When mountain biking, the lead of our group usually slows to tell any walkers how many more are following. Never thought about hand signaling it.
I'll have to try that on the next "Toy Run" with 100 Harleys behind me... Anyway.... I had to look twice at the OP, this a practice for off-roading / trails etc. Unfortunately, one often meets a bunch of dirt bikes or two quads, side by side, head on, coming around the corner - and this has happened more than once. However, I can see a use for this amongst the more considerate riders . Apart from getting old and decrepit, this is one reason I stopped riding the popular trails - Instead, I just got lost on old trails, miles from anywhere or anybody... but that's another story or two (i.e. how to get home when you've dumped the bike into a tree or rock...and your riding buddy isn't with you)
Don't know if this is universal but riders here passing each other in opposite lanes always give some sort of wave. Unless they're harley riders, who seem to generally hate everyone else. Also, in this same situation if a rider taps his helmet it means there's cops up ahead so slow down.
I find waving difficult as I’m wearing my heated gloves (about 10 months of the year because I’m very old & pathetic). If I wave with my right hand, the wires pull my left hand and I crash into the hedge. Not too bad because the throttle closed when I let go But waving with my left hand really cocks things up so if I wave at you be ready
