Locks retractable ramp until arm is secured.

• A. Floor Area Limit
• B. Non-boarding Arm Lock
• C. Traction Sheaves
• D. Pitch Diameter

Answer: (B)

The locking mechanism tied to the boarding arm is about safety interlock for the retractable ramp. When the ramp is extended or in a position ready for use, it must be secured by the boarding arm. The Non-boarding Arm Lock ensures that the retractable ramp stays locked until that arm is actually secured in place. This guarantees the ramp cannot move or retract while the arm isn’t latched, preventing misalignment, entrapment, or instability for riders or maintenance personnel. The other options don’t control this interlock: one relates to overall floor clearance, another to the drive traction components, and another to pulley size—none of which lock the ramp based on the arm’s secured status.