Under which conditions is it advisable for a vessel to reduce its speed?

Reducing speed is crucial in specific conditions to ensure the safety of both the vessel and its crew. In situations of restricted visibility, such as fog or heavy precipitation, reducing speed helps the operator respond more effectively to unexpected obstacles or other vessels that may not be visible until very close. Heavy traffic also necessitates reduced speed to allow for the safe navigation around other vessels, providing more time to react to the movements of others. Additionally, when maneuvering near hazards, such as reefs, shallow water, or physical barriers, slower speeds afford the captain greater control and the ability to make precise adjustments, mitigating the risks of grounding or collisions.

While calm weather and open waters might allow for higher speeds, navigating in rough seas or approaching a coastal port can still warrant reduced speed depending on other factors like conditions or cross-traffic, but the most critical moments for speed reduction generally arise during restricted visibility, heavy traffic, or near hazards.