This article is full of details and well worth a read. It's kind of a bummer for me, because I can't wait for the day when driverless cars replace the clueless drivers of Minnesota among whom I have to commute. But the technical challenges of bringing driverless cars into routine consumer use are still immense.

The article notes, about an expected transitional phase of development when driverless cars augment rather than replace human driving, "An important challenge with a system that drives all by itself, but only some of the time, is that it must be able to predict when it may be about to fail, to give the driver enough time to take over. This ability is limited by the range of a car’s sensors and by the inherent difficulty of predicting the outcome of a complex situation. 'Maybe the driver is completely distracted,' Werner Huber said. 'He takes five, six, seven seconds to come back to the driving task—that means the car has to know [in advance] when its limitation is reached. The challenge is very big.'"

My dream is the dream of fully door-to-door driverless cars. I think the article "Why Driverless Cars Are Inevitable--and a Good Thing"

http://online.wsj.com/news/articles/SB1000087239639044352490...

by Dan Neil of the Wall Street Journal, published last year, is a good commentary on why ordinary people will mostly be glad to use driverless cars, and regulators and insurers will be glad to nudge drivers to use them. But that's only if they work, and it's not clear how soon driverless cars will work reliably and be manufactured inexpensively enough to become routine on our streets and roads.