What happens if the person is driving at high speed when the signal comes to shut the car down? Does it only take effect when they park? Do they get a warning before parking that the car will shut down when they do?
The same thing that happens to an gas car your car would lose power and you would roll to a stop. This actually happened to me on my motorcycle I was going high speed on a windy road and just had passed 2 cars and moved in front of them and my engine died. It’s not fun but shutting the car off at any moment should be no different then any car breaking down.
It happens, I mean I've stupidly run out of fuel on the highway before. I think this is something that should be practiced at least once while taking driving lessons (like how you practice emergency braking and evasion on a motorbike)