Prepare for Chief Mate and deck officer oral examinations with short answers to International COLREG Rules 1–19. Start with the rule, explain the duty, then describe how you would assess and monitor the situation.
Quick answer: how should I approach a COLREG oral question?
- Establish visibility and visual contact. Are the vessels in sight of one another? Are you in or near restricted visibility?
- Identify the vessels and setting. Consider vessel status, a narrow channel, a traffic separation scheme and any overtaking situation.
- Assess collision risk. Use all appropriate available means; one bearing or an AIS label is not enough.
- State the applicable duty and action. Explain who must do what, and any qualifications.
- Check the result. Continue observing until the other vessel is finally past and clear.
These are practice questions and model answers, written for revision. Read them alongside the full International Rules; the short answers do not reproduce every provision.
Which COLREG rules apply?
| Rules | Application |
|---|---|
| 1–3 | General application, responsibility and definitions. |
| 4–10 | Conduct of vessels in any condition of visibility. |
| 11–18 | Conduct of vessels in sight of one another. This means visual observation. |
| 19 | Vessels not in sight of one another when navigating in or near an area of restricted visibility. Rules 4–10 still apply. |
Oral trap: detecting a vessel by radar or AIS does not make the vessels “in sight.” Darkness alone is not restricted visibility.
Reference: official navigation rules, Rules 3, 4, 11 and 19. The linked publication includes both International and US Inland text; use the International provisions for this guide.
Rules 1–3: general rules and definitions
Rule 1 — Application
Where do the International COLREGs apply?
To all vessels on the high seas and in connected waters navigable by seagoing vessels.
Can there be local rules?
Yes. Appropriate authorities may make special rules for places such as harbours, roadsteads, rivers and inland waterways. Those rules must conform as closely as possible to COLREGs.
Follow-up: warships and special-purpose vessels are not generally exempt. Rule 1 permits specified additional signals for warships, convoys and fishing fleets. Where a special-purpose vessel cannot fully meet specified light, shape or sound-signal requirements, government-approved alternatives must achieve the closest possible compliance.
Rule 2 — Responsibility
Does following one rule automatically remove responsibility?
No. The vessel, owner, master and crew remain responsible for neglect of the Rules and of precautions required by ordinary seamanship or the circumstances.
When may departure from the Rules be necessary?
When special circumstances, including the limitations of the vessels involved, make departure necessary to avoid immediate danger. Rule 2 is not permission to depart merely for convenience.
Follow-up: calling the master does not suspend the officer of the watch’s duty to take necessary action.
Rule 3 — General definitions
Which definitions must I distinguish clearly?
| Term | Oral answer |
|---|---|
| Power-driven vessel | A vessel propelled by machinery. |
| Sailing vessel | A vessel under sail, with any fitted propulsion machinery not being used. |
| Engaged in fishing | Fishing with apparatus that restricts manoeuvrability. Trolling lines or other gear that does not restrict manoeuvrability do not qualify. |
| NUC | Not under command: an exceptional circumstance prevents the vessel from manoeuvring as the Rules require, so she cannot keep out of another vessel’s way. |
| RAM | Restricted in ability to manoeuvre: the nature of her work restricts manoeuvring as required by the Rules, so she cannot keep out of another vessel’s way. |
| CBD | Constrained by draught: a power-driven vessel severely restricted in deviating from her course because of draught in relation to available depth and width of navigable water. |
| Underway | Neither at anchor, nor made fast to the shore, nor aground. |
| In sight | One vessel can be observed visually from the other. |
| Restricted visibility | Visibility restricted by fog, mist, falling snow, heavy rainstorms, sandstorms or similar causes. |
Is underway the same as making way?
No. Making way refers to movement through the water. A vessel can be underway without making way. Stopping engines does not automatically make a vessel NUC.
Give examples of RAM work.
Servicing navigation marks or submarine cables/pipelines; dredging, surveying or underwater work; replenishment or transfers while underway; launching or recovering aircraft; mineclearance; and towing that severely restricts the towing vessel and tow in deviating from their course. The list is not exhaustive.
Other definitions to revise: “vessel” includes non-displacement craft, WIG craft and seaplanes used or capable of use as transport on water. Length means length overall; breadth means greatest breadth. A seaplane is an aircraft designed to manoeuvre on water; WIG craft use surface-effect action close to the surface.
Source: International Rules 1–3.
Rules 4–10: conduct in any visibility
Rule 4 — Application
Do Rules 5–10 stop applying in fog?
No. Rule 4 makes this section applicable in any condition of visibility. Look-out, safe speed, collision-risk assessment and the other duties continue when Rule 19 applies.
Rule 5 — Look-out
What is a proper look-out?
Every vessel must maintain one at all times, using sight, hearing and all available means appropriate to the conditions, to fully assess the situation and collision risk.
Follow-up: radar and AIS support the look-out; they do not replace looking and listening. A vessel at anchor is also subject to Rule 5.
Rule 6 — Safe speed
What makes a speed safe?
It must allow proper and effective collision-avoidance action and stopping within a distance appropriate to the conditions.
What factors apply to all vessels?
- Visibility.
- Traffic density, including fishing vessels and other concentrations.
- Manoeuvrability, especially stopping distance and turning ability.
- At night, background lighting and backscatter from the vessel’s own lights.
- Wind, sea, current and nearby navigational hazards.
- Draught relative to available water depth.
What additional factors apply with operational radar?
- The radar’s characteristics, efficiency and limitations.
- Constraints caused by the selected range scale.
- Effects of sea state, weather and interference.
- Possible failure to detect small vessels, ice or floating objects at adequate range.
- The number, position and movement of detected vessels.
- The more exact assessment of visibility possible from radar ranges of nearby vessels or objects.
Oral trap: the rule sets no universal speed in knots. Good visibility or working radar does not, by itself, justify full speed.
Rule 7 — Risk of collision
How do you determine collision risk?
Use all appropriate available means. If in doubt, assume the risk exists. Use fitted, operational radar properly, including long-range scanning and plotting or equivalent systematic observation.
Does an unchanging bearing prove risk?
An approaching vessel whose compass bearing does not appreciably change must be treated as a collision risk. An appreciable bearing change can still leave risk, especially with a very large vessel, a tow or a vessel at close range.
Follow-up: do not reach conclusions from scanty information. A single radar observation, an unverified AIS prediction or a fixed “safe CPA” number is not a complete assessment.
Rule 8 — Action to avoid collision
What should effective action look like?
It should comply with the steering and sailing rules and, where circumstances allow, be positive, made in ample time and consistent with good seamanship. Course or speed changes should be readily apparent; avoid a succession of small alterations.
Allow safe passing distance and check effectiveness until the other vessel is finally past and clear. Course alteration alone may work if there is sufficient sea room and it creates no other close-quarters situation. If necessary, reduce speed, stop or reverse propulsion.
Does “not impede” mean the same as “keep out of the way”?
No. A not-impede duty requires early action, when needed, to leave sufficient sea room for safe passage. If collision risk develops, that duty continues and the applicable steering and sailing rules must also be considered.
Follow-up: the vessel whose passage must not be impeded still has collision-avoidance obligations. She does not gain permission to stand into danger.
Rule 9 — Narrow channels
Where should a vessel navigate along a narrow channel?
As near the starboard outer limit as is safe and practicable.
- Under 20 m or sailing: must not impede a vessel that can safely navigate only within the channel or fairway.
- Engaged in fishing: must not impede any other vessel navigating within it.
- Crossing: must not impede a vessel that can safely navigate only within it.
What if an overtaken vessel must help make passing safe?
For vessels in sight, use the intention and agreement signals in Rule 34(c); the overtaken vessel, if agreeing, takes steps to permit safe passing. The overtaking vessel remains responsible under Rule 13.
Follow-up: approach an obscured bend with particular alertness and caution and sound the Rule 34(e) signal. Avoid anchoring in a narrow channel when circumstances allow.
Rule 10 — Traffic separation schemes
Does using a traffic lane give automatic priority?
No. Rule 10 applies to IMO-adopted schemes and does not remove duties under other rules.
- Proceed in the lane’s general traffic-flow direction and keep clear of separation lines or zones as far as practicable.
- Normally join or leave at the lane’s end. When joining or leaving from the side, use as small an angle to traffic flow as practicable.
- Avoid crossing lanes where practicable. If obliged to cross, use a heading as close as practicable to a right angle to traffic flow.
- Use particular caution near terminations. Avoid anchoring in the scheme or near its ends as far as practicable; non-users should keep as far clear as practicable.
Who may use an inshore traffic zone?
Vessels under 20 m, sailing vessels and vessels engaged in fishing may use it. Other vessels should not use it when they can safely use the adjacent lane, but may do so for destinations within the zone, including ports and pilot stations, or to avoid immediate danger.
Can vessels enter the separation zone?
A vessel not crossing, joining or leaving a lane should normally stay out, except in an emergency to avoid immediate danger or to fish within the separation zone.
What are the not-impede duties?
Fishing vessels must not impede any vessel following a lane. Sailing vessels and vessels under 20 m must not impede a power-driven vessel’s safe passage along a lane.
Follow-up: the right-angle requirement concerns heading, not course over ground. Specific RAM exemptions for maintaining navigation safety or working on submarine cables within a scheme extend only as far as necessary for the operation.
Source: International Rules 4–10. Rules 34 and 35 contain the detailed sound-signal requirements and should be revised alongside this page.
Rules 11–18: vessels in sight of one another
Rule 11 — Application
When do Rules 12–18 apply?
When vessels are in sight of one another. A radar target alone is not visual contact. If vessels are not in sight while navigating in or near restricted visibility, assess the encounter under Rule 19, together with Rules 4–10.
Rule 12 — Sailing vessels
Two sailing vessels approach with collision risk. Who keeps out of the way?
- Wind on different sides: the vessel with wind on her port side.
- Wind on the same side: the windward vessel keeps out of the leeward vessel’s way.
- Port-side wind and uncertain: if a vessel sees another to windward and cannot determine which side the other has the wind on, she keeps out of the way.
Follow-up: windward is the side opposite the mainsail; for a square-rigged vessel, use the largest fore-and-aft sail. Check Rule 13 first if one vessel is overtaking. A vessel using propulsion machinery is not a sailing vessel under Rule 3.
Rule 13 — Overtaking
How do you recognise overtaking?
You are coming up from more than 22.5° abaft the other vessel’s beam: at night, a position from which you would see her sternlight but neither sidelight.
Who keeps out of the way?
Any vessel overtaking another. This obligation applies notwithstanding the other rules in Sections I and II. If in doubt about being the overtaking vessel, assume you are.
Follow-up: your duty continues until finally past and clear. A later bearing change does not turn you into a crossing vessel or relieve the duty. A sailing vessel overtaking a power-driven vessel must keep out of the way.
Rule 14 — Head-on situation
What is required in a head-on situation?
When two power-driven vessels meet on reciprocal or nearly reciprocal courses with collision risk, each alters to starboard so they pass port side to port side.
How is it recognised?
The other vessel is ahead or nearly ahead. At night, the masthead lights appear in or nearly in line and/or both sidelights are visible; by day, the corresponding aspect is seen. If in doubt, assume the situation exists.
Oral trap: Rule 14 is a rule for vessels in sight. A radar-only target ahead in fog must be assessed under Rule 19.
Rule 15 — Crossing situation
Two power-driven vessels are crossing with collision risk. Who gives way?
The vessel with the other on her starboard side keeps out of the way and, if circumstances allow, avoids crossing ahead.
Follow-up: establish that this is a crossing encounter between two power-driven vessels in sight, and check other applicable obligations. One sighting on the starboard bow is not enough to prescribe a helm order without assessing risk, sea room and other traffic.
Rule 16 — Action by the give-way vessel
How should the give-way vessel act?
As far as possible, take early and substantial action to keep well clear. Choose an effective manoeuvre consistent with the applicable rules, then monitor its result.
Follow-up: a series of small course changes may be difficult for the other vessel to recognise and conflicts with the guidance in Rule 8.
Rule 17 — Action by the stand-on vessel
Must the stand-on vessel always maintain course and speed?
No. Explain the changing duties in three stages:
| Stage | Stand-on duty |
|---|---|
| Initially — 17(a)(i) | Maintain course and speed. |
| May act — 17(a)(ii) | May take avoiding action by her own manoeuvre alone as soon as it becomes apparent that the give-way vessel is not taking appropriate action. |
| Must act — 17(b) | When so close that the give-way vessel’s action alone cannot avoid collision, take the action that will best help avoid it. |
Can the stand-on vessel alter to port?
In a crossing situation between power-driven vessels, a stand-on vessel acting under 17(a)(ii) must, if circumstances allow, avoid altering to port for a vessel on her own port side.
Oral trap: this is a qualified provision for that particular situation, not a universal “never turn to port” rule. Action by the stand-on vessel does not remove the give-way vessel’s duty.
Rule 18 — Responsibilities between vessels
How do you explain the responsibilities?
Start with the qualification: except where Rules 9, 10 and 13 otherwise require.
| Vessel | Must keep out of the way of |
|---|---|
| Power-driven, underway | NUC, RAM, vessels engaged in fishing and sailing vessels. |
| Sailing, underway | NUC, RAM and vessels engaged in fishing. |
| Fishing, underway | NUC and RAM, so far as possible. |
Where does a vessel constrained by draught fit?
Every vessel except NUC or RAM must, if circumstances allow, avoid impeding the safe passage of a CBD vessel exhibiting Rule 28 signals. The CBD vessel must navigate with particular caution. This is not an unconditional extra rung in a priority list.
What about seaplanes and WIG craft?
A seaplane on the water should generally stay well clear and avoid impeding vessels; where collision risk exists, it follows Part B. A WIG craft taking off, landing or flying near the surface keeps well clear of other vessels and avoids impeding them. On the water surface, it follows the rules for power-driven vessels.
Follow-up: a pilot vessel has no special Rule 18 priority merely because it is on pilotage duty. A tug is not automatically RAM; the nature and restriction of the towing operation matter.
Source: International Rules 11–18.
Rule 19 — Restricted visibility
When does Rule 19 apply?
To vessels not in sight of one another when navigating in or near an area of restricted visibility.
What are the immediate requirements?
Proceed at a safe speed adapted to the conditions. A power-driven vessel must have her engines ready for immediate manoeuvre. Apply Rules 4–10 with proper regard to the restricted visibility.
What if another vessel is detected by radar alone?
Determine whether a close-quarters situation is developing or collision risk exists. If so, take avoiding action in ample time.
| Target position | Course alteration to avoid |
|---|---|
| Forward of the beam | An alteration to port, except for a vessel being overtaken. |
| Abeam or abaft the beam | An alteration towards the vessel. |
What if you hear a fog signal apparently forward of the beam?
Unless you have determined that collision risk does not exist, reduce speed to the minimum at which you can keep course. If necessary, take all way off and navigate with extreme caution until the danger is over.
The same requirement applies when you cannot avoid a close-quarters situation with another vessel forward of the beam.
Oral trap: Rule 19 does not assign a stand-on/give-way pair as the in-sight crossing rule does. Both vessels must assess and act as required. Other applicable duties, including narrow-channel and TSS not-impede obligations, continue.
References: International Rule 19 and MCA guidance on navigation in restricted visibility.
Oral practice: say your answer, then check
These original practice situations test the distinctions above. State your assumptions; the examiner may change the visibility, vessel status or sea room.
1. A sailing yacht is overtaking your power-driven vessel. Who keeps clear? Reveal answer
The yacht keeps out of the way under Rule 13. The usual power-driven/sailing relationship does not displace the overtaking duty. Confirm that the vessels are in sight and the encounter meets the overtaking definition.
2. Your engines are stopped while drifting. Are you NUC? Reveal answer
Not automatically. You are underway if not anchored, made fast to shore or aground. NUC requires an exceptional circumstance that prevents manoeuvring as the Rules require. Describe any actual failure and its effect; stopped engines alone do not establish NUC.
3. In a power-driven crossing encounter, the vessel on your port side is not giving way. What changes? Reveal answer
Explain Rule 17’s stages: initially maintain course and speed; you may act when its failure to take appropriate action becomes apparent; you must act when its action alone can no longer avoid collision. Apply the qualified restriction on a port alteration under 17(a)(ii). Monitor continuously rather than waiting for a fixed distance.
4. In fog, a radar-only target on your starboard bow has a steady bearing and decreasing range. Are you the give-way vessel under Rule 15? Reveal answer
No. With the vessels not in sight in restricted visibility, use Rule 19 and Rules 4–10. Assess the developing encounter systematically and take avoiding action in ample time. If altering course, avoid port for a target forward of the beam so far as possible, except when overtaking it. Select action that also accounts for other traffic and sea room.
5. A fog signal is heard ahead, but radar shows no target. Can you maintain speed? Reveal answer
Radar non-detection does not establish absence of risk. Unless collision risk has been ruled out, Rule 19(e) requires reduction to minimum course-keeping speed, taking all way off if necessary, and extreme caution until the danger is over. Maintain the proper look-out and investigate the signal.
6. Current is setting you along a traffic lane while you cross it. Must your track be 90° to the lane? Reveal answer
Rule 10 specifies a heading as nearly as practicable at right angles to traffic flow, not a ground track of exactly 90°. First consider whether crossing is necessary, then assess traffic and other applicable rules.
7. A small sailing vessel wants to cross ahead of a ship confined to a narrow channel. Does sail give priority? Reveal answer
No. Rule 9 requires the sailing vessel not to impede the ship that can safely navigate only within the channel; the crossing provision also applies. Take early action to leave sufficient sea room. If collision risk nevertheless develops, both vessels must fulfil the applicable collision-avoidance duties.
8. Another vessel suggests a different passing arrangement on VHF. Is agreement enough? Reveal answer
No. Positively identifying the caller can be difficult, and misunderstandings or delayed action can create danger. Communication does not replace COLREG compliance. Assess the encounter, act under the applicable rules and use the required signals. Treat AIS as supporting information rather than the sole basis for avoidance.
Communication reference: MCA MGN 324 Amendment 2: VHF and AIS use.
A simple oral revision routine
- Name the rule and when it applies. Say whether visual contact, restricted visibility or a particular vessel type is required.
- Give the main duty in one or two sentences. Then add the important qualification.
- Answer one changed situation. For example: what if the other vessel is overtaking, or disappears into fog?
- Finish with assessment and monitoring. Explain how you will check that the action is working.
Revise the exact statutory wording alongside these explanations, especially the differences between shall, may, if circumstances admit and so far as possible. Continue with lights, shapes and sound signals in Rules 20–37 for broader oral preparation.
Official reading: IMO overview of the COLREG Convention and full navigation rules — read the International provisions.
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