Approach lock under control is indicated by which signal?

• A. Flashing amber
• B. Flashing amber and green lock
• C. Solid green lock
• D. Flashing red

Answer: (A)

The signal pattern uses color and flashing to convey status while approaching a lock. A single flashing amber signal means you’re being guided through the approach under the lock operator’s control—proceed with caution and follow any directions given. The amber color signals caution, and the flashing pattern indicates active management of the approach rather than a free, uncontrolled passage.

Other patterns imply different conditions: a solid green lock generally signals a clearer or more immediate proceed status, a flashing red warns of danger or a stop, and a combined amber with green would indicate a different, specific status. But for approaching a lock under supervision, the flashing amber is the pattern you’d follow.