You should always operate at a slower speed at night and be on sharp lookout for the lights of other vessels. The lights displayed by other vessels will help you determine whether they are operating under power or sail, and their direction of travel. Once you determine this, you can apply the same navigation rules used in the daytime. Never assume that the lights of other vessels are working properly. Allow plenty of time and distance to give way if needed, even if the lights indicate you are the stand-on vessel.
Power Driven Vessels at Night
When you see a green and a white light, you are the stand-on vessel. You should remain alert, but you should be ready to give way.
When you see only a white light, you are overtaking another vessel or it is at anchor. It is the stand-on vessel, whether underway or anchored. You can go around it on either side.
When you see a red and a white light, you must give way to the other vessel. Slow down and allow the vessel to pass, or you may turn to the right and pass behind the other vessel.
When you see a red, a green, and a white light, you are approaching another power-driven vessel head-on and both vessels must give way.
Sailing Vessels at Night
When you see a red and a green light but no white light, you are approaching a sailing vessel head-on and you must give way.
When you see only a green light or only a red light, you may be approaching a sailing vessel and you must give way. A sailing vessel is always the stand-on vessel except when it is overtaking.
Towing Lights
When commercial vessels are towing or pushing a barge, they display one or more yellow lights in place of a sternlight. There may be an unlit space of several hundred yards between the lights displayed on the bow and stern of the composite formed by the commercial vessel and its bargeLearn to recognize commercial vessel lights if boating on rivers, harbors, or coastal waters.
