What is the purpose of the “Not Under Command” indicator in COLREGs?

Prepare for the COLREGs Scenarios Test. Enhance your maritime navigation skills with interactive simulations, multiple choice questions, and detailed explanations. Ace the test with thorough practice!

The main idea here is understanding what Not Under Command signals. It is used to indicate a vessel that cannot maneuver as required by the collision regulations due to an exceptional situation, such as a loss of engines or steering. To make this clear to others, the vessel displays specific indicators: a day shape of two balls in a vertical line and, at night, two all-round red lights in a vertical line. This tells other ships that this vessel cannot safely alter its course or speed to avoid a collision, so they must take early and substantial action to keep well clear.

In practice, this signal helps the other vessel know that it cannot rely on the usual maneuvering expectations and must plan to avoid the Not Under Command vessel accordingly. It’s not about towing or being anchored or in distress; it’s specifically about an inability to maneuver as required by the rules.