Under the Rules, when is a stand-on vessel FIRST allowed to take action to avoid collision?

The stand-on vessel is first allowed to take action to avoid collision when the give-way vessel is not taking appropriate action to avoid collision. This principle is rooted in the navigation rules designed to promote safety and prevent maritime accidents.

The stand-on vessel is expected to maintain its course and speed as long as it is safe to do so, primarily to avoid confusing the give-way vessel. However, if it becomes apparent that the give-way vessel is not acting in a manner that would help prevent a collision, the stand-on vessel must take proactive measures. This could mean altering its course or speed to ensure safety and avoid an accident. This rule emphasizes the importance of situational awareness in maritime navigation, highlighting that the responsibility to avoid collisions is shared.

The other options do not accurately reflect the rules governing stand-on vessels. The presence of the give-way vessel onboard does not determine the stand-on vessel's actions. Convenience is not a valid rationale for taking action, as that could lead to unsafe navigation practices. Similarly, reduced visibility can complicate situations but does not dictate when a stand-on vessel has the right to initiate avoidance maneuvers—the key factor is the lack of appropriate action from the give-way vessel.