i do a similar thing, but i also keep a breaking bar down the side of the drivers seat. i'd never hit anyone in the head with it, but i'd sure as hell make sure they wouldn't be running off before the police get there (and yes i know about reasonable force, thats why i won't be repeatedly kicking them or hitting them once they've gone down.)
i used to be a door man in coventry and my size tends to be a big enough deterant as does the shaved head and beard.
i am very placid by the way,it takes a lot to get me wrlyed and i learnt a long time ago to be defenseive not offensive.
+1. Being 6'2" and 17Stone helps me stop any trouble before it starts