In message , at 13:57:00 on Fri, 6 May 2016,
Basil Jet remarked:
surely the point of these crashes is that the bloke thinks that even
though the sign/detector/water curtain thinks that he's too high for
the bridge/tunnel, he thinks that he'll squeeze through with half an
inch to spare, and a lot of the time he'll be right.

It's much more likely they just forget what they are driving (how high
etc).
--
Roland Perry