Rules of the Road
COLREGS quick reference
Plain-English summaries of all 38 International Navigation Rules, anchored by number for fast lookup. This is a study aid — the exam tests the exact wording, so confirm against the official text. Rules of the Road is the module you must score 90% on, so know these cold.
Part A — General (Rules 1–3)
Rule 1 — Application
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.
Rule 2 — Responsibility
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.
Rule 3 — General Definitions
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.
Part B — Steering & Sailing (Rules 4–19)
Rule 4 — Application
Rules 4–10 apply in any condition of visibility.
Rule 5 — Look-out
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.
Rule 6 — Safe Speed
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.
Rule 7 — Risk of Collision
Use all available means to determine if risk exists. If in doubt, assume it does. Don't rely on scanty information, especially scanty radar.
Rule 8 — Action to Avoid Collision
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.
Rule 9 — Narrow Channels
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.
Rule 10 — Traffic Separation Schemes
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.
Rule 11 — Application
Rules 11–18 apply to vessels in sight of one another.
Rule 12 — Sailing Vessels
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.
Rule 13 — Overtaking
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.
Rule 14 — Head-on Situation
Two power-driven vessels meeting nearly head-on each alter course to starboard so they pass port-to-port.
Rule 15 — Crossing Situation
When two power-driven vessels cross, the vessel with the other on her own starboard side gives way and avoids crossing ahead of her.
Rule 16 — Action by the Give-way Vessel
Take early and substantial action to keep well clear.
Rule 17 — Action by the Stand-on Vessel
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.
Rule 18 — Responsibilities Between Vessels
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.
Rule 19 — Conduct in Restricted Visibility
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.
Part C — Lights & Shapes (Rules 20–31)
Rule 20 — Application
Lights must be shown from sunset to sunrise and in restricted visibility; shapes are shown by day. Comply in all weathers.
Rule 21 — Definitions
Defines masthead light, sidelights, sternlight, towing light, all-round light, and flashing light — including the arcs of visibility for each.
Rule 22 — Visibility of Lights
Required minimum ranges depend on vessel length (e.g., longer vessels show lights visible at greater distances).
Rule 23 — Power-driven Vessels Underway
Masthead light(s) forward, sidelights, and a sternlight (smaller vessels and air-cushion craft have variations).
Rule 24 — Towing & Pushing
Towing vessels show additional masthead lights in a vertical line and a yellow towing light; the configuration signals the length of the tow.
Rule 25 — Sailing Vessels & Vessels Under Oars
Sidelights and a sternlight; optionally two all-round lights at the masthead, red over green. Vessels under oars may show a torch.
Rule 26 — Fishing Vessels
Trawling shows green over white all-round lights; other fishing shows red over white, plus a light or shape toward outlying gear.
Rule 27 — NUC & RAM Vessels
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.
Rule 28 — Vessels Constrained by Draft
May show three all-round red lights in a vertical line, or a cylinder by day.
Rule 29 — Pilot Vessels
A vessel on pilotage duty shows white over red all-round lights at the masthead — 'white over red, pilot ahead.'
Rule 30 — Anchored Vessels & Vessels Aground
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).
Rule 31 — Seaplanes
Where impracticable to show lights of the prescribed characteristics, exhibit lights as closely similar as possible.
Part D — Sound & Light Signals (Rules 32–37)
Rule 32 — Definitions
Defines whistle, short blast (about 1 second), and prolonged blast (4–6 seconds).
Rule 33 — Equipment for Sound Signals
Vessels are required to carry a whistle, and (above a certain length) a bell and gong.
Rule 34 — Maneuvering & Warning Signals
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.
Rule 35 — Sound Signals in Restricted Visibility
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.
Rule 36 — Signals to Attract Attention
A vessel may make light or sound signals to attract attention, provided they can't be mistaken for any signal in the Rules.
Rule 37 — Distress Signals
When in distress and requiring assistance, use the signals described in Annex IV (flares, Mayday, etc.).
Part E — Exemptions (Rule 38)
Rule 38 — Exemptions
Provides phase-in / grandfather provisions for vessels built before the Rules came into force, for certain equipment and light-placement requirements.
Make them stick
Pair these with the light-identification mnemonics, test yourself in the Rules of the Road bank, and look up any unfamiliar term in the glossary.