Volvo, Mercedes, Audi, Tesla and others already have cars on the road with a bunch of autonomous features. That includes full stop-and-go radar cruise control, lane centering, parking assistance and more; in fact, with all of its stuff activated, our latest long-term Mercedes E400 wagon is probably controlling more inputs than the driver under normal circumstances. But none of that makes a car "autonomous." Tesla calls its system Autopilot, to its own peril; Audi's is called Traffic Jam Assist; and Volvo's is DrivePilot. All of them turn the wheel, at least on the expressway, slow for stopping traffic and accelerate when it has cleared.