Arizona basically threw their citizens to the wolves with a 2015 self-driving car law that allowed anything and everything to go (you wouldn't even have to register your cars as self-driving for a period). This attracted tons of firms to test their cars in a lax regulatory environment but since the famous Uber death and a number of self-driving accidents, they have tightened the rules somewhat. I suspect they're still looser than average and there's some inertia from everyone setting up shop there originally.

From the original press release:

> "Part of what makes Arizona an ideal place for Uber and other companies to test autonomous vehicle technology is that there are no special permits or licensing required," the ADOT release said. "In Arizona, autonomous vehicles have the same registration requirements as any other vehicle, and nothing in state law prevents testing autonomous vehicles."

Article with latest updates: https://www.phoenixnewtimes.com/news/maricopa-county-sheriff...