And this is why engineers have invented the dead man's switch a long time ago: https://en.wikipedia.org/wiki/Dead_man%27s_switch The basic idea is that the switch can only be maintained in a non-braking state by an alert, not-incapacitated person. If you press too hard, it brakes; if you don't press hard enough, it brakes. You have to apply just enough force, and that's something only an alert person can do. Clearly,…
Or conversely, suppose the switch must be maintained while the car is in autonomous mode, should the car pull over and stop on the side of the freeway? In terms of user experience I would expect the car to continue to the destination. The commenter discussing the use of sensors to detect the state of the driver and act accordingly makes more sense.