It was on the motorway near Phoenix, Arizona, that I realised fully driverless cars might be quite a distant dream. And that was because our Google Waymo robo-taxi seemed incapable of leaving that motorway. We were in Arizona to record a radio documentary for the BBC World Service about the progress towards creating autonomous vehicles that would make our roads safer and replace human drivers with robots. Google leads this race at the moment and for the past six months has been offering a robo-taxi service, Waymo One, to a select few early adopters in and around the Phoenix suburb of Chandler. Our first ride with Waymo took us through the quiet suburban streets, where traffic is sparse and drivers well mannered.

Nearly eight months after one of its autonomous test vehicles hit and killed an Arizona pedestrian, Uber wants to resume testing on public roads. The company has filed an application with the Pennsylvania Department of Transportation to test in Pittsburgh, and it has issued a lengthy safety report pledging to put two human backup drivers in each vehicle and take a raft of other precautions to make the vehicles safe. Company officials acknowledge they have a long way to go to regain public trust after the March 18 crash in Tempe, Arizona, that killed Elaine Herzberg, 49, as she crossed a darkened road outside the lines of a crosswalk. Nearly eight months after one of its autonomous test vehicles hit and killed an Arizona pedestrian, Uber wants to resume testing on public roads. Police said Uber's backup driver in the autonomous Volvo SUV was streaming the television show'The Voice' on her phone and looking downward before crash. The National Transportation Safety Board said the autonomous driving system on the Volvo spotted Herzberg about six seconds before hitting her, but did not stop because the system used to automatically apply brakes in potentially dangerous situations had been disabled.