Under which condition must a vessel take avoiding action as per Rule 19d?

The requirement for a vessel to take avoiding action, as per Rule 19d, specifically arises in situations where a close-quarters situation is developing and the vessel detects another vessel using radar alone. This scenario emphasizes the importance of radar as a navigational tool in reducing the risk of collision, particularly in conditions where visual detection may be compromised, such as poor visibility due to darkness or weather conditions.

When radar indicates the proximity of another vessel and an imminent risk of collision is identified, it is crucial for the vessel to take timely and appropriate action to mitigate that risk. The rule stipulates that both radar and visual navigation play significant roles, but in circumstances where radar is the sole means of detection, the operator must remain vigilant and proactive in ensuring safe navigation.

Other conditions described may not trigger an immediate requirement for avoiding action under Rule 19d:

• Visual detection can sometimes allow for different navigational decisions compared to radar detection, particularly if there is ample time to maneuver.

• An overtaking situation may not automatically necessitate avoiding action unless it escalates into a close-quarters scenario, which is not defined strictly by the act of overtaking alone.

• Relying solely on signals from other vessels does not cover the immediate need to act when radar