What does Rule 19 concern?

Rule 19 of the COLREGs specifically addresses the conduct of vessels in restricted visibility, which refers to conditions where visibility is significantly impaired due to factors like fog, rain, or other obstructions. In such scenarios, vessels must take necessary precautions to avoid collisions, including navigating at safe speeds, maintaining a proper lookout, and using sound signals to communicate their presence and intentions to other nearby vessels.

The emphasis on restricted visibility is crucial because it greatly increases the risk of collisions, as vessels may not be able to see each other in time to take evasive action. Thus, Rule 19 elaborates on the appropriate navigational behavior and responsibilities of mariners under these conditions, ensuring that they remain vigilant and proactive in avoiding accidents.