For motor vessel underway greater than or equal to 50 meters, which lights are required?

• A. Stern light, and sidelights
• B. Masthead light and sidelights only
• C. Stern light, two masthead lights, and port and starboard side lights
• D. All-round white light

Answer: (C)

For a motor vessel underway and at least 50 meters long, the lights must clearly show both the vessel’s length and its direction. That means two white masthead lights arranged in a vertical line, a stern light, and the standard port and starboard sidelights. The upper masthead light is the forward one, the lower masthead light marks the aft end, so other vessels can gauge how far away and where the vessel is heading even at night or in poor visibility. The sidelights indicate left and right sides, helping others determine bearing and risk of collision, and the stern light shows from the rear.

So, having a stern light, two masthead lights, and the red/green sidelights satisfies the requirement. The other options omit one or more of these essential lights.