Google has expanded its self-driving car project testing to the Phoenix, Arizona metro area. This will be the fourth city in the U.S. that will have the company's driverless cars on the road.

Reuters stated:

"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 began testing self-driving car prototypes near its home base in Mountain View, California several years ago. In mid-2015, it expanded to Austin, Texas and earlier in 2016 it began testing those cars on the roads of Kirkland, Washington.