Unless you think Bob was causing accidents every thousand miles, I don't see how Google cars are "several orders of magnitude" better. Leaving aside the good-weather/known-roads aspect, of course.
The average accident rate in the US is something like one per 250,000 miles driven. (The average driver drives 15,000 miles per year, and goes about 18 years between accidents.)
So indeed, we can't draw much conclusion about the safety of Google's car relative to the average driver yet, except to say that it's not catastrophically worse.
So indeed, we can't draw much conclusion about the safety of Google's car relative to the average driver yet, except to say that it's not catastrophically worse.