This whole idea of automation isn't a very futuristic notion. Automation has fascinated the world time and time again, from the first time Ford introduced the production line (not exactly fully automated but a marked improvement from before) to the world of motion sensors and automated soap dispensers in your toilet. It isn't a new idea, but its an idea that confounds many because of its complexity to achieve the ultimate "Automated Car." Of course this project is far from finished but what we have here is quite amazing. Not only will it make 'driving' more relaxing, Google researchers say that road capacity can be increased but 100% because robots have better sense of estimation than human beings which will allow cars to be driven at closer distances from each other, and they can never fall asleep at the wheel which in turn may make roads safer.
Safer roads? Trains can now be fully automated, but cars? I don't think I'd be very comfortable with that.. Its just like flying in a plane without a human pilot, you know the plane has an Autopilot function but you wouldn't want it to be the one and only form of technology that separates your life and death. You'd like some form of backup. And in cars, I think humans should still remain as the primary source intelligence in cars, not some computer chip. And if you wanted to travel from your home to work, relaxed and unperturbed, there's already an invention that has been around since Gottlieb Daimler invented it in 1897; its called a taxi.
But if you'd like to know how all this gadgetry works, here's a graphical representation from Google which was published in the New York Times: