On the highway on-ramp you engage auto pilot. When you are 5,2, and 1/4 mile away from the off ramp you get a warning that auto pilot is preparing to disengage.
If you do not accept and manually turn off auto-pilot, it slows down safely to a stop in the break-down lane.
That's exactly how Volvo's Drive Me project is supposed to work.
http://www.volvocars.com/intl/about/our-innovation-brands/in...
That sounds about right. The ability to read/write/etc. while driving on the highway would actually be a huge win for a lot of people. And, equally important, it seems achievable in, perhaps, a single digit number of years.
But there would need to be an unambiguous mode change from "you can do Facebook now" to "you're driving" with plenty of time to make that shift.
This isn't as sexy as roboUber, shared cars, etc. but I'm inclined to agree that getting the last 10% of the way to unsupervised self-driving in essentially all situations is going to take a very long time.