When two power-driven vessels are crossing and at risk of collision, what action should the stand-on vessel take?

In the scenario where two power-driven vessels are crossing paths and at risk of collision, the role of the stand-on vessel is defined by the International Regulations for Preventing Collisions at Sea (COLREGs). The stand-on vessel is required to maintain her course and speed, thereby asserting her right of way. However, if it becomes evident that a collision is inevitable and action must be taken, the stand-on vessel is advised to take actions that are safe and effective for avoiding a collision.

Choosing to avoid a change in course to port when taking action is correct because it minimizes the risk of confusion or an unpredictable situation. In many cases, changing course to port can lead to potential collisions within the crossing situation, as the give-way vessel generally turns to starboard when it is necessary to avoid a collision. Therefore, to align with the most effective and safest practices, the stand-on vessel is recommended to avoid making a port turn if she decides to take evasive action.

The reasoning aligns with general navigation practices as well as the principles set out in the COLREGs, emphasizing predictability and clear intentions to reduce the risk of misunderstandings between vessels in a potentially dangerous situation.