COLREGs explained simply: the International Regulations for Preventing Collisions at Sea are the rules of the road for everyone afloat. They apply to vessels on the high seas and connected waters, and for any watchkeeper they are not optional. Here is the plain-English version.
Key points
- Every encounter comes down to two roles: give-way and stand-on.
- Rules 5, 6, 7 and 8 (lookout, safe speed, risk of collision, action to avoid collision) underpin everything else.
- Rule 18 sets the pecking order: the less manoeuvrable the vessel, the more right of way it has.
- Lights and shapes tell you what a vessel is doing, and mnemonics make them stick.
- Repetition is what makes the rules stay in your head, so use dead time on watch.
COLREGs explained: give-way and stand-on
Almost every encounter comes down to two roles. The give-way vessel is the one required to take early, obvious action to keep clear. The stand-on vessel holds its course and speed so the other can predict what it will do. If it becomes clear that the give-way vessel is not acting, the stand-on vessel may act to avoid collision, and must do so when collision cannot be avoided by the give-way vessel alone. Knowing which one you are is the whole game.
The pecking order
When two vessels could collide, the rules set out who keeps clear of whom. Loosely, the less manoeuvrable a vessel is, the more right of way it has:
The COLREGs pecking order (Rule 18)
Higher in the list = others keep out of its way. Each vessel keeps clear of every vessel above it.
- Not under command (NUC) and restricted in ability to manoeuvre (RAM)
- Constrained by her draught (CBD): other vessels (except NUC and RAM) should, if circumstances allow, avoid impeding her safe passage
- Vessels engaged in fishing
- Sailing vessels
- Power-driven vessels: keep clear of everything above
Remember: Rule 18 sits under Rules 9, 10 and 13. An overtaking vessel always keeps clear, and small or sailing vessels must not impede vessels that can only navigate safely within a narrow channel or traffic lane.
So a power-driven vessel gives way to almost everyone, while a vessel not under command or restricted in its ability to manoeuvre is near the top. Two caveats an examiner will probe: the overtaking rule (Rule 13) applies whatever the vessel types, and a vessel constrained by her draught is still a power-driven vessel in other respects.
The key rules worth knowing by name
- Rule 5, Lookout. Keep a proper lookout by sight and hearing, and by all available means, at all times. Failing to keep one is a factor in many collisions.
- Rule 6, Safe speed. Go at a speed that lets you take proper and effective action, and stop within a distance appropriate to the conditions.
- Rule 7, Risk of collision. If in doubt, assume risk exists. A steady compass bearing with decreasing range means risk of collision.
- Rule 8, Action to avoid collision. Make it early, make it obvious, and make it large enough to be seen by the other vessel.
- Rule 13, Overtaking. The overtaking vessel keeps clear, whatever type it is. A vessel is overtaking when it comes up from more than 22.5 degrees abaft the beam.
- Rule 14, Head-on. Two power-driven vessels meeting head-on, or nearly so, both alter to starboard and pass port to port.
- Rule 15, Crossing. When two power-driven vessels cross, the one that has the other on her own starboard side gives way.
- Rule 18, Responsibilities between vessels. This is the pecking order written down.
Lights and shapes
At night a vessel tells you what it is and what it is doing through its lights; by day, through shapes. Learning them feels daunting until you group them and lean on a few mnemonics. These rhymes are worth their weight in gold on a dark watch:
By day the same information comes from shapes: a ball means at anchor, two cones apex to apex means fishing, a cylinder means constrained by her draught, and so on. Master the lights and the day shapes follow naturally. For more, see navigation lights explained.
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Sound signals
When vessels are in sight of one another, short blasts tell other vessels what you are doing with your helm: one short blast means "I am altering my course to starboard", two means "to port" and three means "my engines are going astern". Five or more short, rapid blasts is the danger signal, meaning "I do not understand your intentions" or "I doubt that you are taking sufficient action to avoid collision". In restricted visibility the signals change (Rule 35): a power-driven vessel making way sounds one prolonged blast at intervals of not more than two minutes, and two prolonged blasts if underway but stopped.
Why crew struggle, and what fixes it
People find the COLREGs hard for honest reasons: there are a lot of rules, they involve visualising vessels moving in three dimensions, and most crew do not apply them often enough to keep them fresh. The fix is repetition in a format you will actually use. Hearing the rules read aloud, again and again, is one of the most effective ways to make them stick.
Frequently asked questions
What does COLREGs stand for?
COLREGs stands for the International Regulations for Preventing Collisions at Sea, 1972. They are the internationally agreed rules of the road that vessels must follow to avoid collisions.
What is the difference between a give-way and a stand-on vessel?
The give-way vessel must take early and obvious action to keep clear. The stand-on vessel keeps its course and speed so its movements are predictable, but must still act to avoid collision if the give-way vessel fails to.
What is the order of priority in COLREGs?
Under Rule 18, a power-driven vessel keeps out of the way of vessels not under command, vessels restricted in their ability to manoeuvre, vessels engaged in fishing and sailing vessels. A sailing vessel keeps out of the way of the first three, and a fishing vessel keeps out of the way of the first two, so it runs from least to most manoeuvrable. Rule 18 applies except where Rules 9 (narrow channels), 10 (traffic separation schemes) and 13 (overtaking) say otherwise, and any vessel other than one not under command or restricted in her ability to manoeuvre must avoid impeding a vessel constrained by her draught.
What do five short blasts mean?
Five or more short, rapid blasts is the danger signal, meaning a vessel does not understand another's intentions or doubts whether enough action is being taken to avoid a collision.
How can I learn the COLREGs quickly?
Repetition in a format you will actually use is the key. Many crew find listening to the rules read aloud, alongside mnemonics for lights and shapes, far more effective than reading the text once.
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