The automated system can control the vehicle in all but a few environments such as severe weather. The driver must enable the automated system only when it is safe to do so. When enabled, driver attention is not required.
How bad will the roads be when we have thousands of people all very unsure of their driving skills driving in conditions that are dangerous to begin with? Seems quite the interesting issue.
The advent of cruise control has not made people incapable of using the accelerator. You occasionally meet 16-year-olds who enable it on any 35, 45 or 55 mph road when they reach the speed limit, because holding constant speed is a skill. But it's not difficult to refrain from using it for a while to brush up on the skill.
But I have done far more miles on highways in good conditions where an L4 system would be helpful. The tech is still useful even if it's not a complete solution.
People will still be wildly overconfident of their driving abilities.
People need to stop saying this. It doesn't matter if Level 4 specifies this, and someone claims a certain car successfully passes the test. No car in AI infancy is going to be 100%. Drivers must absolutely be prepared to take over in under half a second at all times. That's not likely to change for 30-50 years.
I found it quite socially irresponsible for him to mention during the keynote that it would be fine for his 80+ year old mother to continue driving when she becomes no longer capable of managing the vehicle on her own. It might be perfectly fine in a few decades. Not by 2020 though.