The permit is relatively flexible. Waymo's autonomous machines are allowed to drive day or night on both regular and rural roads, in fog (rather important for the San Francisco Bay Area) and in light rain. They can also travel on highways at speeds up to 65MPH.

Waymo applied for its permit in April, mere days after the DMV cleared the way for completely driverless testing.

While Arizona beat California to the punch on these kinds of tests, it's still a major milestone. The state is home to more than a few companies developing self-driving technology, including ridesharing behemoths Lyft and Uber. There's a good possibility rivals will watch closely to see how Waymo fares, and might see this as an incentive to apply for their own permits if they haven't already submitted their paperwork.