What action is a vessel required to undertake when approaching another vessel on a collision course?

When a vessel is approaching another vessel on a collision course, the correct action is to alter course or speed to avoid a collision. This is in accordance with the International Regulations for Preventing Collisions at Sea (COLREGs), specifically Rule 8, which emphasizes the importance of taking early and substantial action to avoid collisions.

Altering course or speed provides a clear initiative in avoiding the situation, which is essential for both vessels involved. It ensures that both vessels can see the other's intentions and act accordingly, thereby enhancing safety at sea. If a vessel were to maintain its current course and speed, it could lead to a collision, as it would not communicate an intention to change the scenario.

Taking a direct approach towards the other vessel in an attempt to assess intentions can create confusion and increase the risk of collision. Similarly, signaling the other vessel to change its course does not guarantee that the other vessel will receive or act upon the signal in time to prevent an accident. Therefore, proactively altering course or speed is the most responsible and safe action a vessel can take in these circumstances.