"Sometime next year," Elon Musk says, "you'll be able to have the car be autonomous without supervision."

"None of us have any idea when full self-driving will happen," counters Gill Pratt, a leading expert in robotics and director of the Toyota Research Institute.

Beyond Musk, who has said twice this year that Tesla could have a million "robotaxis" on the roads next year, few experts in autonomous cars believe that the technology is ready to safely chauffeur occupants in any and all driving conditions. And that's before the regulatory hurdles, including a quaint-seeming 1971 New York law that requires at