Retractable arms must be locked and monitored.

• A. Mechanical Locking
• B. Non-boarding Arm Lock
• C. Traction Sheaves
• D. Power Transfer

Answer: (A)

Retractable arms must be held securely in place and continuously checked for proper operation to protect riders during boarding and alighting. The best way to ensure this is a mechanical locking system that physically secures the arm in the deployed position and prevents movement unless released by the control system. The monitoring aspect means sensors verify the lock is engaged at all times; if the lock is not engaged or a fault is detected, the escalator stops to prevent harm. Traction sheaves and power transfer are part of driving the escalator, not of securing or monitoring the retractable arms. A non-boarding arm lock relates to a specific safety purpose, but it doesn’t describe the general requirement to lock and monitor retractable arms during operation.