> This, of course, will require some kind of centralized control over entire convoys, and a way to coordinate them. Railways and airways definitely can offer examples of how to handle that.

Not at all. A simple peer to peer protocol based on proximity and mixing in traffic data distributed like the national weather service will do just fine.

These convoys seem like a perfect example of swarm algorithms fitting well where you don’t need a central coordinator.

Within a convoy, yes. Between convoys, a dispatcher service could be beneficial, distributed and federated, again, like air traffic controllers and railway dispatchers. The same self-driving car companies that produce the software and require subscription could offer it.