Which signal indicates stand clear and do not enter during standard locking procedures?

• A. Flashing amber (approach lock under control)
• B. Flashing red (stand clear do not enter)
• C. Flashing Green (enter lock)
• D. Flashing amber and green (enter lock with caution)

Answer: (B)

Signals control access to a lock by indicating whether you should approach, stand clear, or enter. A flashing red signal tells you to stand clear and do not enter. Red is the stop cue—entry is prohibited because the lock may be in motion, not ready, or another vessel is inside. This safety safeguard prevents trapping personnel or equipment and avoids collisions. By contrast, flashing amber means approach under control, flashing green means you may enter, and flashing amber and green means enter with caution. So the flashing red signal is the one that communicates stand clear and do not enter.