Technologists exude favorable vibes about their 'thing'. Being focused individuals, they understand the problem at hand and how to solve it. However, they tend to be farsighted on technology and myopic on business, social, and governmental progress.
John Zimmer is probably right on his technology timing. However, he has not considered the social and political impact of putting millions of livery people out of work. The people to whom I refer are not sheepish tech workers that respond almost lifelessly to RIFs.
Livery people are usually union people, and they will regard this sea change as a threat worse than terrorism. 'Scabs' who run picket lines are not treated kindly by strikers. Automated vehicles that replace truckers, cabbies, bus driver, and other livery personnel will be treated like 'Terminators' in an apocalyptical war. They will be sitting ducks, and I am sure that John has not figured that into their programming.
Beyond the loss of jobs, many people will resent the loss of control over their mobility. Always obeying the rules of the road has never been popular. Google cars, roaming the streets of Mountain View, follow all the rules and are constantly being passed or rear-ended. In spite of their obvious benefits, automated vehicles will draw the same ire as stubborn mules or today's faltering automobiles that need repair but do not get it. People are shameless bigots when it comes to automation, and automated vehicles will bring this hatred into the open. Lots of cars will get the gas kicked out of them.
Lastly, automated cars will get pwned in a huge way. It will be worse than the little old lady who gets conned in a traffic accident scam. I know, automated vehicles will have lots of cameras and 'black boxes'. However, those will be easily circumvented by professional fraud artists. That raises the issue of who is responsible for an accident, a battle that could rage in the courts for a decade.
Automated transporation will happen, and the technology is moving forward to meet all the challenges of driving. However, the critical path will not be technological; it will be human will.