The first truly autonomous cars — vehicles that cruise the public streets with no one sitting behind the wheel to take over in case of emergency — have finally arrived. Waymo, which began life as Google’s self-driving car project, disclosed on Tuesday that it had let its driverless cars loose in parts of Phoenix, Arizona, with nobody in the front seats. Members of the public taking part in a Waymo trial in the desert city in the US south-west will be able to summon the vehicles through a ride-hailing app “in the next few months”, the company said. Potentially one of the most disruptive new technologies, as well as one of the most hyped, driverless cars have been at the centre of a race between big automakers and technology companies in the US, China and Europe. But while a number of groups are testing the technology on the streets with back-up drivers behind the wheel, most believe the advent of full autonomy is at least two years away. John Krafcik, head of Waymo, announced the milestone at a tech conference in Lisbon on Tuesday. Company employees have been climbing into the backs of its cars, choosing between three different routes, and letting the vehicle do the rest. The test, while limited to an unspecified area, is “not a one-time ride or a demo” but the start of “a new phase for Waymo and the history of this technology”, according to Mr Krafcik. The company planned to expand it to the entire 600 sq m Phoenix region, he added, without giving a specific timeframe.