A clear passage width of ____ inches minimum must be provided where an incline platform lift or stairway chairlift is installed on stairways serving Group R-3 occupancies.

The minimum clear passage width requirement of 20 inches is essential for the safe and effective operation of incline platform lifts or stairway chairlifts in Group R-3 occupancies, which typically include residential buildings like single-family homes or duplexes. Compliance with this width ensures adequate space for individuals using mobility devices or wheelchairs to access the lift or chairlift comfortably.

This clearance is particularly important in preventing obstructions that could impede movement and pose safety risks. It accommodates not only the lift itself but also allows room for users and passengers to maneuver without risk of getting stuck or encountering hazards in a potentially cramped stairway. Adhering to these standards contributes to accessibility and universal design principles, making spaces safer for all users, especially those with disabilities.

In contrast, the other provided measurements do not align with the established requirements needed to ensure sufficient passage through the installation area for users and the operation of the equipment.