It's a sunny morning at Sonoma Raceway, north of San Francisco—a great day for a race. My driver, Robby, pulls up to greet me. Robby is not a person. It's a car—an autonomous racecar, to be precise—and it's ready for a fight. Outwardly, Robby is an Audi RS7 sport sedan, bright red and tarted up with black racing stripes and a giant logo. On the inside, however, it contains some of the most sophisticated autonomous-driving equipment—cameras, laser scanners, accelerometers, precision GPS receivers, microprocessors—on the planet.

As I stand there, helmet in hand, admiring the machine idling in the pit lane, Klaus Verweyen, head of Audi's piloted-driving development program, explains how the ride will go. First Robby will take me on a few hot laps around Sonoma's 2.5-mile circuit, home to many NASCAR and IndyCar races. Then I'll hop into a conventional—i.e., nonautonomous—model to try to beat that time. It's man versus machine, a John Henry-like battle for the postmodern age.

The ride is aggressive but clean, fast but not furious.

As I slide into the passenger seat, I'm greeted by a young engineer named Markus Hoffmann. He's been with the same Audi program for several years, but today his only job is to hold a kill switch that will instantly return Robby to human control if it tries anything suspicious. Besides that, he'll just enjoy the ride. I buckle up and tighten my chin strap. Then Hoffman pushes the button on the center console, and we take off down the front straight like a cannon shot. We scream through 60 mph, then 80, then 90. Turn One arrives quickly, and Robby grinds the brakes down to a perfect entry speed. The steering wheel snaps smartly to the left. At the apex, Robby throttles up and spins the wheel back in the opposite direction, carrying us smoothly out and onto the next turn.