Originally Posted by
CB HI
This, plus, if you get the feeling that a motorist is about to pull such a bonehead move, put your left arm straight out with the palm facing behind (and having a blinkie on that left wrist can help).
If the driver is willing to "pull such a bonehead move" what's to say he'll stop for an outstretched hand. Better to keep your hands safely on the bars and not risk smacking a mirror. Using a helmet cam to document anything really dangerous and illegal might be helpful though.