The company's Google unit has conducted driverless vehicle testing for six years in Mountain View, California, where it is based, and expanded testing to Austin, Texas last summer. In February, Kirkland, Washington, which is home to significant wet weather, was added as a testing site.

Major automakers, and technology companies led by Google, are racing to develop and sell vehicles that can drive themselves, but they have complained that safety rules are impeding testing and ultimate deployment of such vehicles.

Most of Google's 1.5 million miles of autonomous vehicle testing has taken place in California. But it has publicly sparred with the state since December when California proposed rules requiring a steering wheel, brake pedals and a licensed driver in all robot test vehicles on the road.
"Arizona is known as a place where research and development is welcome, innovation can thrive, and companies can set up roots," said Jennifer Haroon, head of business operations for the Google Self-Driving Car project. "The Phoenix area has distinct desert conditions, which will help us better understand how our sensors and cars handle extreme temperatures and dust in the air."
Google said its test drivers recently began driving four Lexus RX450h SUVs around the Phoenix area to create a detailed map of streets, lane markers, traffic signals and curb heights.