Let's say "Joe" is going a little faster than the speed limit going up the S2S toward Squamish on his sportbike. Coming the other direction is "Bill" also riding a sportbike. Bill has just seen a speed trap three turns behind him pointed in the other direction.
Is there a signal that "Bill" would most commonly use (or be understood by) to tell "Joe" that he is rushing towards a speed trap? I.E. how does one give or receive the message?
I am thinking maybe high beams ... but on a bike its often so hard to see. Is there a hand signal?