What is the minimum visibility of a sidelight on a vessel of 20m in length?

For a vessel that is 20 meters in length, the minimum visibility for its sidelights is indeed 2 nautical miles. This requirement is outlined in the International Regulations for Preventing Collisions at Sea (COLREGs).

The sidelights, which are the green light on the starboard side and the red light on the port side, are crucial for identifying the orientation and movement of the vessel when at night or in reduced visibility conditions. The distance at which these lights must be visible is determined by the length of the vessel. For vessels that are 20 meters or longer, the COLREGs stipulate that sidelights must be visible from a distance of at least 2 nautical miles.

This visibility standard allows other vessels to detect and interpret the navigation status of the 20-meter vessel, helping to prevent collisions at sea. Knowing this heightens the awareness of maritime safety and ensures compliance with standardized visual signaling during nighttime navigation or adverse weather conditions.