Trying to Win the Public’s Trust With Autonomous Cars, at 120 M.P.H.

Markus Hoffmann, an engineer at Audi, prepared himself for a high-speed run around the Sonoma Raceway here in Northern California.
But instead of grabbing the steering wheel, he clutched a button he would release only if something went awry. The car, which he called Robby, was going to negotiate the two-and-a-half-mile Nascar track by itself — at 120 miles an hour.
“If something goes wrong, I’ll take over,” he said, giving a thumbs-up to engineers in the stands.