What is the sound signal for all encumbered vessels in restricted visibility?

• A. One long, two short
• B. One long
• C. Three short
• D. Two long

Answer: (A)

In restricted visibility, vessels that are restricted in their ability to maneuver must make their status known to others with a specific whistle signal. The pattern one long blast followed by two short blasts, repeated as needed, cleanly communicates that the vessel cannot easily change course or speed to avoid a collision. This lets other vessels take early and safe action, such as reducing speed and keeping well clear.

Other patterns are used for different situations, so they don’t convey the encumbered maneuvering status as clearly. A single long blast, three short blasts, or two long blasts do not indicate restricted maneuverability in the same way, and could be misinterpreted.