How many masthead lights should vessels of 50 meters or more display?

For vessels that are 50 meters or more in length, the correct requirement is to display two masthead lights. According to international regulations (COLREGs), vessels of this size must show two masthead lights to improve their visibility to other vessels, particularly in low-light conditions.

The purpose of having two masthead lights is to provide clear indication to other mariners about the size and heading of the vessel. The lights are positioned vertically, with the upper light generally set at a higher elevation, which aids in distinguishing larger vessels from smaller ones. This is especially crucial in busy shipping lanes or areas with other vessels, as it helps to enhance navigational safety and prevent collisions.

Additionally, smaller vessels have different lighting requirements, usually only needing one masthead light. This is why the number of lights corresponds to the vessel's size, with larger vessels needing more lights to convey their presence adequately and ensure that their maneuvering capabilities are understood by other captains and crews.