Let's say you're willing to live with a
hundred million miles between a
significant mishap. And maybe that's
based on real-life driver data, and you
want to be at least as good as a driver.
In order to prove that you're at a
hundred million miles between mishaps,
you have to drive 300 million miles
without seeing any mishap. Or alternately
if you do see one, you have to drive even
further to make sure that it was just
normal statistical fluctuation and that
you don't have an unsafe vehicle. So
that's a whole lot of miles to do for
testing
 
