What must be assessed to determine an appropriate safe speed?

To determine an appropriate safe speed, it is essential to assess several factors that can impact navigation. The visibility and traffic density are critical elements in this evaluation. Visibility affects a vessel's ability to see other vessels, navigational hazards, and aids to navigation, while traffic density indicates how many other vessels are present in the area.

When visibility is low, for instance due to fog or heavy rain, it is prudent to reduce speed, allowing for better reaction time and safer navigation. Similarly, if the area is congested with other vessels, a lower speed may be warranted to avoid collisions and ensure that the vessel can maneuver safely if needed.

While other factors such as engine size, the number of nearby vessels, or weather forecasts can influence safe navigation, they do not provide as comprehensive an assessment of safe speed as visibility and traffic density do. These two aspects are aligned with the COLREGs’ guidance on maintaining a safe speed at sea.