" tall.
Mines about that same height, maybe shorter. The only loads I've pulled that are taller than the cab are pipe or lumber, the the rare oversize specials we get once in a blue moon.