"The hard work is left to be done by the DMV," said Bryant Walker Smith, a fellow at Stanford's Center for Automotive Research.
Still, he points to a statistical basis for safety that the DMV might consider as it begins to develop standards.
After crunching data on crashes by human drivers, Walker Smith noted in a blog post earlier this year: "Google's cars would need to drive themselves (by themselves) more than 725,000 representative miles without incident for us to say with 99 percent confidence that they crash less frequently than conventional cars. If we look only at fatal crashes, this minimum skyrockets to 300 million miles. To my knowledge, Google has yet to reach these milestones."