What does a vessel not under command display in terms of lights?

A vessel not under command is required to display two red lights in a vertical alignment during nighttime or periods of restricted visibility. This signals to other vessels that it is unable to maneuver as required by the navigation rules.

The choice of "red over red" effectively communicates the vessel’s status, allowing other mariners to recognize that the vessel is experiencing difficulties and may pose a hazard. Navigational safety relies on clear communication through visual signals, and displaying two red lights serves a critical function in preventing collisions by alerting nearby vessels of the situation.

This adherence to maritime signaling conventions ensures that the information conveyed is universally understood among seafarers, enhancing safety on the waterways.