|Source: Wikimedia Commons
It's probably overkill how entertained I am by this: Google has taught their self-driving cars the etiquette of honking. They now know to give a couple short "Did you see me here?" honks to someone backing up towards them, or a long, sustained honk for a more urgent situation.
So, basically, these cars will be better at honking than you and me.
Source: The Verge