I don't think I've ever seen riders in continental races using hand signals.
....but that might be because there aren't any potholes on the continent. Villages that have paid enough to get the TDF through will also be made to patch up their roads before the race.
Yes i can see that where being heard is a problem then hand signals are the better alternative. Makes sense. Thanks.Hand signals are better from the rider at the front if the group going fairly fast - you just dont hear it otherwise with the windnoise (a shout from the rear can be heard better). It is quite easy to see the signals - and the signal also tells you where the hazard is because you wont always be wanting to move to the outside but go on the inside.