For passenger elevators with automatic leveling devices, door opening may begin within how many inches of the landing for drive systems that do not use static drives?

The correct answer is 18 inches because automatic leveling devices in passenger elevators are designed to ensure that the elevator stops close to the landing for safe and efficient unloading of passengers. For drive systems that do not utilize static drives, regulations typically specify that the door opening can begin within 18 inches of the landing. This measure allows the elevator to maintain proper safety standards while accommodating natural variations in landing positions due to mechanical tolerances or building settling.

Understanding this threshold is important as it is a key factor in ensuring that the elevator's operational safety features function correctly. By adhering to this standard, elevator design and operation minimize risks associated with gaps between the cab and landing. Therefore, the specification of 18 inches serves to balance accessibility with safety, ensuring a smooth transition for users as they enter or exit the elevator.