Each time I came down from Scotland I usually ended up driving
through the dark. Loads of times I'd see in my mirrors or
ahead what looked like somebody flashing me. Or maybe they
were just riding over a bump in the road. Or something. I ended
up getting out and checking all the lights every time I filled
up with petrol. Never found a problem. I now always assume
a flashing light is actually the car going over a bump.

JGH