You're assuming an AGI would have all the characteristics of a machine algorithm and enough intelligence to do exactly what a human would/should (or better) in all driving situations.
And yet there is no evidence that self-driving systems are any safer than human drivers, or that they'll ever even be as safe as human drivers, let alone safer than them.
What do you mean "no evidence"? The companies testing self-driving cars now have hundreds of millions of miles driven and I haven't seen any reliable report showing they have higher kill rates than human drivers.
It would seem entirely possible that large amounts of highway driving can be handled by self-driving cars with slightly lower rates of accidents (tired and drunk people kill a lot of people!)
Well we haven't invented AGI yet, and so we don't even know if it will be possible to control them with an objective function. So your opinion is entirely speculative and not based on any science.
You can't be serious. Human are notoriously bad in situations where nothing happens 99.9% of the time but requires quick reaction 0.1% of the time.