Must stop within 50 mm if arms are unlocked.

• A. Platform Movement Control
• B. Emergency Personnel Access
• C. Hydraulic Driving Machines
• D. Floor Area Limit

Answer: (A)

Platform movement control is the system that governs how the escalator or moving walk starts, runs, and stops. When the guard arms or safety interlock is released or unlocked, signals feed into this control so the platform is brought to a stop quickly and safely. The requirement that it must stop within 50 mm ensures that the platform ceases nearly immediately after the condition is triggered, minimizing the distance the moving surface travels and reducing the risk of injury or contact with moving parts. This is the specific function tied to stopping promptly under safety-interlock conditions. The other options describe different systems (emergency access, drive machinery, or floor area limits) that don’t control the immediate stopping behavior when an arm or safety interlock is unlocked.