Google's self-driving cars to face their toughest test yet

The move to Phoenix is the second new area for Google this year. In February, it began testing in Kirkland, Washington, which is significantly wetter than previous locations. Those previous locations were in California and Texas, though, so that's not saying much -- Kirkland is still dryer than the US average for inches of rainfall per year. It's suggested that, in addition to providing a new set of environmental challenges for self-driving cars, Arizona is potentially more open to the testing than California. Google's home state recently proposed new rules that would require a wheel, pedals and a driver to be in self-driving cars -- all things that are not present in Google's current prototype.