To limit the probability that, during a failure of the normal power supply, persons will be trapped in an elevator, which could lead to harm to persons.
To limit the probability that, during a failure of the normal power supply in an emergency situation, emergency generator power supplies to elevators will not be capable of performing their intended functions for a length of time sufficient for emergency responders to carry out their duties, or for persons to evacuate or move to a safe place, which could lead to the inability of elevator systems to be used in emergency response operations, which could lead to delays in emergency response operations, which could lead to delays in the evacuation or movement of persons to a safe place, which could lead to harm to persons, including emergency responders.