So it would seem purely based on these numbers that the Google cars have had about 4.5 times the mean rate of property-damage-only crashes. However, these statistics don't show us what the shape of the curve looks like, so we have no idea what percentile the Google cars are in.
If we take Google at their word that not one of the 11 crashes was caused by the self-driving system, then these numbers aren't evidence against the self-driving car being safer even with human drivers sharing the road. It's possible the car was driving unsafely in some way that increased its risk of accident without ever directly causing them, but we can't even guess at that without knowing the probability of their crash rate being this distance from the mean by pure chance.
So, do you really think the roads will only be safer when all cars are self-driving--you don't believe there will either be an incremental benefit in overall safety as more self-driving cars get on the road, or a specific safety benefit to owners of self-driving cars?
If we take Google at their word that not one of the 11 crashes was caused by the self-driving system, then these numbers aren't evidence against the self-driving car being safer even with human drivers sharing the road. It's possible the car was driving unsafely in some way that increased its risk of accident without ever directly causing them, but we can't even guess at that without knowing the probability of their crash rate being this distance from the mean by pure chance.
So, do you really think the roads will only be safer when all cars are self-driving--you don't believe there will either be an incremental benefit in overall safety as more self-driving cars get on the road, or a specific safety benefit to owners of self-driving cars?