Regulators may question Tesla's belief that humans can reliably supervise self-driving software

When Joshua Brown switched on the Autopilot feature of his Tesla Model S on May 7, he would have been warned not to trust it. "Always keep your hands on the wheel. Be prepared to take over at any time," says the standard warning presented when Autopilot is turned on. But later that day Brown was killed when his car drove itself into the side of a semi-trailer that Autopilot had not detected. Federal investigations into the crash by the National Highway Traffic Safety Administration (NHTSA) and the National Transportation Safety Board (NTSB) may now question whether Tesla's design asks too much of drivers.