Not come across this but then I only weigh 17 stone.I'm sure I read somewhere that there were Weight in Motion system sensors set into the surface of some motorways- eg M25 and M6 -with cameras on overhead gantries to take number plate photos of overweight vehicles with a view to pulling them in further on. I know there was a big and successful trial some years ago and we have watched more overhead gantries put up, which we assume were part of this system.