Perhaps it straddles the line between 3 and 4. I don't see much of a distinction between the passenger taking over, and a first responder taking over. Would Waymo put cars on the road that don't have pedals and a steering wheel if it were cheaper to do so? I don't think they would. I think they want a backup in case the car has to be driven by a human.
Here's how you can tell so that you don't get confused as easily in future. Level 3 cars can require the occupant to drive the vehicle, "When the feature requests: You must drive the car". Waymo even offers service to people who cannot drive whether that's legally (they aren't licensed) or physically (blind people can use Waymo but can't drive a car). They are simply not required to take over driving.
What does it mean exactly? Because this can mean everything really. I mean you could guide decision making process by "now press break, now reverse and...", is it still driving?
