Racing toward autonomous future, Cadillac and Mercedes-Benz reveal sultry, drive-it-yourself concept cars

In the autonomous-vehicle future, will the ultimate luxury become driving for yourself?

That appears to be the suggestion from General Motors' Cadillac premium-car unit and Germany's Mercedes-Benz-both unveiled lusciously-proportioned concept cars at August's Monterey Car Week, where executives for both companies took pains to say the vehicles would be best enjoyed if, well, you actually drove them.