What are COLREGs? Who has right of way at sea

What are COLREGs and who do they apply to?

COLREGs (in Spanish, RIPA) are the International Regulations for Preventing Collisions at Sea, 1972: they set the steering and sailing rules, the lights and shapes and the sound signals that stop two vessels from colliding. They bind every vessel on the high seas and in all waters connected to them, including your sailing boat or motorboat close to shore.

It is divided into parts: A (rules 1 to 3) gives the definitions; B (rules 4 to 19), the steering and sailing rules, which decide who keeps clear; C (rules 20 to 31), lights and shapes; and D (rules 32 to 37), sound and light signals.

Two definitions worth getting clear from the start. A sailing vessel is one under sail with her engine not in use: if it is running, for COLREGs you are a power-driven vessel even with sails up. And risk of collision (rule 7): if the compass bearing of an approaching vessel does not change, you are on a collision course; if in doubt, risk is deemed to exist.

Who has right of way at sea?

It depends on the encounter: between two power-driven vessels the overtaking, head-on and crossing rules apply (rules 13, 14 and 15); between two sailing vessels, the wind decides (rule 12); and between different kinds of vessel, the rule 18 hierarchy. Above all, a vessel overtaking another always keeps out of the way.

Crossing: rule 15

The vessel that has the other on her own starboard (right-hand) side gives way. She acts early, usually turning to starboard to pass astern of the other, and avoids crossing ahead of her. The other vessel keeps her course and speed.

At night you can tell at once: if you see the other vessel's red light (her port side), she is on your starboard side and it is your job to keep clear. The stand-on vessel (rule 17) does not just watch, either: if she sees the other is not manoeuvring, she may and must act to avoid the collision.

Head-on: rule 14

It is a head-on situation (rule 14): both alter course to starboard and pass port to port. Neither has priority; both manoeuvre.

At night you recognise it because you see both of the other vessel's sidelights at once, red and green, with her masthead lights in line.

Overtaking: rule 13

Always the overtaking vessel, whatever her type: even a sailing boat overtaking a motorboat (rule 13). You are overtaking when you come up from more than 22.5° abaft the other vessel's beam, inside the arc of her sternlight.

At night the overtaking vessel sees only the other's white sternlight, none of her sidelights. If in doubt whether you are overtaking, assume you are.

Between two sailing vessels: rule 12

When both are under sail, the wind decides: the one with the wind on her port side gives way to the one with it on her starboard side; and if both have it on the same side, the windward boat gives way to the leeward one.

What is the vessel hierarchy in COLREGs?

Rule 18, from most to least privileged: vessel not under command and vessel restricted in her ability to manoeuvre (no order between them), vessel engaged in fishing, sailing vessel and power-driven vessel. Each keeps out of the way of those above it.

1. Vessel not under command (unable to manoeuvre, for example after a breakdown) and vessel restricted in her ability to manoeuvre (a dredger, a vessel doing underwater work, a difficult tow). The rule puts neither above the other.
2. Vessel engaged in fishing: with nets, lines or trawls that restrict her manoeuvrability. A pleasure boat trolling a line does not count.
3. Sailing vessel, under sail only.
4. Power-driven vessel: most pleasure craft.

Separately there is the vessel constrained by her draught, a ship that cannot leave deep water: everyone except the vessel not under command and the one restricted in her ability to manoeuvre avoids impeding her passage.

Does a sailing boat always have right of way over a motorboat?

No. A sailing vessel gives way when she is the one overtaking, must not impede a vessel that can only navigate safely within a narrow channel or a traffic lane, and with her engine running she counts as a power-driven vessel even with sails up.

Rule 18 opens with a proviso that is often forgotten: it applies "except where rules 9 (narrow channels), 10 (traffic separation schemes) and 13 (overtaking) otherwise require". That is why the sailing boat overtaking a motorboat is the one that keeps clear.

How should you manoeuvre to avoid a collision?

Positive, made in ample time and clear (rule 8): an alteration of course or speed large enough for the other vessel to notice, not a series of small adjustments. And you check that it works: the other vessel's bearing must start to change.

If there is room, an early alteration of course is usually the most effective. If you need more time to assess the situation, you slow down or stop. What does not work is a timid, late manoeuvre: the other vessel does not notice it and the bearing stays the same. You can see this in the simulator with the «Sin maniobra» (no manoeuvre) option.

Which navigation lights do you need to know?

The four basic ones: the white masthead light shining forward (225°), the sidelights, green to starboard and red to port (112.5° each), and the white sternlight (135°). They are shown from sunset to sunrise and in restricted visibility.

• Power-driven vessel under 50 m: masthead light, sidelights and sternlight.
• Sailing vessel under sail: sidelights and sternlight, no masthead light (optionally red over green all-round at the masthead). If she starts her engine, she switches on the masthead light.
• Not under command: two all-round red lights in a vertical line.
• Restricted in ability to manoeuvre: red, white, red all-round lights in a vertical line.
• At anchor, under 50 m: one all-round white light.

How to tell at night where another vessel is heading, which lights a sailing boat or a small motorboat shows and how far away they can be seen: it is all, with another simulator, in navigation lights explained. And don't confuse them with the lights of lighthouses and buoys, which are a different subject: buoyage and cardinal marks.

How are COLREGs tested in the Spanish PER exam?

With drawings of two boats, A and B, and four possible answers: who manoeuvres, which situation it is, or which vessel it is from her lights and shapes. In the official Barcelona exam of 20 June 2026 (model 1) they were 10 of the 45 questions, and COLREGs have their own maximum number of mistakes: you can fail on them alone.

The classic mistake: applying the wind rule to a motorboat

This is the question as it appeared in that exam (in Spanish, translated):

"Sailing a power-driven vessel, we see a sailing vessel ahead which, as shown in the drawing, is crossing with risk of collision. What manoeuvre should we make?"

• a) Keep our course and speed because we have right of way.
• b) We will manoeuvre to avoid the collision. (correct)
• c) We will only manoeuvre if the wind is on our starboard side.
• d) We will only manoeuvre if the wind is on our port side.

The right answer is b: the motorboat keeps out of the way of the sailing boat (rule 18). The traps are c and d: the wind-on-port or starboard rule is rule 12, and it only applies between two sailing vessels. A motorboat does not "take the wind" for COLREGs purposes. And option a catches anyone who mixes up a crossing between two motorboats (rule 15) with motor versus sail.

In the online classroom you practise with real official exams from previous sittings, marked instantly. If you are planning your study, see how to pass the PER in a month and how to get the PER licence step by step.

Source: consolidated text of the RIPA (COLREGs) in Spain's BOE (BOE-A-1977-15605) and Topic 6 of Altair's PER syllabus.