What signal do vessels underway in restricted visibility sound?

• A. One prolonged followed by two short blasts
• B. Two short
• C. Three long
• D. One prolonged

Answer: (A)

In restricted visibility, ships use whistle signals to broadcast their status so others can take appropriate action. When a vessel is underway but its ability to maneuver is restricted, the prescribed signal is one prolonged blast followed by two short blasts, and it should be repeated at intervals not longer than two minutes. This exact pattern flags to nearby vessels that the broadcasting ship cannot safely maneuver to avoid a collision, prompting others to reduce speed, proceed with caution, and keep well clear. The other patterns do not convey that RAM (restricted in maneuverability) condition, so they aren’t the correct signal for a vessel in restricted visibility that is maneuver-restricted.