If i'm 100km out of the CBD i'll wave at all the Discos and Defenders and get about a 50-60% response. If i'm on mountain or outback roads i'll pretty well wave at any 4wd the goes past and get a 70% response.
When i lived in Sydney and had the DSCVRY number plate, i would get a honk and a wave from about 80% of other Disco drivers no matter where i was :)
I also love the fact that you can say hello to most people in small country towns and still get a good response back...try it in the city and people look at you like you are an idiot.
I tested this while spending two days taking photos of bridges that cross over the Yarra River. Whenever i said hello to anyone approaching me i swear about 90% of people looked at me weird and then started walking away from me quicker than they approached me, they also glanced back occasionally to make sure i wasn't following them. The few that did return my greeting would have been mostly aged over 50.

