COLREGs for sailors: rules of the road, lights, shapes and a test
The International Regulations for Preventing Collisions at Sea (COLREGs, 1972) in plain words: who gives way to whom, what lights and shapes mean, and which sound signals to use — with drawings.
- Two sailing vessels: the one on port tack keeps clear of the one on starboard tack; on the same tack, the windward one keeps clear (Rule 12).
- An overtaking vessel always keeps clear (Rule 13). Two power-driven vessels head-on both turn to starboard (Rule 14); crossing, the one that has the other on her starboard side gives way (Rule 15).
- Priority (Rule 18): not under command or restricted in her ability to manoeuvre → constrained by her draught → fishing → sailing → power-driven.
- A sailing yacht under engine is a power-driven vessel — even with her sails up.
Who gives way
| Situation | Who keeps clear | Rule |
|---|---|---|
| Two sailing vessels, wind on different sides | The one with the wind on her port side (port tack) | 12(a)(i) |
| Two sailing vessels, wind on the same side | The windward one | 12(a)(ii) |
| You are on port tack, see a sailing vessel to windward and cannot tell which tack she is on | You | 12(a)(iii) |
| One vessel overtaking another | The overtaking vessel, sail or power | 13 |
| Two power-driven vessels meeting head-on | Both — each alters course to starboard | 14 |
| Two power-driven vessels crossing | The one that has the other on her own starboard side | 15 |
| A power-driven vessel and a sailing vessel | The power-driven vessel — unless she is being overtaken, or Rules 9 and 10 apply | 18(a) |
| A sailing vessel and a vessel fishing, not under command or restricted in her ability to manoeuvre | The sailing vessel | 18(b) |
| Narrow channels and traffic lanes | Vessels under 20 m and sailing vessels must not impede a vessel that can navigate safely only within the channel or lane | 9, 10 |
The windward side is the side opposite to the one on which the mainsail is carried. “Overtaking” means coming up from more than 22.5° abaft the other vessel's beam — at night you would see only her sternlight.
The order of priority
Rule 18 sets who keeps out of whose way, from the vessel that can manoeuvre least to the one that can manoeuvre best:
- Not under command — a breakdown means she cannot keep out of the way — and restricted in her ability to manoeuvre — dredging, laying cable, diving operations, some towing. Everyone keeps out of their way; the rule does not rank the two.
- Constrained by her draught — a deep ship that cannot leave the channel: other vessels, apart from the two above, avoid impeding her.
- Engaged in fishing — with nets, lines or trawls that restrict her manoeuvrability (not a boat trolling a line).
- Sailing vessel — under sail only.
- Power-driven vessel — including a sailing yacht under engine.
Two exceptions come first: whoever overtakes keeps clear (Rule 13), and in narrow channels and traffic separation schemes small craft and sailing vessels must not impede the ships that depend on them (Rules 9 and 10).
Give-way and stand-on: what each must do
- Is there a risk of collision? Take a compass bearing of the other vessel several times. If the bearing does not change appreciably while she comes closer, you are on a collision course (Rule 7).
- Give-way vessel: act early and substantially, so the other vessel sees it — one large alteration rather than several small ones; avoid crossing ahead of her (Rules 8, 15, 16).
- Stand-on vessel: keep your course and speed. You may act as soon as it is clear the give-way vessel is not doing so, and you must act when a collision can no longer be avoided by her alone. If you are under power in a crossing situation, do not turn to port for a vessel on your own port side (Rule 17).
- Always: keep a proper lookout by sight and hearing (Rule 5) and go at a safe speed for the visibility and traffic (Rule 6).
Navigation lights at night
| Light | Colour and arc | Where it shines |
|---|---|---|
| Masthead light | White, 225° | Ahead and to 22.5° abaft the beam on each side |
| Sidelights | Red to port, green to starboard, 112.5° each | Ahead to 22.5° abaft the beam on its own side |
| Sternlight | White, 135° | Astern |
| Towing light | Yellow, 135° | Astern, above the sternlight |
| All-round light | Any colour, 360° | All round the horizon |
What you see tells you the type of vessel, her size, what she is doing and which way she is heading:
Day shapes
By day, black shapes hoisted where they can best be seen say the same as the special lights at night:
Lights and shapes of a sailing yacht
- Under sail: sidelights and a sternlight. A yacht under 20 m may combine them in one tricolour lantern at the masthead (Rule 25).
- Under engine, with or without sails: the lights of a power-driven vessel — a white masthead light, sidelights and sternlight. Never the tricolour.
- Motor-sailing by day: a black cone, point down, forward (Rule 25(e)).
- At anchor: an all-round white light forward at night, a black ball by day (Rule 30).
Sound signals
Manoeuvring and warning signals (Rule 34) and signals in restricted visibility (Rule 35):
| Signal | Meaning | Who gives it |
|---|---|---|
| Vessels in sight of one another · rule 34 | ||
| • | I am altering my course to starboard | A power-driven vessel, including a yacht under engine |
| • • | I am altering my course to port | The same |
| • • • | I am operating astern propulsion | The same |
| • • • • • | I do not understand your intentions · the doubt signal | Any vessel; at least five short blasts. Given when it is unclear whether the other vessel is giving way |
| ▬ | Approaching a bend in the channel | A vessel; there is no view round the bend; a vessel coming the other way answers with the same |
| ▬ ▬ • | In a narrow channel: I intend to overtake on your starboard side | The overtaking vessel |
| ▬ ▬ • • | In a narrow channel: I intend to overtake on your port side | The overtaking vessel |
| ▬ • ▬ • | I agree to be overtaken | The vessel being overtaken. If she disagrees or is in doubt — five short blasts |
| Restricted visibility · rule 35 · at least every 2 minutes | ||
| ▬ | A power-driven vessel under way, making way | One prolonged blast |
| ▬ ▬ | A power-driven vessel under way, stopped | Two prolonged blasts about 2 s apart |
| ▬ • • | Sailing · NUC · RAM · constrained by draught · fishing · towing | One prolonged and two short blasts |
| ▬ • • • | A vessel being towed (if manned) | One prolonged and three short blasts, straight after the tug's signal |
| Restricted visibility · rule 35 · at least every 1 minute | ||
| bell | At anchor | Rapid ringing of the bell for about 5 s; a vessel of 100 m or more — the bell forward, then the gong aft. May add • — • (a warning) |
| • • • bell • • • | Aground | Three separate strokes, rapid ringing for about 5 s, three more separate strokes |
• short blast, about 1 second · ▬ prolonged blast, 4–6 seconds
Test yourself
Eight questions from the Skipperium trainer. Choose your answer, then open the explanation.
1. A sailing yacht catches up and overtakes a motor boat. Who gives way?
- The motor boat: power gives way to sail
- The yacht: the overtaking vessel always gives way
- The smaller one
- Nobody: overtaking under sail is forbidden
Show the answer
Correct answer: B — The yacht: the overtaking vessel always gives way
Overtaking (rule 13): the overtaking vessel always gives way — even a sailing vessel overtaking a power-driven one.
2. How do you tell that there is a risk of collision?
- The vessel is bigger and faster than your yacht
- The bearing does not change, the range is closing
- The vessel sounds one short blast
- The bearing is changing, the range is opening
Show the answer
Correct answer: B — The bearing does not change, the range is closing
Risk of collision (rule 7): the direction of the vessel hardly changes while she comes closer — the courses lead to a collision. Check with the compass or against the shore behind her.
3. A yacht is under power with her sails up. What is she under the COLREGs?
- A sailing vessel: the sails are up after all
- A power-driven vessel
- A vessel restricted in her ability to manoeuvre
- The skipper decides depending on the situation
Show the answer
Correct answer: B — A power-driven vessel
Under power a yacht is a power-driven vessel (NL werktuiglijk voortbewogen schip), even with sails up: she gives way to sailing vessels. By day — a black cone point down, by night — masthead light, sidelights and sternlight; the tricolour is switched off.
4. At night a yacht was sailing with the tricolour on and has started the engine. What changes in her lights?
- Nothing changes: the sails are up after all
- Instead of the tricolour: masthead light, sidelights, sternlight
- An all-round red is added to the tricolour
- All lights are switched off except the sternlight
Show the answer
Correct answer: B — Instead of the tricolour: masthead light, sidelights, sternlight
Under engine a yacht is a power-driven vessel: masthead (steaming) light + sidelights + sternlight. The tricolour is for sailing only.
5. What vessel is this?
- A pilot vessel under way
- A trawler, trawling
- A fishing vessel with nets, under way
- A vessel at anchor, seen from the side
Show the answer
Correct answer: B — A trawler, trawling
Green over white — a trawler (green over white — trawling tonight); a red sidelight — we see her port side.
6. What vessel is this?
- A vessel aground, seen from the side
- Not under command, under way
- A pilot vessel under way
- Constrained by draught, under way
Show the answer
Correct answer: B — Not under command, under way
Two all-round reds — not under command; a green sidelight is visible — the vessel is making way and we see her starboard side.
7. What vessel is this?
- A vessel not under command
- A vessel aground
- A minesweeper
- A vessel at anchor
Show the answer
Correct answer: B — A vessel aground
Three balls in a vertical line — aground; at night anchor lights and two reds in a vertical line. A minesweeper's three balls are not in a line: at the masthead and at the ends of the yard.
8. Fog. Which signal does a yacht under sail sound?
- — at least every 2 minutes
- — • • at least every 2 minutes
- — — at least every 2 minutes
- The bell for about 5 s at least every minute
Show the answer
Correct answer: B — — • • at least every 2 minutes
Rule 35: — • • is sounded by sailing vessels, vessels not under command, restricted in ability to manoeuvre, constrained by draught, fishing and towing. A yacht under 12 m may sound some other efficient signal, also at least every 2 minutes.
Frequently asked questions
What does COLREGs mean?
The International Regulations for Preventing Collisions at Sea, 1972 — the rules of the road at sea adopted under the IMO. They apply to all vessels, yachts included, on the high seas and all waters connected to them that seagoing vessels can navigate; some inland waters have rules of their own.
Does sail always have right of way over power?
No. A sailing vessel keeps clear when she is overtaking, of vessels not under command, restricted in their ability to manoeuvre or fishing, and she must not impede large ships in narrow channels and traffic lanes. Under engine she is a power-driven vessel.
What do Rules 5, 6 and 7 say?
Rule 5: keep a proper lookout by sight and hearing and by all available means. Rule 6: always go at a safe speed for the visibility, the traffic and the conditions. Rule 7: use every available means to tell whether a risk of collision exists — if the compass bearing of an approaching vessel does not change appreciably, it does.
What lights does a sailing boat show at night?
Red and green sidelights and a white sternlight — under 20 m they may be combined in a tricolour at the masthead. Under engine she shows a white masthead light as well, like any power-driven vessel, and never the tricolour.
What do two red lights one above the other mean?
A vessel not under command — she cannot get out of your way (Rule 27(a)). Together with white anchor lights they mean a vessel aground (Rule 30(d)).
What is the stand-on vessel?
The vessel that keeps her course and speed while the other — the give-way vessel — keeps clear. She must still act if a collision can no longer be avoided by the give-way vessel alone (Rule 17).
Where can I read the full text of the COLREGs?
The official text is published by the IMO; national maritime authorities and nautical almanacs publish it too, often together with the national rules for inland waters.
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