What is the primary focus of rules 4-10 in the COLREGs?

The primary focus of rules 4-10 in the COLREGs is to govern the conduct of vessels in any condition of visibility. This means that these rules are designed to ensure safe navigation and adherence to protocols regardless of whether visibility is good or poor.

Rules 4 through 10 cover a range of scenarios that vessels might encounter, including the responsibilities and actions that should be taken in various situations such as approaching one another, navigating in restricted visibility, and determining safe speed. The emphasis on "any condition of visibility" highlights the importance of situational awareness and proper conduct to prevent collisions at all times, as visibility can vary dramatically due to weather conditions, time of day, or environmental factors.

While the conduct of vessels in sight of one another and in restricted visibility is also covered by these rules, they are subsets of the broader spectrum of situations addressed by the rules as a whole. Thus, the accurate understanding of the overarching aim of these rules supports greater safety at sea.