When is a vessel operator required to reduce speed to the minimum at which the vessel can be kept on course?

A vessel operator is required to reduce speed to the minimum at which the vessel can be kept on course when navigating in conditions of restricted visibility, such as fog or heavy rain. This requirement is in accordance with the International Regulations for Preventing Collisions at Sea (COLREGs), specifically Rule 6, which emphasizes the need for safe navigation to prevent collisions. Additionally, operators must consider other factors such as the presence of other vessels, the depth of water, and the maneuverability of their own vessel.