How is the risk of collision determined at sea?

The risk of collision at sea is primarily determined when two vessels are approaching each other. As they get closer, the likelihood of a collision increases, which necessitates vigilance and action to avoid it. The dynamics of relative motion are critical here; as vessels approach, navigational decisions must be made based on their bearing and speed. This interaction becomes vital in managing the risk of collision, as the International Regulations for Preventing Collisions at Sea (COLREGs) establish guidelines for how vessels should behave in these scenarios to minimize risk.

The focus on relative motion highlights that other factors, such as distance or size of the vessels, are less critical on their own without considering the direction and speed of approach. For example, two large vessels may have a lower risk of collision if they are moving at significant distances apart or on parallel courses. Additionally, two vessels being stationary does not present a risk of collision since there is no movement to generate a collision scenario. Thus, understanding vessel movement and the conditions under which they are approaching each other is the most significant factor in assessing collision risk at sea.