It's amazing how some drivers like to behave in such a situation. Something I do when a driver passes me and shouts their usual abuse is to pull up behind them at the next set of traffic lights and just sit at the rear of the vehicle and watch them squirm. It works every time! I'm not a big guy by any means (62kg or so), but apparently it's enough to frighten the crap out of them. I never fail to get a good laugh out of that one!