The signal One long, two short is used by which vessels in restricted visibility?

• A. All encumbered vessels
• B. Non-encumbered vessels
• C. Vessels not under command
• D. Sailing vessels only

Answer: (A)

In restricted visibility, sound signals tell other vessels about your ability to maneuver. One long blast followed by two short blasts is the warning signal used by vessels that are encumbered—meaning they’re not able to maneuver as freely as a fully capable vessel. This includes vessels not under command, or restricted in their ability to maneuver, or otherwise limited in how they can steer or stop. The idea is to alert other vessels to slow down or take early action to avoid risk, since the encumbered vessel may not respond quickly or as expected.

So, the best answer is that this signal is used by all encumbered vessels. It’s not for vessels that can maneuver normally, and it isn’t restricted to sailing vessels alone.