I’m following the evolution of the self-driving technologies with a lot of interest. Many automotive companies say that by 2020/2022 they will commercialize autonomous cars that will reach the level 4 or 5 of the SAE International Automated Driving standards.
Below the table that is commonly adopted by all the automotive industry.
Wired points the level 3 human problem in a very clear way: humans are not capable to maintain their attention if they are not interested or required to. For simplifying, a crash in self-driving mode cannot be avoided thanks to the intervention of the driver that in the meanwhile could be reading a newspaper or watching a video. Humans are just too slow and in that case even too distracted for recognizing the risk and avoiding a crush.