On a recent weekday test drive, the safety drivers were still an essential part of the experience, as Uber’s autonomous car briefly turned un-autonomous, while crossing the Allegheny River. A chime sounded, a signal to the driver to take the wheel. A second ding a few seconds later indicated that the car was back under computer control. “Bridges are really hard,” Krikorian says. “And there are like 500 bridges in Pittsburgh