The thing is, most of the deaths from self driving will be seen as preventable, if only a human was driving. That's going to make it look bad, even if the numbers are less.

If you want to reduce deaths, I think you really want to invest in things like automatic emergency braking, monitoring driver attention, and safely stopping the vehicle if the driver is incapacitated. Having the computer supervise the human means the human is engaged in driving and aware of the circumstances for the most part; a computer supervising a human can act with great speed if the situation warrants, but a human supervising a computer is likely not to react so quickly.

Calculating just deaths / DrivingDistance is easy but overly simplifies the complicated comparison between human- vs self-driving. Comparing normalized deaths is not sufficient to persuade real people to choose self-driving over human-driving. Real humans and society take into account many more factors to accurately compare the two driving modes.

Take a hypothetical scenario where self-driving cars reduce deaths by 10x compared to now, but the deaths caused by self-driving cars are all small children and people with darker skin in human-preventable ways (you can imagine if cameras are used why this could happen). I doubt society would accept this tradeoff.

The safer future is to have humans still drive, but be enhanced by computers and cameras that are installed in the car.

Truth is, we will never accept robots on the roads that are as deadly as human drivers. Especially since they will fail in specific, surprising and hard to comprehend ways, see here.

Robotic drivers will probably need to demonstrate at least an order of magnitude improvement in safety before they can be accepted by the public.