What Are the COLREGS?
The International Regulations for Preventing Collisions at Sea (COLREGS, 72 COLREGS, or the "Rules of the Road") are adopted by the IMO and apply to all vessels on the high seas and connected navigable waters. The U.S. also has separate Inland Navigation Rules that apply inside the demarcation lines — they are nearly identical but differ on a few critical points tested on every USCG exam.
Where COLREGS Apply
- ▸High seas (beyond demarcation lines)
- ▸Waters connected to the high seas
- ▸72 COLREGS = International Rules
Where Inland Rules Apply
- ▸Inside U.S. demarcation lines
- ▸Inland rivers, bays, harbors
- ▸Great Lakes, Western Rivers
Key COLREGS vs. Inland Differences
- ▸CBD exists in COLREGS only
- ▸Overtaking signals differ
- ▸Whistle signal meanings differ slightly
Rule 18 — The Pecking Order
Rule 18 defines which type of vessel has the right of way. Vessels higher on the list (lower rank number) have priority. Power-driven vessels are burdened last — they must give way to everything above them. The one override: Rule 13 (overtaking) always supersedes Rule 18 regardless of vessel type.
Not Under Command (NUC)
NUCRight of way over all
2 all-round red lights (vert.), no sidelights when stopped
Restricted in Ability to Maneuver (RAM)
RAMRight of way over all except NUC
Red-white-red vertical all-round lights
Constrained by Draft (CBD)
CBDRight of way over fishing, sailing, power
3 all-round red lights (vert.) — COLREGS only, not Inland
Engaged in Fishing (with gear out)
FISHRight of way over sailing and power
Green-white or red-white depending on gear/speed
Sailing Vessel (sail only, no engine)
SAILRight of way over power-driven vessels
Sidelights and stern light; optional combined red-green masthead
Power-Driven Vessel Underway
PWRBurdened — give way to all above
Masthead, sidelights, stern light
CBD: COLREGS Only — Not Inland
Constrained by Draft (CBD) is unique to the International COLREGS. U.S. Inland Rules have no CBD category. Exam questions on Inland Rules will not include CBD in the pecking order. This is one of the most commonly missed distinctions on the USCG exam.
Rule 13 Override
When a vessel is overtaking under Rule 13, it is the give-way vessel regardless of its type. A sailing vessel overtaking a power-driven vessel must give way to that power vessel. The overtaking rule supersedes the entire Rule 18 pecking order.
Scenario Decision Trees
Use this framework to quickly classify any encounter situation on the exam. Work through the questions in order — overtaking first, then head-on, then crossing, then check for restricted visibility.
Overtaking Scenario (Rule 13)
Rule 13Decision Question
Are you coming from more than 22.5° abaft the other vessel's beam?
YES — You are the OVERTAKING (give-way) vessel regardless of your vessel type.
- ▸Overtaking rule supersedes ALL other rules — even a sailing vessel overtaking a power-driven vessel gives way
- ▸If you see only the stern (white) light of the vessel ahead, you are in the overtaking arc
- ▸When in doubt whether overtaking, assume you are and give way
- ▸You remain the give-way vessel until you are past and clear
Key Signal
INTL: 1 long + 1 short (starboard side pass) or 1 long + 2 short (port side pass), await agreement
Head-On Situation (Rule 14)
Rule 14Exam FavoriteDecision Question
Are you on nearly reciprocal courses with risk of collision?
Both vessels are EQUALLY burdened — both must turn to STARBOARD.
- ▸You see the masthead lights in a vertical line OR both sidelights (red + green) simultaneously
- ▸Both vessels turn to starboard — each passes on the other's port side
- ▸No stand-on vessel in a head-on — the obligation is mutual
- ▸When in doubt whether head-on or crossing, treat it as head-on and turn right
Key Signal
1 short blast (intending to alter course to starboard), wait for agreement before maneuvering
Crossing Situation (Rule 15)
Rule 15Decision Question
Is the other power-driven vessel on your starboard side on an intersecting course?
YES — You are the GIVE-WAY vessel. Keep out of the way.
- ▸You see a RED sidelight on the approaching vessel — red means give way
- ▸Give-way vessel should avoid crossing ahead of the stand-on vessel
- ▸Stand-on vessel (other vessel sees your red): maintain course and speed
- ▸Stand-on vessel may act when give-way is not responding (Rule 17)
- ▸Stand-on vessel must not turn to PORT for a vessel on its own port side
Key Signal
Give-way: alter course substantially to starboard (avoid crossing ahead). 1 short blast if altering to starboard.
Restricted Visibility (Rule 19)
Rule 19Decision Question
Are you in or near an area of restricted visibility?
Rules 12–18 DO NOT APPLY. Both vessels navigate by Rule 19 alone.
- ▸Proceed at safe speed — engines ready for immediate maneuver
- ▸Radar target forward of beam: do NOT alter to port (unless overtaking); consider reducing speed
- ▸Fog signal heard forward of beam: reduce to bare steerageway or stop
- ▸No stand-on vessel in fog — both vessels bear equal responsibility
- ▸Assess risk by radar; do not assume open water from a clean screen
Key Signal
Sound fog signals: power underway — 1 prolonged blast every 2 min; vessel stopped — 2 prolonged blasts every 2 min
Rules Quick-Reference — USCG Exam Essentials
The most-tested rules from Part B (Steering and Sailing Rules) and Part A (General). Memorize the exam angle for each rule — the USCG question bank tests these specific angles repeatedly.
| Rule | Name | Core Requirement | Exam Angle |
|---|---|---|---|
| Rule 2 | Responsibility | Nothing in the rules exonerates a vessel from the consequences of neglect or seamanship. Good seamanship may require departing from the rules to avoid immediate danger. | Can you ever violate COLREGS? Yes — Rule 2 allows departure from rules to avoid danger. |
| Rule 5 | Lookout | Every vessel must at all times maintain a proper lookout by sight and hearing — and by all available means appropriate in the prevailing circumstances. Radar and VHF count. | What counts as a lookout? ALL available means — not just visual. |
| Rule 6 | Safe Speed | Every vessel must proceed at a safe speed to allow proper action to avoid collision and stop in the distance appropriate to prevailing circumstances and visibility. | Factors: visibility, traffic density, maneuverability, radar range scale, background light, sea state, proximity of hazards. |
| Rule 7 | Risk of Collision | Use all available means to determine risk. Steady compass bearing + decreasing range = risk of collision. Scanty info must not be assumed to mean no risk. | Primary method: take a series of compass bearings. Steady bearing = collision risk. |
| Rule 8 | Action to Avoid Collision | Action must be positive, made in ample time, large enough to be readily apparent to the other vessel. Sequence of small alterations is dangerous. Avoid creating a close-quarters situation. | Action must be: early, large, and obvious. Small changes are prohibited. |
| Rule 9 | Narrow Channels | Keep to the starboard side. Vessels <20m or sailing vessels must not impede channel vessels. No crossing if it impedes. No anchoring except emergency. | 'Shall not impede' vs. 'shall not cross' — know the difference. Overtaking signals required. |
| Rule 10 | Traffic Separation Schemes | Proceed in the lane, in the general direction of traffic flow. Join/leave at termination points or from the side at a small angle. Cross at right angles (or as close as possible). | Crossing a TSS: right angles to direction of traffic flow. Vessels <20m must not impede. |
| Rule 13 | Overtaking | Approaching from >22.5° abaft the beam = overtaking. Give-way vessel regardless of type. Remains give-way until past and clear. | Overtaking supersedes all other rules including Rule 18 pecking order. |
| Rule 14 | Head-On Situation | Nearly reciprocal courses, risk of collision — both vessels alter to starboard. No stand-on vessel. When in doubt, assume head-on. | Indicators: masthead lights in vertical line, or both red and green sidelights visible. |
| Rule 15 | Crossing Situation | Other vessel on your starboard = you give way. See red light = give way. See green light = stand on. Give-way vessel should avoid crossing ahead. | Red = give way. Green = stand on. Give-way should NOT cross ahead of stand-on. |
| Rule 16 | Give-Way Vessel | Take early and substantial action to keep well clear. Action must be apparent and effective. Avoid crossing ahead of stand-on. | 'Early and substantial' — small alterations do not satisfy Rule 16. |
| Rule 17 | Stand-On Vessel | Maintain course and speed. May maneuver when give-way fails to act. Must maneuver when collision cannot otherwise be avoided. Must not turn to port for vessel on own port side. | Stand-on: maintain, may act, must act — three tiers. No port turn for port-side vessel. |
| Rule 18 | Responsibilities Between Vessels | Pecking order: NUC > RAM > CBD (COLREGS) > Fishing > Sailing > Power. Overtaking rule always supersedes this order. | CBD is COLREGS only — does not exist in Inland Rules. CBD is the most commonly missed on exams. |
| Rule 19 | Restricted Visibility | Rules 12–18 suspended. Safe speed, engines ready. Radar target forward of beam: don't turn port. Fog signal forward of beam: stop or bare steerageway. | No give-way/stand-on in fog. Radar target forward of beam: avoid turning to port. |
Rule 9 — Narrow Channels: Deep Dive
Core Requirements
- ▸Keep as far to the starboard side of the channel as is safe and practicable
- ▸Vessels <20m and sailing vessels shall not impede vessels that can only navigate in the channel
- ▸Vessels shall not cross a narrow channel if such crossing impedes a vessel constrained to the channel
- ▸No anchoring in a narrow channel except in an emergency
- ▸Vessels engaged in fishing shall not impede the passage of other vessels navigating within a narrow channel
"Shall Not Impede" vs. "Give Way"
These are different obligations. "Give way" means you must take action when a close-quarters situation develops. "Shall not impede" means you must avoid creating that situation in the first place.
A small vessel "shall not impede" a deep-draft vessel in a narrow channel — meaning it must stay clear at all times, not just when a collision is imminent.
Overtaking Signals in Narrow Channels
International COLREGS. Inland Rules use the same signals for all passing agreements (not just overtaking).
Bend Signal — Rule 9(f)
A vessel approaching a bend or area where other vessels may be obscured must sound one prolonged blast. Any approaching vessel that hears it must reply with one prolonged blast. Then both vessels proceed with caution.
This applies whether or not another vessel is heard — sound it at every blind bend in a narrow channel.
Rule 10 — Traffic Separation Schemes
Operating IN a TSS Lane
- ▸Proceed in the appropriate lane in the general direction of traffic flow
- ▸Join or leave at the termination points, or from the side at a small angle
- ▸Keep clear of the separation zone — no entering the zone unless necessary
- ▸Vessels <20m, sailing vessels, and fishing vessels must not impede power-driven vessels in the lane
Crossing a TSS
- ▸Cross at right angles (or as close to right angles as practicable) to the traffic flow
- ▸This means your heading should be 90° to the direction traffic flows in the lanes
- ▸Crossing vessels must give way to vessels in the lane
- ▸Fishing vessels may fish in a separation zone but must not impede lane traffic
Exam Trap: Crossing Angle
The exam often asks "at what angle must a vessel cross a TSS?" The answer is right angles (90°) to the direction of traffic flow — not to the lane boundaries. This distinction matters when lanes are angled.
Rule 17 — Stand-On Vessel: The Three-Tier Decision Chain
Rule 17 is among the most nuanced rules on the exam. It creates a progression of obligations that depend on how the situation develops. Know all three tiers and when each applies.
MUST maintain course and speed
Triggered when: Initial situation — give-way vessel has been identified
The stand-on vessel must hold its course and speed to allow the give-way vessel to determine what action the stand-on will take. Altering early confuses the give-way vessel.
MAY take action to avoid collision
Triggered when: Give-way vessel is not acting appropriately
When it becomes apparent the give-way vessel is not taking proper action, the stand-on vessel may maneuver — by its own action alone. This is permissive, not yet required. The stand-on must NEVER turn to port for a vessel on its own port side.
MUST take action to avoid collision
Triggered when: Collision cannot be avoided by give-way vessel alone
When it is no longer possible for the give-way vessel alone to avoid collision, the stand-on vessel is required to take action — whatever is necessary to avoid a collision. At this point, both vessels share responsibility.
Critical: No Port Turn for Port-Side Vessel
Rule 17(c) explicitly states: the stand-on vessel shall not alter course to port for a vessel on its own port side. In a crossing situation where you are stand-on, if you must maneuver, turn to starboard or reduce speed. Never turn left.
Rule 12 — Sailing Vessels Meeting Each Other
When two sailing vessels encounter each other, Rule 12 — not Rule 15 — applies. Rule 15 (crossing) is for power-driven vessels. Sailing vessel right-of-way follows these three tests in order.
Different tacks
Vessel on the PORT tack gives way to vessel on the STARBOARD tack
Starboard tack = wind comes over your right side. Port tack = wind over your left. Starboard tack wins.
Same tack, different positions
The vessel to WINDWARD gives way to the vessel to LEEWARD
Windward vessel (closer to wind) gives way. Leeward vessel stands on.
Port tack, cannot determine windward vessel
If a vessel on the PORT tack cannot determine whether the other vessel is on port or starboard tack, the port-tack vessel gives way
When uncertain, port-tack always gives way.
Exam Tips — What the USCG Actually Tests
The Overtaking Override
Whenever an exam question says a vessel is overtaking, Rule 13 applies and all other rules are secondary. A sailboat overtaking a powerboat is the give-way vessel — this surprises many students.
CBD = COLREGS Only
Constrained by Draft (CBD) exists in the International Regulations (COLREGS) but NOT in U.S. Inland Rules. Exam questions about Inland Rule 18 will not have CBD as an option.
Head-On vs. Crossing — When in Doubt
If you cannot determine whether a situation is head-on or crossing, treat it as head-on and turn to starboard. The exam tests this principle directly.
Rule 19 Suspends 12–18
In restricted visibility, Rules 12–18 (the steering and sailing rules) do NOT apply. There is no stand-on vessel in fog. Both vessels must navigate by Rule 19 alone — know this cold.
Stand-On: Never Turn to Port
The stand-on vessel must never alter course to port for a vessel on its own port side. In a crossing where you are the stand-on, turning right (starboard) is the only safe maneuver.
TSS Crossing Angle
When crossing a Traffic Separation Scheme, you must cross at right angles (or as close to right angles as possible) to the direction of traffic flow — not just any convenient angle.
'Shall Not Impede' vs. 'Give Way'
Rule 9 says small vessels 'shall not impede' vessels constrained to the channel — this is a different, higher burden than 'give way.' It means avoid creating any encounter that might require the other vessel to maneuver at all.
Steady Bearing = Collision
The definitive test for collision risk: take a series of compass bearings on the approaching vessel. If the bearing is steady and range is decreasing, a collision will occur unless action is taken.
Frequently Asked Questions
What is the COLREGS 'pecking order' and how is it tested on the USCG exam?
Rule 18 establishes which vessel has the right of way when two vessels meet. From highest priority (most burdened) to lowest: a vessel not under command (NUC) has the highest right of way; then restricted in ability to maneuver (RAM); then constrained by draft (inland/international waters differ — CBDis a COLREGS-only category); then a vessel engaged in fishing (with gear deployed); then a sailing vessel under sail alone; then a power-driven vessel underway. A power-driven vessel must give way to all of the above. When in doubt, the vessel lower on the list gives way. Exception: Rule 13 overtaking supersedes all — an overtaking vessel is always the give-way vessel regardless of type.
How do you determine if a vessel is overtaking under Rule 13?
A vessel is overtaking if it is approaching another vessel from more than 22.5° abaft the beam — that is, from a bearing more than 22.5° behind the other vessel's midship line. In practice: if you can see only the stern light (white) of the vessel ahead, you are in the overtaking arc and are the give-way vessel. The overtaking rule overrides all other steering and sailing rules — even a sailing vessel overtaking a power-driven vessel must give way. Any doubt about whether you are overtaking means you must assume you are.
What are the duties of the give-way vessel under Rule 16?
The give-way vessel must take early and substantial action to keep well clear. 'Early' means acting in time for the stand-on vessel to see and understand your action. 'Substantial' means a course or speed change large enough to be apparent to the other vessel — a 5° course change does not count. The give-way vessel should, if possible, avoid crossing ahead of the stand-on vessel. Actions must be positive: a large alteration of course, a significant reduction of speed, or both. Hesitating and waiting for the other vessel to react is a violation of Rule 16.
What can the stand-on vessel do under Rule 17 if the give-way vessel is not acting?
Rule 17 has three tiers. First, the stand-on vessel must maintain course and speed. Second, when it becomes apparent the give-way vessel is not acting, the stand-on vessel may (permissive) take action to avoid collision by maneuver alone. Third, when collision cannot be avoided by the give-way vessel alone, the stand-on vessel must (mandatory) take action. The stand-on vessel must never turn to port for a vessel on its own port side (in a crossing situation). The five short blasts danger signal should be sounded any time doubt arises. Early action is always better than waiting until the last moment.
What is a head-on situation under Rule 14 and what is the required action?
A head-on situation exists when two power-driven vessels meet on nearly reciprocal courses so as to involve risk of collision. Indicators: you see both the masthead lights of the other vessel in a vertical line, or nearly so, and/or both sidelights. Both vessels must alter course to starboard (turn right) so that each vessel passes on the port side of the other. There is no stand-on/give-way in a head-on — both vessels share equal obligation to turn right. When doubt exists, assume the situation is head-on and alter to starboard.
How does Rule 15 define a crossing situation, and which vessel gives way?
A crossing situation exists when two power-driven vessels are on intersecting courses and there is risk of collision, and the situation is neither head-on nor overtaking. The vessel that has the other on its own starboard side is the give-way vessel and must keep out of the way. The stand-on vessel is to port of the give-way vessel. Memory aid: if you see a red light (port sidelight) of the approaching vessel, you are the give-way vessel — red means stop, give way. If you see a green light (starboard) on the approaching vessel, you are the stand-on vessel.
What are the key rules for navigating narrow channels under Rule 9?
Rule 9 requires: (1) vessels must keep as far to the starboard side of the channel as safe and practicable; (2) vessels less than 20 meters or sailing vessels must not impede the passage of a vessel that can navigate safely only within a narrow channel — this is the 'shall not impede' duty; (3) vessels shall not cross a narrow channel if such crossing impedes a vessel that can only navigate in the channel; (4) overtaking in a narrow channel requires a signal exchange (in international waters: one prolonged + one short to overtake on starboard side of overtaken vessel, one prolonged + two short to overtake on port side); (5) vessels shall not anchor in a narrow channel except in an emergency.
What does Rule 19 require in restricted visibility, and how is it different from clear weather rules?
Rule 19 applies when vessels are not in sight of one another in or near restricted visibility. Key requirements: (1) every vessel must proceed at a safe speed adapted to the existing circumstances of restricted visibility; (2) power-driven vessels must have engines ready for immediate maneuver; (3) if you detect a vessel forward of the beam by radar alone, you must avoid altering course to port (for a vessel other than overtaking); (4) if you hear a fog signal forward of the beam, you must reduce speed to bare steerageway or stop; (5) the steering and sailing rules (Rules 12–18) do NOT apply — you cannot 'stand on' in fog. Both vessels have equal obligation to navigate safely.
What factors determine 'safe speed' under Rule 6?
Rule 6 does not set a specific speed — it requires every vessel to proceed at a safe speed so that proper and effective action can be taken to avoid collision. Factors include: visibility, traffic density, maneuverability of the vessel (stopping distance and turning ability), background light at night, state of wind/sea/current, proximity of hazards, and the vessel's draft relative to available water depth. For radar-equipped vessels: radar range scale in use, radar detection limits, and the number, location, and movement of targets detected. Safe speed is not just slow — at zero traffic in good visibility, a higher speed may be perfectly safe.
What is a Traffic Separation Scheme (TSS) and what does Rule 10 require?
A Traffic Separation Scheme (TSS) is a routing measure that separates opposing streams of traffic by a separation zone or line. Rule 10 requires: (1) vessels must proceed in the appropriate traffic lane in the general direction of traffic flow; (2) vessels must join or leave a TSS at the termination points, or if joining from the side, at as small an angle as practicable; (3) vessels not using the TSS must keep clear of the separation zone by as wide a margin as practicable; (4) vessels under 20 meters, sailing vessels, and fishing vessels must not impede power-driven vessels in the lane; (5) vessels engaged in fishing may fish within a separation zone but must not impede lane traffic; (6) crossing the TSS must be done at right angles or as nearly right angles as practicable to the general direction of traffic flow.
What constitutes 'risk of collision' under Rule 7, and how must it be determined?
Rule 7 requires every vessel to use all available means to determine whether risk of collision exists. The primary tool is compass bearing: take a series of compass bearings on the approaching vessel — if the bearing does not change (steady bearing, decreasing range), risk of collision exists. Even a slightly changing bearing may indicate collision risk with a large vessel or at close range. Radar must be used properly — not just switched on but actively plotting or tracking targets. Scanty information (e.g., only a few radar returns) must not be assumed to mean no risk. When in doubt, risk of collision must be assumed to exist.
Related Study Guides
Navigation Lights
Masthead, sidelight, stern light arcs, and vessel type light configurations for the USCG exam.
Sound & Light Signals
Whistle signals, danger signals, fog signals, and maneuvering signal rules — COLREGS and Inland.
Man Overboard Procedures
Williamson Turn, Anderson Turn, VHF Pan-Pan, hypothermia tables, and victim recovery.
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