The cars don't have to be perfectly safe, just safer than the average driver.
Why are people looking at the extremes? Only human drivers or a completely self driven car? What about a driver assistance system, that corrects a Human's stupid mistakes and still lets the human drive. I'm sure this hybrid (which is the current industry) is safer than both your extremes
Are there statistics?
It's true that humans do stupid things, but so do robots.
What would be _safer_ is an automated "hit" avoid system (if you're about to hit a wall, warn!!) or long distance driving system (for trucks/buses).
I think (and I could be wrong) that there are many more cases where conservative driving is safer than aggressive driving.
In a lot of the cases mentioned, doing nothing or stopping are the safest choices. What's safe to drive over? Just assume everything is unsafe and only drive over it if it puts others in danger to avoid it.
If the road is blocked and you need to communicate to navigate, don't. Wait.
If the road conditions are changed due to construction in ways the car can't understand, stop. Find a new route.
Most humans wouldn't do these things. The nice thing about the autonomous car is that it can drive extremely cautiously.
