They say "at a safety level substantially greater than that of a human driver". This is a low bar to meet - some human drivers are
really bad. I know I would much rather trust my life to one of the Google self-driving cars than some of the people I got in a car with in college, for example.
It's also the wrong bar to meet, because lawmakers are going to be much tougher on AIs than on human constituents. It's not enough to be better than a human, you have to be so much better than a human that it'd be irresponsible not to mandate self-driving cars.