What are the requirements for the positioning of sidelights on a vessel?

The requirement for sidelights to be installed on both sides of the vessel is essential for ensuring that a vessel's presence and direction can be identified by other vessels approaching from either side. Sidelights are critical components of a vessel's navigation lights, specifically designed to indicate the port and starboard sides respectively. The placement of these lights allows for effective visual communication of a vessel's heading, which is crucial for the safety of navigation, particularly in crowded or narrow waters.

When a vessel is approaching, other mariners can determine its direction of travel based on the sidelights. If sidelights were only installed on one side, it would create ambiguity regarding the vessel's orientation and movement. The requirement to have sidelights on both sides enhances navigational safety and compliance with COLREGs (Convention on the International Regulations for Preventing Collisions at Sea).

While other options mention aspects that can contribute to the effectiveness of sidelights, they do not encompass the fundamental requirement for navigation safety provided by having these lights on both sides of the vessel.