It's quite possible that they don't actually take account of there being any person in the cars. I had my car spat onto once - sun roof being open. They only got the windscreen, thank goodness, and that it was only spit. I think that was the challenge of the hole. I made a point for a while of changing lane if possible when I saw someone on the bridge.

And I got hit by an egg thrown from a van oassing me on an ordinary road in Gloucestershire. It damaged the paintwork. Combined speed less than 60, I think.

Penny