It's not an impossible problem to solve, but I have not heard of any efforts to create a car-to-car or car-to-road communications protocol and infrastructure that would be cross-manufacturer and/or internationally approved.

In my opinion, before such a mechanism exists, autonomous cars will only work as long as the majority of cars are driven by humans. I will change my opinion when I see a demonstration of a city (or city-like test site) traffic where all or the majority of cars are autonomous.