What the OP missed: highways with traffic jams caused by breakdowns somewhere in miles-long platoons of self-driving shipping containers that block entry/exit l

What the OP missed: highways with traffic jams caused by breakdowns somewhere in miles-long platoons of self-driving shipping containers that block entry/exit lanes (because there's no such thing as a perfect drive train, and cost competition will ensure that the cheapest prevail over the best, and of course they'll use drafting and drive nose-to-tail to reduce energy costs, because the failure mode is "only" a breakdown, and the inconvenience and cost is someone else's problem).