Is a vessel less than 50m in length required to display two mast headlights?

A vessel that is less than 50 meters in length is not mandated to display two masthead lights. According to the COLREGs (International Regulations for Preventing Collisions at Sea), vessels of this size have specific requirements for displaying navigating lights, which typically include a single masthead light when underway. While smaller vessels can voluntarily display two masthead lights as a means to enhance visibility or for specific operational procedures, it is not a compulsory requirement.

This gives smaller vessels some leeway in how they manage their lighting based on their operational context or to improve their visibility without being required to do so under the regulations, which is why the correct answer reflects this understanding.