Of course, because however controlled is the environment it runs in, all sorts of unplanned things can happen. A tyre blowing out. A passenger pressing the emer

Of course, because however controlled is the environment it runs in, all sorts of unplanned things can happen. A tyre blowing out. A passenger pressing the emergency stop button. A person or animal entering the tracks after defeating the barriers. Flooding in a tunnel. All of these events need a fast response regardless of whether the hardware detects the problem and stops by itself or not, even if just to evacuate the people that are inside the stopped cars.