Re: However
"Humans cannot maintain a high level of concentration for long periods when not actually doing anything." - This exactly. If I was sitting there in the driver's seat not actually driving the car, my attention would wander fairly quickly. I agree that this job is impossible to do to an acceptable standard, and no-one can be expected to react appropriately quickly if circumstances dictate.The whole thing is unreasonable.
It is completely different if you are actually driving the vehicle.