If you think it is a serious issue day in and out then I would suggest fitting a camera or a mobile phone mount and videoing what happens. If your camera is good enough you can pick out plates too after the event
If nothing happens then delete the film (or move it off to another device) and repeat - kind of like a car black box.
There was a long thread on tailgaters a while ago - it got a little rough including dropping stones, marbles or spraying stuff - all sorts.
http://ecomodder.com/forum/showthrea...ters-5214.html
Personally I try and find something slow to follow, then people know you are not in a rush. Also on single lane roads leave a gap so people passing can pull in between you and the vehicle in front - when I drove for speed one of the most frustrating things was the challenge of having to pass all 3 in front of me vs just one at a time.
And finally, just let the others "win" their race - who cares, you are fighting physics and not other drivers.