2. You can't really be certain
3. It would be good to be able to collect data of driver faults without crashes. But how do we do it without giving insurance companies more reasons to hike prices?
However I just wanted to say that a good driver can still avoid crashes even if not 'at fault' by driving defensively.
A friend of mine is a bad driver (in my opinion) but has never had an at fault accident. They have however had plenty of not-at-fault accidents but we're probably somewhat to blame or could have avoided if being more careful.
1. Improved visibility: A human driver sits in the driver seat, and looks at the outside world from inside the car - partly through mirrors, partly with the view obscured. A self-driving car (at last current potential vehicles) has a view without being obstructed by the car's frame.
2. No limitation on focus: As a human driver, I can look to the front, or the back, or the sides, but I can't look everywhere all the time. I can do my best to maintain an overview of my surroundings, but need to update this constantly by changing where I'm looking - if I want to see if there's someone behind me, I (for a moment) have to stop looking where I'm going. Automated vehicles don't need to stop looking to the front to see to their back or the side. They can see a car 200 feet away coming from the right without having to miss the pedestrian coming from the left.
I'm not saying that self-proclaimed self-driving cars do this already, but looking at perception capabilities, self-driving cars have the potential to avoid more accidents than humans.