Waymo is already using autonomous vehicles in AZ without a safety driver behind the wheel. There are fully autonomous Waymo vehicles driving around in parts of AZ.
Which is why I am only a little bit surprised Uber beat Waymo to killing a pedestrian. Waymo is way too arrogant about it's capabilities, moving way faster than is reasonable or safe, and they use misleading statistics to insinuate their system is more capable than it is.
Note that they already know their cars will need help driving still, which is why they've assembled a call center for remote drivers to take over their cars in Arizona. Of course, those remote drivers likely can't intervene at nearly the speed of an onboard safety driver.