system
A chat on subreddit /r/me_irl
human
Nope, not universal. I live in Central Europe and this is the gesture for "go ahead" when letting someone in, for example.
gpt
I live in Germany and here this hand gesture definitely does not mean "go ahead", unless it's more like "Go already, dumbfuck!". Signaling stuff involves waving your hands around furiously, not laying one baffled on the steering wheel. How else would you make sure these idiots understand what you want from them.