I had the wonderful experience to be in a car in the traffic of Mumbai. I felt that something was different ’cause everyone was extensively using his car horn.
In Italy (especially in the north), after you use the horn, there is a chance that you start “talking” with the other driver. Here it’s not the case: everyone is really comfortable with this.
And than I understood: they use horns in a collaborative way. It’s like a storm of birds: they use it to signal their position on the road. It’s like a ‘positioning sensor’.
You start moving on another line, you might hear a single horn saying “I’m here but you can stay” or a double that means “no no no .. it’s me here!”