Nearest I've come to it was when I was tailgating a car coming into a city with my wife on the back. Yeah, I know, it was irresponsible but.... Anyway, we both saw the hubcap appear from underneath the car in front at the same time. The only choice I had at that time was to over it. No harm done, but I can imagine that I would have lost a few fillings if it had of been a ladder!!