><<Of course, sometimes flashing hi-beams mean "Watch out, oncoming  drivers...
>there's a speed trap lurking around the next bend"... if only we  all knew
>how to flash our lights in morse code.>>
>
>here in NJ we turn the lights on and off to warn of a speed  trap...

It is difficult to tell if someone is flashing their high beams or just turning their lights on and off. So, Morse code would be superior.

Three sounds (bangs on the scuba tank; blasts of the ship's horn; etc.) I believe is the universal distress signal. Maybe flashing 3 times will be understood by some drivers that something's up. Especially if their (the guy headed for the trap) headlights are not on.

Dave