> machine must be at least good as the human would be in every situation or we're better off leaving humans in control with machines augmenting their abilities.

That isn't quite right. There can be situations where the human is better, so long as in the majority of situations the machine is better. This is why I said it is a statistical question. I'm not demanding perfection, I'm asking for better than humans overall. Of course if the machine knows it is in a situation where it isn't as good it is fine to make the human drive.