Recognising vessels by their lights
- Power-driven under way: masthead light(s), red port and green starboard sidelights, and a white sternlight.
- Sailing vessel under way: sidelights and sternlight only, no masthead steaming light.
- At anchor: an all-round white light (a large vessel shows two, plus deck lights).
- Not under command: two all-round red lights in a vertical line.
- Restricted in ability to manoeuvre: red-white-red all-round lights vertically.
Judging and acting at night
Risk of collision is judged at night just as by day: take a compass bearing of an approaching light, and if it holds steady while the range closes, a collision is developing. The same steering-and-sailing rules apply — early, bold action, and an alteration to starboard in a crossing or head-on meeting. In restricted visibility the boat navigates by radar and by sound signals, there is no stand-on vessel, and a small yacht keeps well clear of shipping that may not have detected her.
TIP — Two sidelights end-on means head-on If you see both a red and a green sidelight together, more or less ahead, you are looking at a power-driven vessel end-on and it is a head-on situation — both alter to starboard. One colour means you are seeing her from the side.
WARNING — At night, act on the bearing not the guess Distances and closing speeds are deceptive in the dark. Trust the compass bearing: a steady bearing with a brightening or closing light is risk of collision, and it calls for early, obvious action.