The best thing he can do is put a camera on his dashboard, a lot of people are doing this now and it does work, the next time you get some asshole pulling the same thing you can film them and they won't be able to claim you were doing something different.
as a fellow driver i can understand it but as some people in here are saying "im a safe driver" no everybody makes a mistake and those that think there safe often get a nasty surprise
as for people driving "at the speed limit" this only really protects against hitting smaller things such as people 2 cars dont make much difference at 30 or 40mph
and ontop of that old people are the least likely to crash.... you know why? because they drive so slow they cause other people confusion and cause others to crash. just sit at a roundabout for an hour on a busy road and youll see both women and old people are the most dangerous people on the road, when a guys in a car you expect him to be a dick so it easier to plan for when a woman or old persons in a car theres many many more options to consider.
back on topic if you dont get anything from the insurance sorted post his plates online and watch his life slowly get worse