@Roy Kamisato:  You don't seem to understand that the way driverless technology is evolving, traffic for the most part will be a thing of the past and a very infrequent event which would make driverless cars significantly more efficient in transporting people from Point A to Point B.  The whole reason why there is traffic is due to human error.  Take that out of the equation and most traffic incidents will be stalled cars of which the traffic impact will be minimized because driverless cars will automatically drive around a stalled car in unison without having to slow down more than necessary.  A ride on the rail only taking half an hour is only true if the starting and ending commute points are within 250-500 yards of a rail station.  Not realistic for most people.  As for the article you linked, that's the opinion of one person with a pessimistic view of technology which is evolving fast and will eventually overcome the problems that he's talking about.  Just a matter of time.