Autonomous Car - Close proximity communication protocol for Cars ?

Driver-less cars are fascinating thing of this century, few companies like mobileeye, google are already pioneering this space. Tesla's autonous parking, lane switching to add to the WoW!!!

Of all it's interesting how in a 4 way stop the technology just on one car can safely navigate everybody? Isn't there suppose to be a low frequency and range based communication protocol between cars could control the outcome better ?

Even if one of the car makes the mistake, the other car does the defensive driving. How about for a change :)...

Think of the possibilities, if you are traveling with your friends and driver-less, you don't have to follow them. The car communicates with the each other and locks the route and you can get to continue with book you are reading or the movie you are watching and you don't have to stop for coffee in 2 different shop. It's a cool travel experience with group tagging along with different cars.