Which of the following should not be used when radio traffic is busy?

When radio traffic is busy, it is vital to prioritize communications that are critical to safety and maritime operations. Routine requests for docking are typically considered non-emergency communications. They do not relate to immediate safety concerns or emergencies and can usually wait until the radio traffic decreases.

Emergency alerts, safety communications, and distress calls are all essential types of communication in maritime operations. Emergency alerts are crucial for notifying vessels and authorities of urgent situations, safety communications help ensure the well-being of all vessels and crew in proximity, and distress calls are lifesaving communications that require immediate attention. Therefore, utilizing these types of communications, even during busy radio traffic, is necessary to uphold safety standards in maritime navigation. Prioritizing communication types based on urgency and importance helps maintain a clear and effective radio channel.