My guess is that even if we have cars that are 90% autonomous (at least on highways) by 2015 and fully robotic in a half-dozen years as Elon Musk promises, it will take substantially longer than that to modify infrastructure to meet the demand. If no retrofitting is required, then that’s a whole different conversation. From Mike Ramsey at WSJ:

“Tesla Motors Inc. plans to unveil features that enable more computer-controlled driving of its Model S electric sedan on Thursday, following up on tweets sent by the company’s founder last week, according to a person familiar with the matter.

At an event scheduled for Thursday in Hawthorne, Calif., the Silicon Valley auto maker will announce the latest upgrades, about a week after Chief Executive Elon Musk posted a pair of tweets suggesting the auto maker soon would announce a product he referred to as ‘D.’

A Tesla spokeswoman declined to comment on the specifics of this week’s announcement.

Tesla’s foray into features that allow autonomous driving reflects a wider push among auto makers to produce cars that can handle more driving functions on their own. Mr. Musk recently said Tesla will have a fully autonomous car ready in five to six years.”