Most of what I've read about Google's car crashes is that it was the other driver's fault in just about all of them. Not saying I like Google, or that I'd trust them (software can be hacked, no thanks), just that the Google car was found not to be at fault in most of the crashes to date.
IIRC, the perfection of a computer driven car makes its actions difficult to anticipate for real drivers, and that was the explanation for the crashes.