What is characterized as a "reciprocal or nearly reciprocal course"?

The term "reciprocal or nearly reciprocal course" refers to a situation where two vessels are approaching each other from opposite directions or nearly opposite directions. This condition is often characterized by the visual alignment of the masthead lights of the vessels, which appear to be in line with each other when viewed from either vessel.

When the masthead lights of both vessels are aligned, it indicates that they are on a course that is either directly reciprocal or very close to being reciprocal. This means that each vessel is facing the other and could potentially lead to a situation where they need to take actions to avoid a collision.

In contrast, parallel courses would not create a situation of risk for collision since the vessels are not moving directly towards each other. Similarly, vessels overtaking or one crossing ahead of another do not necessarily reflect a reciprocal course scenario, as these involve different navigation dynamics. Therefore, the alignment of mast headlights is the most indicative feature of a reciprocal or nearly reciprocal course.