The only slight problem with that is that in order to react at all in time, you must be paying the same amount of attention as you would if there was no autonomous drive system at all. This is otherwise known as the human being in the loop. Removing the human from the loop in aircraft automation has been a source of unending problems, and only recently one could say that it's a reasonably well understood problem - if not quite solved just yet. Don't forget we're talking about trained professional pilots here.
So, when faced with a self-driving car, the relatively untrained non-professional driver will always be so far out of the loop, that there's no way for him to overtake control safely in real time.
If you read the article, in the instances where the automation didn't know what to do, it pulled over and stopped:
Construction work, however, proved trickier. When faced with a partially blocked-off road, the car switched between autonomous and manual modes and then braked to a halt, requiring Urmson, the safety driver, to take control.
The driver doesn't need to react in time - the car does that. The driver merely needs to make the next decision to start moving again and guide the car to where it needs to go.