Level 2+/3- (best described as “Hands-off, eyes-on, mind-on”): This is not an SAE automation level, but it approximates to a system with operational design domain (ODD) limits maintained via over-the-air updates and an advanced IR vision DMS to permanently monitor driver state. Level 2+/3- will be distinguishable from Level 2 by long duration lane centering for a “highway assist” function — à la Autopilot.
GM’s updated Super Cruise will meet the definition for Level 2+/3- in 2020 and you can expect similar systems to be launched by every OEM by 2023. Tesla’s Autopilot/Full self-driving will be classed as Level 2+/3- with the addition of an ODD and IR vision DMS.
In a Level 2+/3- system the human driver will be liable at all times — including when the highway assist function is operational. The legal position for the driver would therefore be: “You engage it, you are liable for it.”
This idea is gibberish. The eyes-on, mind-on standard does nothing. It doesn't matter how much you're paying attention if your car decides to drive into a median (or a pedestrian) at 65 MPH. There's no way to realize it's happening and react quickly enough. If your response is "well the cars will be good enough that they won't drive into the median" then there's no reason for the eyes-on, mind-on concept and there's no reason for the drivers to be individually liable if the car fails.