I remember when I first moved to Japan that my friends and I got off of our bikes and moved to the side of the road to let a car pass (it was a very small road). The driver honked as they went by, and the other American and I thought they were being rude. Honking in the US usually means, "get outta the way!" Our Japanese friend corrected us, telling us that two quick honks meant "thank you." I was blown away that such a thing existed!