Google’s self-driving car business Waymo has begun testing cars on US public roads without a human at the wheel to take over.

The company has unleashed minivans on the streets of Phoenix, Arizona, with its employees in the rear seats but no one in the front.

While they can’t steer or control the car, they can hit an emergency stop button.

There are plans in place for members of the public to ride in the vehicles soon, and Waymo is advertising on its website for “early riders”.

Waymno said “within months” the autonomous vehicles will start carrying volunteer passengers, although it is likely they will have a back-up driver.