We don't seem to do waving here, maybe it's the state of the roads.....
What we get is 'nodding'. Then there's the whole nodding hierarchy, should you nod at scooters? Should you nod at learners (not sure if it's normal, there's a whole seperate test for bikes, and learners have a big red L on a plate to show they are learning)? Should you nod at the waving harley rider?
Who knows?