[IanCal]

It depends on where the 80% is. If it's "80% of the roads in the country" that's one thing, if it's "at random points, at any time and on average for 20% of your journey you'll be taking control" that's another.

It's all about predictability. Even just full motorway / major road driving would be pretty awesome, and the car would know when it's coming up to a section you need to drive and you can have plenty of warning. Not "HELP DRIVER I SAW EITHER A LEAF OR A CHILD QUICK TAKE OVER"