COLREGS quick reference

The Rules apply to all vessels on the high seas and in all connected navigable waters. Special rules may be made by an authority for harbors, rivers, and inland waters.

Nothing exonerates you from the consequences of neglect. Give due regard to all dangers of navigation and special circumstances — including a departure from the Rules when necessary to avoid immediate danger.

Defines the key terms: vessel, power-driven, sailing, engaged in fishing, seaplane, Not Under Command (NUC), Restricted in Ability to Maneuver (RAM), Constrained By Draft, underway, length & breadth, in sight, and restricted visibility.

Rules 4–10 apply in any condition of visibility.

Every vessel must keep a proper look-out by sight and hearing, and by all available means, to fully appraise the situation and the risk of collision.

Proceed at a safe speed so you can take proper, effective action and stop within a distance appropriate to the circumstances — factoring visibility, traffic, maneuverability, and (if fitted) radar.

Use all available means to determine if risk exists. If in doubt, assume it does. Don't rely on scanty information, especially scanty radar.

Any action must be positive, made in ample time, and obvious to another vessel. A course and/or speed change should be large enough to be readily apparent. If necessary, slacken speed or stop.

Keep to the outer limit on your starboard side. Vessels under 20 m, sailing vessels, and those fishing must not impede a vessel that can only navigate within the channel. Special overtaking signals apply.

Proceed in the appropriate lane in the general direction of flow, join and leave at the ends, and avoid crossing lanes — but if you must cross, do so on a heading as nearly as practical at right angles.

Rules 11–18 apply to vessels in sight of one another.

When two sailing vessels risk collision: the one with the wind on the port side gives way; if both have wind on the same side, the windward vessel gives way.

Any vessel overtaking (approaching from more than 22.5° abaft the beam) must keep out of the way of the vessel being overtaken, regardless of the later rules.

Two power-driven vessels meeting nearly head-on each alter course to starboard so they pass port-to-port.

When two power-driven vessels cross, the vessel with the other on her own starboard side gives way and avoids crossing ahead of her.

Take early and substantial action to keep well clear.

Keep your course and speed. You may take action if the give-way vessel isn't, and you must act when collision cannot be avoided by her action alone. A power-driven stand-on vessel should avoid turning to port for a vessel on her own port side.

The pecking order: a power-driven vessel keeps clear of sailing, fishing, RAM, and NUC vessels; a sailing vessel keeps clear of fishing, RAM, and NUC vessels; and so on up the hierarchy.

For vessels not in sight of one another in or near restricted visibility: safe speed, engine ready. If a close-quarters situation develops, avoid altering to port for a vessel forward of the beam (other than one being overtaken), and avoid altering toward a vessel abeam or abaft the beam.

Lights must be shown from sunset to sunrise and in restricted visibility; shapes are shown by day. Comply in all weathers.

Defines masthead light, sidelights, sternlight, towing light, all-round light, and flashing light — including the arcs of visibility for each.

Required minimum ranges depend on vessel length (e.g., longer vessels show lights visible at greater distances).

Masthead light(s) forward, sidelights, and a sternlight (smaller vessels and air-cushion craft have variations).

Towing vessels show additional masthead lights in a vertical line and a yellow towing light; the configuration signals the length of the tow.

Sidelights and a sternlight; optionally two all-round lights at the masthead, red over green. Vessels under oars may show a torch.

Trawling shows green over white all-round lights; other fishing shows red over white, plus a light or shape toward outlying gear.

Not Under Command shows two all-round red lights; Restricted in Ability to Maneuver shows red-white-red. Dredging and diving operations have their own configurations.

May show three all-round red lights in a vertical line, or a cylinder by day.

A vessel on pilotage duty shows white over red all-round lights at the masthead — 'white over red, pilot ahead.'

At anchor: all-round white light(s) and a ball by day. Aground: the anchor lights plus two all-round red lights (or three balls by day).

Where impracticable to show lights of the prescribed characteristics, exhibit lights as closely similar as possible.

Defines whistle, short blast (about 1 second), and prolonged blast (4–6 seconds).

Vessels are required to carry a whistle, and (above a certain length) a bell and gong.

One short blast = I am altering to starboard; two short = altering to port; three short = operating astern propulsion; five or more short, rapid = doubt or danger. Special bend/overtaking signals apply in narrow channels.

Patterns of prolonged and short blasts identify a vessel's status (making way, underway but stopped, towing, fishing, RAM, etc.) and are sounded at intervals.

A vessel may make light or sound signals to attract attention, provided they can't be mistaken for any signal in the Rules.

When in distress and requiring assistance, use the signals described in Annex IV (flares, Mayday, etc.).

Provides phase-in / grandfather provisions for vessels built before the Rules came into force, for certain equipment and light-placement requirements.