Safe driving for a human also depends heavily on predictable behavior of others. If that's an important metric, it seems like the optimal solution is a single

Safe driving for a human also depends heavily on predictable behavior of others. If that's an important metric, it seems like the optimal solution is a single self-driving system with a monopoly on the market... that way each and every driver is predictable, correct? I guess I don't understand your argument. We put faulty humans in control of a ton of steel/battery in the same system all the time; humans have the disadvantage that when lessons are learned, they aren't transferrable without great amounts of effort. Self-driving systems can share learnings across the whole fleet with software updates, which seems like a strictly better solution in the long term. It seems like you're making perfect the enemy of "better".