Does anyone know a widely accepted signal to other riders that there is law enforcement in the area. I've seen, and been using, the hand twirled over the head (cop's twirling/flashing red light). But, I'm not sure the message always gets across. I've had guys do the hand pump, down low-palm down, but this can also just mean slow down for whatever hazard. A guy posted the other day that a "helmet pat" is what he uses. Is there a consensus?