If you want truly autonomous vehicles then they need to be able to communicate with each other. How else will they avoid each other/drive in the most optimal way? This is why I think autonomous vehicles is 15 years away at earliest. The "infrastructure + majority of the vehicles on the road being autonomous" combo is not happening anytime soon.
They don't need 5G to talk to each other.
Routing itself we already have. That's text (non visual encoded data) and we already have that. You don't need 5G speeds for that.
Traffic routing is an algorithmically difficult problem not a network capacity problem and we already know how to route well enough.
Is your question how do two vehicles avoid colliding with each other? The answer to that is: not over the Internet.
Believe that the way to avoid an impending collision is to ask questions over a non-guaranteed medium of communication brehs.
That would be like phoning someone to get advice on how to dodge a bullet.
As an aside collision avoidance is far more likely to be agreed in advance i.e. model A adopts public plan 1 model B adopts public plan 2 then both A and B can predict (to some degree) what the other car will do.
The real answer to all of this waffling is video. 5G allows for real-time video communication and you don't
need that to let cars drive themselves.