A towing vessel 30 meters in length is pushing barges ahead. How many white masthead lights is the vessel required to show at night?

• A. One
• B. Three
• C. Four
• D. Two

Answer: (D)

Having a towing vessel push ahead with barges changes the required night lights: you must display two white masthead lights in a vertical line. This configuration signals to other vessels that you are towing, and helps indicate your length and arrangement at night. The normal navigation lights (sidelights and stern light) are still shown, but the key distinction here is the towing status, which calls for a second masthead light. So two masthead lights are required. A single masthead light would not indicate towing, and three or four would exceed the prescribed arrangement for this setup.