Autonomous driving technology has come a long way in the past few years and Waymo has announced its self-driving vehicles are now being tested on public roads without anyone in the driver’s seat.

This is a big leap forward as most autonomous vehicles require a safety driver who can take control if something goes wrong. Waymo used to use safety drivers but the company says that after more than eight years of development, they are no longer needed.

The company will operate a “subset” of its fleet in the Phoenix metro region in fully autonomous mode. Over time, the company intends to expand its coverage area to a region that’s “larger than the size of Greater London.”

In order to go fully driverless, Waymo vehicles have driven more than 3.5 million miles autonomously since 2009 and the company has subjected its cars to more than 20,000 individual scenarios on its test track. Besides the real world experience, Waymo has been running simulations where its software drives more than 10 million miles every day.

Should something go wrong with one of its driverless vehicles, Waymo says there shouldn’t be any problems as they are equipped with backup steering, braking, computer, and power systems. The systems are designed to bring the vehicle to a safe stop in the event of an emergency.

Waymo will be inviting members of its early rider program to use the fully autonomous vehicles over the course of the next few months.

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