Introduction
The International Regulations for Preventing Collisions at Sea (COLREGS), formally adopted in 1972 and in force since 1977, are the "rules of the road" for every vessel on international waters. In U.S. inland waters they are supplemented by the Inland Navigation Rules (33 CFR Part 83), which govern lakes, rivers, harbours, and other inland waters inside the COLREGS Demarcation Lines.
Rule 2 — Responsibility: Nothing in these Rules shall exonerate any vessel, or the owner, master, or crew thereof, from the consequences of any neglect to comply with these Rules or of the neglect of any precaution which may be required by the ordinary practice of seamen, or by the special circumstances of the case.
Part A — General (Rules 1–3)
Rule 1 — Application
These Rules apply to all vessels upon the high seas and in all waters connected therewith navigable by seagoing vessels. Inland Rules apply inside the COLREGS Demarcation Lines established by the U.S. Coast Guard.
Rule 2 — Responsibility
Owners, masters, and crews must comply with these Rules and exercise the ordinary precautions required by good seamanship. Nothing in the Rules relieves any vessel of the consequences of neglect, nor of special precautions required by the circumstances.
Rule 3 — General Definitions
- Vessel — every watercraft used or capable of being used as a means of transportation on water.
- Power-driven vessel — any vessel propelled by machinery.
- Sailing vessel — any vessel under sail, provided propelling machinery is not being used.
- Vessel engaged in fishing — any vessel fishing with nets, lines, or trawls that restrict maneuverability (not trolling lines).
- Seaplane — any aircraft designed to maneuver on water.
- Vessel not under command (NUC) — unable to maneuver as required by these Rules due to some exceptional circumstance.
- Vessel restricted in ability to maneuver (RAM) — work limits ability to keep out of the way (dredging, surveying, underwater operations, replenishment at sea, launching/recovering aircraft, minesweeping, towing).
- Vessel constrained by her draft — due to available depth, severely restricted in ability to deviate from her course.
- Underway — not at anchor, made fast to the shore, or aground.
- Making way — moving through the water (underway but not necessarily moving).
- Restricted visibility — any condition limiting sight by fog, mist, falling snow, heavy rain, sandstorms, or similar causes.
- Wing-in-ground (WIG) craft — multimodal craft that, in its main operational mode, flies close to the surface by utilizing surface-effect action.
Part B — Steering and Sailing Rules
Section I — Conduct of Vessels in Any Condition of Visibility (Rules 4–10)
Rule 4 — Application
Rules in this Section (4–10) apply in any condition of visibility.
Rule 5 — Look-out
Every vessel shall at all times maintain a proper look-out by sight and hearing, and by all available means appropriate to the prevailing circumstances and conditions, so as to make a full appraisal of the situation and of the risk of collision.
Rule 6 — Safe Speed
Every vessel shall at all times proceed at a safe speed so that she can take proper and effective action to avoid collision and be stopped within a distance appropriate to the prevailing circumstances. Factors include:
- State of visibility
- Traffic density
- Maneuverability of the vessel (stopping distance and turning ability)
- Presence of background light at night
- Proximity of navigational hazards
- Draft in relation to available water depth
- For vessels with operational radar: range and resolution, sea state/weather effects, and number, location, and movement of detected vessels
Rule 7 — Risk of Collision
Every vessel shall use all available means appropriate to the prevailing circumstances to determine if risk of collision exists. If there is any doubt, such risk shall be deemed to exist. Risk shall be deemed to exist if the compass bearing of an approaching vessel does not appreciably change. A large vessel or a vessel towing at close range may constitute risk even with an appreciable bearing change.
Rule 8 — Action to Avoid Collision
Any action taken to avoid collision shall, if circumstances permit:
- Be positive, made in ample time, and with due regard to good seamanship.
- Be large enough to be readily apparent to another vessel observing visually or by radar.
- Result in passing at a safe distance.
- Not result in another close-quarters situation.
If necessary to avoid collision or allow more time to assess the situation, a vessel shall slacken speed or take all way off by stopping or reversing means of propulsion.
Rule 9 — Narrow Channels
A vessel proceeding along the course of a narrow channel or fairway shall keep as near to the outer limit of the channel on her starboard side as is safe and practicable. A vessel less than 20 m in length or a sailing vessel shall not impede a vessel that can navigate only within a narrow channel or fairway. A vessel engaged in fishing shall not impede the passage of any other vessel navigating within a narrow channel. No vessel shall cross a narrow channel if doing so impedes a vessel which can safely navigate only within such channel.
Rule 10 — Traffic Separation Schemes
Vessels shall use the appropriate traffic lane and proceed in the general direction of traffic flow for that lane. Vessels shall join or leave a traffic lane at the termination point of the lane or at a right angle to the general direction of traffic flow. Vessels less than 20 m in length and sailing vessels shall not impede power-driven vessels following a traffic lane. A vessel engaged in fishing shall not impede the passage of any vessel following a traffic separation scheme.
Section II — Conduct of Vessels in Sight of One Another (Rules 11–18)
Rule 11 — Application
Rules in this Section (11–18) apply to vessels in sight of one another.
Rule 12 — Sailing Vessels
When two sailing vessels are approaching one another:
- When each has the wind on a different side, the vessel with wind on the port side gives way.
- When both have the wind on the same side, the windward vessel gives way.
- If a vessel with wind on the port side sees a vessel to windward and cannot determine whether the other has wind on the port or starboard side, she shall keep out of the way.
The windward side is the side opposite to the side on which the mainsail is carried.
Rule 13 — Overtaking
Any vessel overtaking any other shall keep out of the way of the vessel being overtaken. A vessel is overtaking when coming up with another vessel from a direction more than 22.5° abaft the other's beam. When in doubt whether overtaking, the vessel shall assume she is overtaking and act accordingly. No subsequent alteration of the bearing between the two vessels shall make the overtaking vessel a crossing vessel.
Rule 14 — Head-on Situation
When two power-driven vessels are meeting on reciprocal or nearly reciprocal courses so as to involve risk of collision, each vessel shall alter her course to starboard so that each passes on the port side of the other. This situation exists when a vessel sees another ahead or nearly ahead. When in doubt, this situation shall be deemed to exist and action taken accordingly.
Rule 15 — Crossing Situation
When two power-driven vessels are crossing so as to involve risk of collision, the vessel which has the other on her starboard side shall give way and shall, if circumstances permit, avoid crossing ahead of the other vessel.
Memory aid: "If to starboard red appear, 'tis your duty to keep clear."
Rule 16 — Action by Give-way Vessel
Every vessel which is directed to keep out of the way of another vessel shall, so far as possible, take early and substantial action to keep well clear.
Rule 17 — Action by Stand-on Vessel
The stand-on vessel shall keep her course and speed. When it becomes apparent that the give-way vessel is not taking appropriate action, the stand-on vessel may take action to avoid collision by her maneuver alone. When collision cannot be avoided by the action of the give-way vessel alone, the stand-on vessel shall take such action as will best aid to avoid collision. The stand-on vessel is not permitted to alter course to port for a vessel on her own port side (in a crossing situation).
Rule 18 — Responsibilities Between Vessels
Except where Rules 9, 10, and 13 otherwise require, the order of precedence is:
| Must give way to… | Notes |
|---|---|
| Vessel not under command (NUC) | Highest priority — cannot maneuver |
| Vessel restricted in ability to maneuver (RAM) | Dredges, survey vessels, minesweepers, etc. |
| Vessel constrained by draft | Deep-draft ships in confined channels |
| Vessel engaged in fishing | Only when gear is deployed; not trolling |
| Sailing vessel | Power-driven gives way to sail (except Rules 9, 10, 13) |
| Power-driven vessel | Lowest priority among underway vessels |
A seaplane shall, in general, keep well clear of all vessels and avoid impeding navigation. In a close-quarters situation, the seaplane shall comply with the Rules for power-driven vessels.
Section III — Conduct of Vessels in Restricted Visibility (Rule 19)
Rule 19 — Conduct of Vessels in Restricted Visibility
This rule applies to vessels not in sight of one another when navigating in or near an area of restricted visibility:
- Proceed at a safe speed adapted to the prevailing conditions.
- Have engines ready for immediate maneuver.
- Have due regard to the prevailing circumstances, including the limitations of radar.
- On hearing a fog signal apparently forward of the beam: reduce speed to the minimum at which she can be kept on her course. Take all way off if necessary. Navigate with extreme caution until danger of collision is over.
- Avoid, as far as possible, an alteration of course to port for a vessel forward of the beam.
Part C — Lights and Shapes (Rules 20–31)
Rule 20 — Application
Rules in this part apply in all weathers. They apply from sunset to sunrise. During restricted visibility they shall be complied with during the day. Shapes are required between sunrise and sunset.
Rule 21 — Definitions
- Masthead light — white light, 225° arc, visible 5–6 nm, placed forward.
- Sidelights — green (starboard) and red (port), each 112.5° arc, visible 2–3 nm.
- Stern light — white light, 135° arc, visible 2–3 nm, placed aft.
- Towing light — yellow light, same arc as stern light (135°).
- All-round light — 360° arc.
- Flashing light — flashing at regular intervals at a rate of 120 or more flashes per minute.
Rule 22 — Visibility of Lights
| Vessel length | Masthead | Sidelights | Stern / towing | All-round |
|---|---|---|---|---|
| 50 m or more | 6 nm | 3 nm | 3 nm | 3 nm |
| 12–50 m | 5 nm | 2 nm | 2 nm | 2 nm |
| Under 12 m | 2 nm | 1 nm | 2 nm | 2 nm |
| Inconspicuous partly submerged vessel or object | — | — | — | 3 nm |
Rule 23 — Power-driven Vessels Underway
A power-driven vessel underway shall exhibit:
- A masthead light forward.
- A second masthead light abaft of and higher than the forward one (required for vessels 50 m or more in length; optional for shorter vessels).
- Sidelights (red port, green starboard).
- A stern light.
A vessel under 7 m whose maximum speed does not exceed 7 knots may instead exhibit an all-round white light and, if practicable, sidelights. A vessel under 12 m may combine sidelights in a single lantern on the centerline.
Rule 24 — Towing and Pushing
Towing astern: masthead lights (two in a vertical line, or three if tow length exceeds 200 m), sidelights, stern light, and a towing light (yellow) in a vertical line above the stern light.
Pushing or towing alongside: two masthead lights in a vertical line, sidelights, and stern light.
Vessel being towed: sidelights and stern light. If tow exceeds 200 m, an all-round white light or a diamond shape by day.
When a pushing vessel and pushed vessel are rigidly connected, they are regarded as one power-driven vessel.
Rule 25 — Sailing Vessels Underway and Vessels Under Oars
A sailing vessel underway shall exhibit sidelights and a stern light. Sidelights may be combined in one lantern at the top of the mast. A sailing vessel may also exhibit, at the top of the mast, two all-round lights (red over green). A sailing vessel of less than 7 m shall, if practicable, exhibit those lights; otherwise shall have an electric torch or lighted lantern ready to hand showing a white light. A vessel under oars may exhibit the lights for sailing vessels or shall have ready an electric torch showing a white light.
Rule 26 — Fishing Vessels
A vessel engaged in fishing shall exhibit:
- Two all-round lights vertically: green over white (trawling) or red over white (other fishing).
- When making way: also sidelights and stern light.
- If outlying gear extends more than 150 m from the vessel: an all-round white light in the direction of the gear.
A vessel of less than 20 m engaged in fishing may exhibit a basket shape by day instead of the prescribed shapes below, and may exhibit the lights prescribed for vessels under 20 m engaged in fishing at night.
Rule 27 — Vessels Not Under Command or Restricted in Ability to Maneuver
Vessel not under command (NUC): two all-round red lights in a vertical line; when making way, also sidelights and stern light. By day, two balls in a vertical line.
Vessel restricted in ability to maneuver (RAM): three all-round lights in a vertical line (red–white–red); when making way, also masthead lights, sidelights, and stern light. By day, ball–diamond–ball in a vertical line.
Vessel engaged in dredging or underwater operations: RAM lights/shapes plus two all-round red lights or two balls on the obstructed side and two all-round green lights or two diamonds on the clear side.
Vessel engaged in diving operations: RAM lights/shapes plus a rigid replica of the Code flag "A" not less than 1 m in height.
Vessel engaged in minesweeping: RAM lights plus three all-round green lights arranged in an "L" shape — or three balls by day.
Rule 28 — Vessels Constrained by Their Draft
A vessel constrained by her draft may, in addition to the lights prescribed for power-driven vessels, exhibit three all-round red lights in a vertical line, or a cylinder by day.
Rule 29 — Pilot Vessels
A vessel engaged in pilotage duty shall exhibit at the masthead two all-round lights in a vertical line (white over red), and when underway also sidelights and a stern light; when at anchor, also an anchor light. A vessel not engaged in pilotage duty shall not exhibit these lights.
Rule 30 — Anchored Vessels and Vessels Aground
At anchor: in the fore part, an all-round white light or a ball; and at or near the stern and at a lower level, an all-round white light. Vessels under 50 m may exhibit one all-round white light anywhere. Vessels under 7 m at anchor away from a narrow channel, fairway, or anchorage need not exhibit anchor lights or shapes.
Aground: anchor lights/shapes plus two all-round red lights in a vertical line, or three balls in a vertical line.
Rule 31 — Seaplanes and WIG Craft
A seaplane or WIG craft unable to exhibit lights and shapes of the required characteristics shall exhibit lights and shapes as closely similar as possible.
Part D — Sound and Light Signals (Rules 32–37)
Rule 32 — Definitions
- Whistle — any sound-signaling appliance capable of producing the prescribed blasts.
- Short blast — a blast of about one second duration.
- Prolonged blast — a blast of four to six seconds duration.
Rule 33 — Equipment for Sound Signals
| Vessel length | Required equipment |
|---|---|
| 100 m or more | Whistle, bell, and gong |
| 12–100 m | Whistle and bell |
| Under 12 m | Any sound-signaling device |
Rule 34 — Maneuvering and Warning Signals
Power-driven vessels in sight of one another — whistle signals:
| Signal | Meaning (International) |
|---|---|
| One short blast | I am altering my course to starboard |
| Two short blasts | I am altering my course to port |
| Three short blasts | My engines are going astern |
| Five or more short blasts | Danger signal — I do not understand your intentions |
Inland Rules addition: When vessels agree to pass, the initiating vessel signals two prolonged + one short (overtake starboard) or two prolonged + two short (overtake port); the other vessel signals one prolonged + one short + one prolonged + one short to signal agreement.
Light signals: a vessel may supplement whistle signals with light flashes — one flash = starboard, two flashes = port, three flashes = astern. Intervals between flashes approximately one second; sequence not less than ten seconds apart. Lights must be an all-round white light visible at least 5 nm.
Rule 35 — Sound Signals in Restricted Visibility
| Vessel | Signal | Interval |
|---|---|---|
| Power-driven, making way | One prolonged blast | Every 2 min |
| Power-driven, underway but stopped (not making way) | Two prolonged blasts (2 sec apart) | Every 2 min |
| NUC, RAM, constrained by draft, sailing, fishing, or towing/pushing | One prolonged + two short blasts | Every 2 min |
| Last vessel of a tow (if manned) | One prolonged + three short blasts | Every 2 min |
| Vessel at anchor (< 100 m) | Rapid bell ringing for about 5 seconds | Every 1 min |
| Vessel at anchor (≥ 100 m) | Rapid bell (forward) 5 sec, then gong (aft) 5 sec | Every 1 min |
| Vessel aground | Bell signal + 3 distinct strokes before and after | Every 1 min |
| Pilot vessel on duty | Four short blasts (in addition to prescribed signal) | — |
Rule 36 — Signals to Attract Attention
Any vessel may make light or sound signals that cannot be mistaken for any signal authorized elsewhere in the Rules, and shall not shine a light that would dazzle or embarrass another vessel or mislead navigators.
Rule 37 — Distress Signals
Annex IV lists recognized distress signals, including:
- Gun or explosive fired at approximately 1-minute intervals.
- Continuous sounding of any fog-signaling apparatus.
- Rockets or shells throwing red stars, fired one at a time at short intervals.
- Orange smoke signal.
- Slowly and repeatedly raising and lowering outstretched arms.
- Radiotelegraph alarm signal (SOS) / radiotelephone alarm signal / "MAYDAY" on channel 16.
- EPIRB activation.
- Orange-colored flag with black square and circle (Code flag N over C).
- Dye marker.
- Flames on a vessel (burning tar barrel, oil barrel, etc.).
- A square shape with a ball above or below it.
- High-intensity white light flashing at 50–70 flashes per minute.
Part E — Exemptions (Rule 38)
Rule 38 — Exemptions
Vessels or classes of vessels that cannot comply with these Rules with respect to lights, shapes, and sound-signal equipment may be exempted if:
- They were built, or in the case of lights or shapes, fitted before the Rules entered into force (1977), and
- Compliance with the Rules would require retrofitting that is not readily practicable.
Exemptions are subject to specified time limits and apply only to the extent that compliance would require structural changes to the vessel. All exemptions must be noted in the vessel's log and reported to the relevant authority.
Key Memory Aids
- Red + Port + Left — sidelight is red; remember "port wine is red."
- "If to starboard red appear, 'tis your duty to keep clear" — crossing Rule 15.
- Pecking order (Rule 18): NUC → RAM → Constrained by Draft → Fishing → Sailing → Power.
- One blast = starboard, Two blasts = port, Three blasts = backing, Five = danger.
- Fog signals: one prolonged = making way under power; two prolonged = stopped; one prolonged + two short = everything else (NUC, sailing, fishing, towing).
- Lights color at anchor: all-round white. At anchor aground: add two all-round red.
- Trawling = green over white; other fishing = red over white.
Additional Resources
- U.S. Coast Guard Navigation Center: navcen.uscg.gov
- Full COLREGS text (IMO): imo.org
- U.S. Inland Navigation Rules: 33 CFR Part 83
- U.S. Coast Guard Boating Safety: uscgboating.org