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The Convention on the International Regulations for Preventing Collisions at Sea, 1972 (commonly "COLREGs"), entered into force on 15 July 1977. They apply to all vessels on the high seas and in waters connected to them navigable by seagoing vessels. This page indexes the 38 rules with one-line summaries — for any actual decision on watch, consult the full text and the relevant Annexes (I lights positions, II fishing close-by, III equipment, IV distress signals).
The rules are organised into five parts. Most of the day-to-day work is in Part B (steering and sailing), Part C (lights and shapes), and Part D (sound signals).
Rules 1–3 — application, responsibility, definitions.
Apply to all vessels on the high seas and connecting waters navigable by seagoing vessels. Local authorities may make special rules for inland waters consistent with these.
Nothing exonerates any vessel from the consequences of neglecting these rules or any precaution required by ordinary practice or special circumstance. Departures permitted only to avoid immediate danger.
Defines vessel, power-driven, sailing, fishing, NUC (not under command), RAM (restricted in ability to manoeuvre), constrained by draft, underway, length and breadth, and restricted visibility.
Rules 4–19 — conduct of vessels in any condition of visibility, in sight of one another, and in restricted visibility.
Section I (Rules 4–10) applies in any condition of visibility.
Every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate to the prevailing conditions.
Every vessel shall proceed at a safe speed so that she can take proper and effective action to avoid collision and stop within a distance appropriate to the circumstances and conditions.
Use all available means to determine if risk exists; if there is any doubt, such risk shall be deemed to exist. Compass bearings of an approaching vessel that do not appreciably change indicate risk of collision.
Action shall be positive, made in ample time, and with due regard to good seamanship. Alterations of course and/or speed shall be large enough to be readily apparent to another vessel observing visually or by radar.
Vessels shall keep as near to the outer limit of the channel which lies on her starboard side as is safe and practicable. Vessels of less than 20 m or sailing vessels shall not impede the passage of a vessel that can safely navigate only within the channel.
Conduct in IMO-adopted TSS: proceed in the appropriate lane, keep clear of the separation line, join/leave at the termination, cross at as nearly a right angle as practicable.
Section II (Rules 11–18) applies to vessels in sight of one another.
When two sailing vessels meet: port-tack vessel keeps clear of starboard-tack; if both on the same tack, the windward vessel keeps clear of the leeward.
Any vessel overtaking any other shall keep out of the way of the vessel being overtaken. Overtaking is approaching from more than 22.5° abaft her beam.
When two power-driven vessels meet on reciprocal or nearly reciprocal courses so as to involve risk of collision, each shall alter course to starboard so that each passes on the port side of the other.
When two power-driven vessels are crossing so as to involve risk of collision, the vessel which has the other on her own starboard side shall keep out of the way and shall avoid crossing ahead.
Every vessel directed to keep out of the way shall, so far as possible, take early and substantial action to keep well clear.
The vessel with right of way shall keep her course and speed, but may take action to avoid collision when it becomes apparent the give-way vessel is not taking appropriate action. Last-resort action by the stand-on vessel: not alter to port for a vessel on her own port side.
Hierarchy of priority (each lower must keep clear of all above): NUC > RAM > constrained by draft > fishing > sailing > power-driven. Seaplanes and WIG craft keep clear of all of the above.
Vessels not in sight of one another. Proceed at safe speed adapted to the prevailing circumstances. If a close-quarters situation is developing or risk of collision exists from a vessel forward of the beam, alter course — avoid an alteration to port for a vessel forward of the beam other than one being overtaken.
Rules 20–31 — what to display from sunset to sunrise (and in restricted visibility), and the day shapes that supplement them.
Lights to be exhibited from sunset to sunrise and during such times in restricted visibility. Day shapes exhibited by day.
Defines masthead, sidelight, sternlight, towing light, all-round light, flashing light. Sectors and visibility ranges specified per length.
Minimum range: 6 nm masthead (≥ 50 m), 5 nm masthead (12–50 m), 3 nm sidelights, 2 nm sternlight (vessels under 12 m have reduced minima).
Masthead light forward, sidelights, sternlight. Vessels ≥ 50 m: a second masthead light abaft and higher than the forward one.
Two masthead lights in a vertical line (or three if tow > 200 m), sidelights, sternlight, and a yellow towing light above the sternlight. By day a diamond shape if tow > 200 m.
Sidelights and sternlight. Optionally an all-round red over an all-round green at the masthead. Vessels < 7 m may show a torch.
Trawling: all-round green over all-round white. Other fishing: all-round red over all-round white plus a white light marking outlying gear if it extends > 150 m.
NUC: two all-round red in a vertical line, plus sidelights and sternlight when making way. RAM: red-white-red in a vertical line.
Three all-round red lights in a vertical line, in addition to lights for power-driven vessels. By day: a cylinder.
All-round white over all-round red at or near the masthead, plus sidelights and sternlight when underway. At anchor, anchor lights additionally.
At anchor: all-round white forward, plus a second aft and lower if ≥ 50 m. Aground: anchor lights plus two all-round red in a vertical line. Vessels < 7 m at anchor not in a fairway need not show anchor lights.
Where it is impracticable to display lights conforming to characteristics or positions, lights shall be displayed as closely conforming as possible.
Rules 32–37 — equipment, manoeuvring and warning, restricted visibility, attention, distress.
Defines whistle, short blast (~1 s), prolonged blast (4–6 s).
Vessels ≥ 12 m to carry a whistle; vessels ≥ 20 m to carry a bell; vessels ≥ 100 m additionally a gong of different tone forward. Vessels < 12 m to have some means of efficient sound signal.
One short = altering to starboard; two short = altering to port; three short = astern propulsion; five or more short = doubt. Overtaking signals in narrow channels: ——• starboard, ——•• port, —•—• consent.
Sounded at intervals of not more than 2 minutes. — power-driven making way; —— power-driven stopped; —•• NUC/RAM/CBD/sailing/fishing/towing; bell at anchor (gong aft if ≥ 100 m).
Any vessel may make light or sound signals that cannot be mistaken for any signal authorised elsewhere in the rules, but not strobe lights.
When in distress and requiring assistance, a vessel shall use or exhibit signals described in Annex IV. (See also the distress reference page.)
Rule 38 — phased exemptions for vessels constructed before the convention entered into force.
Vessels (including their lights and shapes) constructed before specified dates and conforming to the 1960 International Regulations may continue under the older standards until specified deadlines, mostly long expired.
This summary is for quick reference only. The authoritative text is the IMO publication Convention on the International Regulations for Preventing Collisions at Sea, 1972, as amended.