Often motorist do something that makes me wish they had stayed at home, but they also frequently do nice things too. Like slowing down to let me in to the lane, or making sure that they overtake with plenty of room etc...
Is there an unambiguous gesture that means "thank you"? I don't want to confuse people about my intentions (by using a gesture that could be interpreted as something else) but it would be nice to show appreciation.
I use a sort of wave, raising my hand but with no movement in it (so not a 'Hey buddy' or 'I need help' side to side movement).... it works on my bicycle, on my motorcycle, and while driving a vehicle. It's got somewhat of a dual purpose: acknowledgement that I did something wrong, and/or 'thanks for letting me in' gratitude gesture.
This is the same gesture I seem to get from many other people. There's no side/side or waving motion (would be more like "Hi!"), just a hand up, fingers together, "Thanks/Sorry".
A polite nod, wave or smile usually suffices.
It doesn't need to be much, where I live in the UK raising one or two fingers from the steering wheel is plenty when driving. Not sure about down south, I've heard it's a fairly local thing, but I don't imagine it being too different.
This would generally come down to you locality as some cultures would consider certain gestures rude. I guess there isn't a universal sign for thank you, but in most cultures I think a wave of the hand (more of a raise the hand and show the palm slightly) with a courteous smile or nod would do the trick.
I tend to vary between a wave of the hand or a thumbs up followed by a wave of the hand. A smile always tends to convey gratitude, but that depends on whether you can be seen clearly or not.
One thing we do in France is to take off one of your legs from the pedal and put it on the side (usually your leg on the side of the motorist you want to thank). Which looks a little like this :
The fact that you take the time to do it and stop a little your effort by taking off your feet from the pedal is usually well considered by motorists.
Motorists (I'm both a cyclist and motorist) use to salute with each other making a "V" sign with the index and middle fingers of the hand with the palm forward. At least it's that way in southern Europe, don't know in other parts of the world. They would understand that with as a symbol of empathy to them.
I show the palm facing the driver. This also means "stop" but yes, please do not drive on me while I am using your courtesy now (is Switzerland some drivers are so careful they give you priority regardless of the traffic code that would otherwise apply).
A summary of than you signals can be found in this New York Times article.
