If the car is not able to safely operate without constant human involvement then it definitionally requires a person on board.
If losing cellular service causes it to stop, then in emergencies you're pretty much guaranteeing a large number of roadblocks for emergency services, on top of their existing hazards to emergency services when operating in ideal environments.
> Should the car keep going when it is not confident to do so?
See above, re: if your car can't even pull over and park safely on its own it has no business being on the street.
If losing cellular service causes it to stop, then in emergencies you're pretty much guaranteeing a large number of roadblocks for emergency services, on top of their existing hazards to emergency services when operating in ideal environments.
> Should the car keep going when it is not confident to do so?
See above, re: if your car can't even pull over and park safely on its own it has no business being on the street.