Navigation lights: how to identify a boat at night

At night, prescribed navigation lights show coloured sectors and white lights to make a vessel’s direction and configuration visible. Learn to recognise the lights, keep a proper lookout and a safe speed, and do not rely on a single distant observation.

Coloured lights and sectors of visibility

The international regulations for preventing collisions at sea prescribe lights with colours and sectors of visibility that help show a vessel’s orientation. On a power-driven vessel under way, a red light is visible from the port side and a green light from the starboard side. The masthead light and sternlight, depending on the vessel’s configuration and size, complete its profile. Different requirements apply to some sailing vessels and in particular situations.

If you see only another vessel’s red light and sternlight, you may be looking at her port side as she moves away; the green light corresponds to her starboard side. Distance, reflections, shore lights and weather can make interpretation difficult, however. Do not assume that a missing light means the vessel is not there or that your route is clear.

Navigation lights provide useful information but do not replace keeping a proper lookout. Keep watching and listening, use the radio when required, and adjust speed and course to visibility. If you cannot work out the situation, reduce speed safely and be ready to avoid a collision without making a sudden manoeuvre that creates another danger.

• Red: the port-side sector; green: starboard, under the applicable rules.
• White lights and additional configurations depend on the vessel’s type, size and status.
• Shore lights, reflections and distance can make identification difficult.
• Keep a proper lookout and a safe speed: lights do not replace observation.

Check your own boat’s lights

Before going out at night, switch on the lights and check from different positions that they are visible, the correct colour and not screened by a canopy or equipment. Check the power supply and any required spare bulbs, and make sure everyone on board knows how to switch the lights on. The required configuration depends on the vessel’s type and length and on the circumstances: consult the international rules and the boat’s manual.

A failed light can make it difficult for others to identify your vessel and where it is going. If an essential light fails, avoid continuing in conditions that reduce visibility. Consider returning to port or finding a safe shelter, and repair the system before setting out again.

Quiz Patente Ufficiale can help you revise navigation lights, signs and maritime rules through study chapters, timed quizzes and a review of your most frequent mistakes.