Vehicle: Car: Communication: Gesture
Cartop Animatronic Motorcyclist   (+2)  [vote for, against]
I'm just waving...

When on the motorcycle I engage in the two most common hand signals.

The first is the wave, in which the initiator poses the question to a motorcyclist going the other way " Are you having as much fun as I am ? " and the responder signals " I sure am ".

The other is the hand touched to the helmet, signifying " There's a cop ahead of you ".

While driving my car I regret not being able to tell my two wheeled brethren that there's speed enforcement ahead. So this roof mounted simulated cyclist (from the waist up) would deliver those two signals from the touch of a button inside the car.
-- normzone, Mar 19 2015

A more intensive version that predates this less flexible application Waldomobile
[normzone, Mar 19 2015]

There are a couple of other hand signals bikers use, but these are almost exclusively reserved for drivers of vehicles with four or more wheels, the small remainder being shared between pedal cyclists and pedestrians ...

-- 8th of 7, Mar 19 2015

Around here we just flash our high-beams to indicate speed traps, rock slides, or wildlife.
It would be nice to be able to specify.
-- 2 fries shy of a happy meal, Mar 19 2015

The signal hererabouts is left hand out, palm down, patting downward. Four wheels and above flash lights. Both mean slow down. Could mean cop ahead or other reason to slow down. Hand touching head means your headlight is out.
-- cudgel, Mar 19 2015

random, halfbakery