And you don't even know until it is too late even if you are paying attention. Suppose you see the obstruction well in advance. You expect the car to change lan

And you don't even know until it is too late even if you are paying attention. Suppose you see the obstruction well in advance. You expect the car to change lanes. You get past the point where you would have changed lanes but there's still time. You aren't yet aware that the car is missing the obstruction. A moment later you are much closer and make the judgement that the car is making a mistake. You grab the wheel but now it's too late. The alternative is taking control of the car all the time. Something nobody is going to practically do.