For me, intermittent intervention is the worst of both worlds. I need to be fully tuned out, as on a plane, train, or bus, or as a passenger in a car someone else is driving. Or I need to be fully tuned in, fully engaged in driving the car. Passively observing while the car drives itself, supposedly ready to intervene the moment it deviates, pretty much guarantees my mind will be wandering and inattentive at the moment of truth.
With any luck I'll be dead, before continuously driving your own car finally goes out of fashion.