@Filippo
Accidents rate are just numbers.
You are correct and the question is indeed a practical one. However, I don't want to be one of those numbers. It's not that I don't trust computers, it's that I don't trust the motor vehicle authorities with them.
As an example I would point out that in several Provinces in Canada, we have many deaths from collisions with wildlife on the road. Around here we see groups of deer along the highways. As you approach them, one or two will usually wait until you get right up to them, then they will panic, and run right in front of the car. No problem, a human sees a deer and slows down or stops until it is clear that none of them are going to run. Perhaps a computer can visually tell the difference between a deer or moose and people, but it will probably be difficult and the driverless car would logically not be applied to this area. In reality what is likely to happen is that we would get more auto related deaths in this area than in cities and that it would be averaged out. So, we end up with more deaths here and lots less in the cities. Such are the ways of bureaucracy where "accident rates are just numbers".
BTW: Just so you can visualize the reality of wildlife problems. Many deaths caused by deer are from people swerving to avoid hitting the animal. This does not work when there is a 200 foot drop beside you.