Part B: Steering and Sailing Rules (Rules 4 to 19)
Part B is the working core of the instrument and divides into three sections. Section I (Rules 4 to 10) binds in any condition of visibility. Section II (Rules 11 to 18) binds only when vessels are in sight of one another. Section III (Rule 19) governs vessels not in sight of one another in or near restricted visibility. Which section is live is decided by the visibility state first of all (Chapter 5; Chapter 8).
Section I: Conduct of Vessels in Any Condition of Visibility (Rules 4 to 10)
Rule 4: Application
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Rules in this Section apply in any condition of visibility.
ANNOTATION
A one-line gate. Section I applies “in any condition of visibility,” which is what makes the look-out, safe speed, risk-of-collision and avoiding-action Rules universal: they bind in clear weather and in fog alike, before the question of whether you can see the other vessel is even reached. See Chapter 5; Chapter 8.
Rule 5: Look-out
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Every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision.
ANNOTATION
The shortest of the major Rules and among the most cited in court. Every vessel keeps a proper look-out “at all times,” the continuous-duty marker (it is owed whether or not a contact is present), “by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions.” Note the word “in”: Rule 5 reads “appropriate in,” where Rule 7(a) reads “appropriate to.” The purpose clause is the test of adequacy: the look-out must be enough “to make a full appraisal of the situation and of the risk of collision.” All available means reaches beyond eyes and ears to radar, AIS and VHF where carried (Cockcroft & Lameijer, 7th ed, comment on Rule 5). See Chapter 7; Rule 7; at all times in the Glossary.
Rule 6: Safe Speed
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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 and conditions. In determining a safe speed the following factors shall be among those taken into account:
(a) By all vessels:
(i) the state of visibility;
(ii) the traffic density including concentrations of fishing vessels or any other vessels;
(iii) the manoeuvrability of the vessel with special reference to stopping distance and turning ability in the prevailing conditions;
(iv) at night the presence of background light such as from shore lights or from back scatter of her own lights;
(v) the state of wind, sea and current, and the proximity of navigational hazards;
(vi) the draught in relation to the available depth of water.
(b) Additionally, by vessels with operational radar:
(i) the characteristics, efficiency and limitations of the radar equipment;
(ii) any constraints imposed by the radar range scale in use;
(iii) the effect on radar detection of the sea state, weather and other sources of interference;
(iv) the possibility that small vessels, ice and other floating objects may not be detected by radar at an adequate range;
(v) the number, location and movement of vessels detected by radar;
(vi) the more exact assessment of the visibility that may be possible when radar is used to determine the range of vessels or other objects in the vicinity.
ANNOTATION
Every vessel proceeds at a safe speed “at all times,” the second continuous duty. Safe speed is defined by what it must allow, not by a number: speed such “that she can take proper and effective action to avoid collision and be stopped within a distance appropriate to the prevailing circumstances and conditions.” The list at (a) sets the factors all vessels weigh (visibility; traffic density; manoeuvrability, especially stopping distance and turning ability; at night the presence of background light such as shore lights or backscatter; the state of wind, sea and current; and draught in relation to depth). The list at (b) adds factors for vessels with operational radar (its characteristics and limitations, the constraints of the range scale in use, the effect of sea state and weather on detection, the possibility that small craft and ice go undetected, the number and movement of contacts, and the more exact assessment of visibility radar can give). The Rule never fixes a figure because the safe speed is the one the circumstances allow, which is why the factor list is best read as a table. See Chapter 7; safe speed in the Glossary.
Rule 7: Risk of Collision
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(a) Every vessel shall use all available means appropriate to the prevailing circumstances and conditions to determine if risk of collision exists. If there is any doubt such risk shall be deemed to exist.
(b) Proper use shall be made of radar equipment if fitted and operational, including long-range scanning to obtain early warning of risk of collision and radar plotting or equivalent systematic observation of detected objects.
(c) Assumptions shall not be made on the basis of scanty information, especially scanty radar information.
(d) In determining if risk of collision exists the following considerations shall be among those taken into account:
(i) such risk shall be deemed to exist if the compass bearing of an approaching vessel does not appreciably change;
(ii) such risk may sometimes exist even when an appreciable bearing change is evident, particularly when approaching a very large vessel or a tow or when approaching a vessel at close range.
ANNOTATION
(a) The duty and the doubt rule. Every vessel uses “all available means appropriate to the prevailing circumstances and conditions” to determine if risk of collision exists. The qualifier is “to” here, against the “in” of Rule 5; the wording differs and the guide flags this as a point for discussion rather than asserting a settled legal gap (Chapter 6). The key instruction is the doubt rule: “if there is any doubt such risk shall be deemed to exist.” Doubt is resolved conservatively, by assuming the risk. See Chapter 6; Chapter 8.
(b) Radar. Proper use is required of radar “if fitted and operational,” including long-range scanning to get early warning, and radar plotting or equivalent systematic observation. The duty is to use the equipment you have, properly. See Rule 6(b).
(c) Scanty information. “Assumptions shall not be made on the basis of scanty information, especially scanty radar information.” A caution against acting on a contact you have not properly resolved. See Chapter 8.
(d) Determining whether risk exists. Two tests. Under (d)(i) risk “shall be deemed to exist” if the compass bearing of an approaching vessel “does not appreciably change,” the constant-bearing test, again phrased as a deeming so it is not a matter of opinion. Under (d)(ii) risk “may sometimes exist” even with an appreciable bearing change, “particularly when approaching a very large vessel or a tow or when approaching a vessel at close range,” which closes the obvious loophole. See Chapter 8; risk of collision in the Glossary.
Rule 8: Action to Avoid Collision
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(a) Any action to avoid collision shall be taken in accordance with the Rules of this Part and shall, if the circumstances of the case admit, be positive, made in ample time and with due regard to the observance of good seamanship.
(b) Any alteration of course and/or speed to avoid collision shall, if the circumstances of the case admit, be large enough to be readily apparent to another vessel observing visually or by radar; a succession of small alterations of course and/or speed should be avoided.
(c) If there is sufficient sea room, alteration of course alone may be the most effective action to avoid a close-quarters situation provided that it is made in good time, is substantial and does not result in another close-quarters situation.
(d) Action taken to avoid collision with another vessel shall be such as to result in passing at a safe distance. The effectiveness of the action shall be carefully checked until the other vessel is finally past and clear.
(e) If necessary to avoid collision or allow more time to assess the situation, a vessel shall slacken her speed or take all way off by stopping or reversing her means of propulsion.
(f)
(i) A vessel which, by any of these Rules, is required not to impede the passage or safe passage of another vessel shall, when required by the circumstances of the case, take early action to allow sufficient sea room for the safe passage of the other vessel.
(ii) A vessel required not to impede the passage or safe passage of another vessel is not relieved of this obligation if approaching the other vessel so as to involve risk of collision and shall, when taking action, have full regard to the action which may be required by the Rules of this part.
(iii) A vessel the passage of which is not to be impeded remains fully obliged to comply with the Rules of this part when the two vessels are approaching one another so as to involve risk of collision.
ANNOTATION
(a) Ample time and good seamanship. Any avoiding action is “positive, made in ample time and with due regard to the observance of good seamanship.” Ample time is the standard for being early enough to be effective without becoming an emergency (Cockcroft & Lameijer, 7th ed, comment on Rule 8). See Chapter 8; ample time in the Glossary.
(b) Readily apparent. Any alteration of course or speed “shall be large enough to be readily apparent to another vessel observing visually or by radar; a succession of small alterations should be avoided.” The point is to make your action unmistakable, both to the eye and on another ship’s screen. See Chapter 8.
(c) Alteration of course alone. Where there is sea room, a substantial alteration of course alone “may be the most effective action” to avoid a close-quarters situation, provided it is “made in good time,” is substantial, and “does not result in another close-quarters situation.” Note “good time” here against “ample time” at (a); they read as near-synonyms, with ample the stronger (Chapter 6). See Chapter 6; Chapter 8; good time in the Glossary.
(d) Safe distance and checking. Action to avoid collision shall be such as to result in “passing at a safe distance,” and its effectiveness “shall be carefully checked until the other vessel is finally past and clear.” Two undefined but important phrases: safe distance (size, speed and interaction dependent) and finally past and clear (judgeable only in hindsight, the same phrase Rule 13(d) uses to keep an overtaking vessel burdened). See Chapter 8; Chapter 9; safe distance and finally past and clear in the Glossary.
(e) Slackening and stopping. A vessel may “slacken her speed or take all way off by stopping or reversing her means of propulsion.” This is the textual authority for speed, not just course, as avoiding action. To “take all way off” is to stop in the water. See way in the Glossary.
(f) The not-impede paragraphs. Added to fix the meaning of “not to impede” in Rules 9 and 10 (Cockcroft & Lameijer, 7th ed, comment on Rule 8(f); adopted 1987). Read the three together. Under (f)(i) a vessel required not to impede another “shall, when required by the circumstances of the case, take early action to allow sufficient sea room.” Under (f)(ii) the not-impede obligation “is not relieved” by the requirement even if risk of collision develops; the phrase “is not relieved” preserves the duty rather than displacing it. Under (f)(iii) the vessel whose passage is not to be impeded “remains fully obliged to comply” with the Rules of the Part if risk of collision develops. The combined effect is the central lesson of Chapter 8: not to be impeded was never right of way, and once risk of collision exists both vessels are burdened. See Chapter 8; Figure 8-2; not impede in the Glossary.
Rule 9: Narrow Channels
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(a) A vessel proceeding along the course of a narrow channel or fairway shall keep as near to the outer limit of the channel or fairway which lies on her starboard side as is safe and practicable.
(b) A vessel of less than 20 metres in length or a sailing vessel shall not impede the passage of a vessel which can safely navigate only within a narrow channel or fairway.
(c) A vessel engaged in fishing shall not impede the passage of any other vessel navigating within a narrow channel or fairway.
(d) A vessel shall not cross a narrow channel or fairway if such crossing impedes the passage of a vessel which can safely navigate only within such channel or fairway. The latter vessel may use the sound signal prescribed in Rule 34(d) if in doubt as to the intention of the crossing vessel.
(e)
(i) In a narrow channel or fairway when overtaking can take place only if the vessel to be overtaken has to take action to permit safe passing, the vessel intending to overtake shall indicate her intention by sounding the appropriate signal prescribed in Rule 34(c)(i). The vessel to be overtaken shall, if in agreement, sound the appropriate signal prescribed in Rule 34(c)(ii) and take steps to permit safe passing. If in doubt she may sound the signals prescribed in Rule 34(d).
(ii) This Rule does not relieve the overtaking vessel of her obligation under Rule 13.
(f) A vessel nearing a bend or an area of a narrow channel or fairway where other vessels may be obscured by an intervening obstruction shall navigate with particular alertness and caution and shall sound the appropriate signal prescribed in Rule 34(e).
(g) Any vessel shall, if the circumstances of the case admit, avoid anchoring in a narrow channel.
ANNOTATION
(a) Keep to starboard. A vessel proceeding along a narrow channel or fairway keeps “as near to the outer limit of the channel or fairway which lies on her starboard side as is safe and practicable.” The qualifier “as is safe and practicable” is a compound (safe and practicable), more forgiving than plain “possible.” See Chapter 6; so far as practicable in the Glossary.
(b), (c), (d) The not-impede trio. A vessel “of less than 20 metres in length or a sailing vessel” shall not impede the passage of “a vessel which can safely navigate only within a narrow channel or fairway” (b); a vessel engaged in fishing shall not impede “the passage of any other vessel navigating within a narrow channel or fairway” (c), a wider duty owed to all such traffic, not only to the vessel the channel protects; and a vessel shall not cross a narrow channel or fairway “if such crossing impedes the passage” of a vessel which can safely navigate only within it, with the doubt signal of Rule 34(d) available (d). The recurring phrase is “can safely navigate only within,” which marks the vessel the channel exists to protect. See Rule 8(f); Rule 34(d); not impede in the Glossary.
(e) Overtaking in a channel. Where overtaking can take place only if the overtaken vessel takes action to permit safe passing, (e)(i) sets the whistle signals of Rule 34(c) and the requirement for the overtaken vessel’s agreement; (e)(ii) provides that this “does not relieve the overtaking vessel of her obligation” under Rule 13. The phrase “does not relieve” again preserves the Rule 13 duty. See Rule 13; Rule 34(c).
(f) Bends. A vessel nearing a bend or an area where other vessels may be obscured “shall navigate with particular alertness and caution,” sounding the signal of Rule 34(e). This is the mildest of the caution gradings (against “particular caution” and “extreme caution”). See Rule 34(e); extreme caution in the Glossary.
(g) Anchoring. A vessel “shall avoid anchoring in a narrow channel” if the circumstances admit. See Rule 10(g).
Rule 10: Traffic Separation Schemes
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(a) This Rule applies to traffic separation schemes adopted by the Organisation and does not relieve any vessel of her obligation under any other Rule.
(b) A vessel using a traffic separation scheme shall:
(i) proceed in the appropriate traffic lane in the general direction of traffic flow for that lane;
(ii) so far as practicable keep clear of a traffic separation line or separation zone;
(iii) normally join or leave a traffic lane at the termination of the lane, but when joining or leaving from either side shall do so at as small an angle to the general direction of traffic flow as practicable.
(c) A vessel shall, so far as practicable, avoid crossing traffic lanes but if obliged to do so shall cross on a heading as nearly as practicable at right angles to the general direction of traffic flow.
(d)
(i) A vessel shall not use an inshore traffic zone when she can safely use the appropriate traffic lane within the adjacent traffic separation scheme. However, vessels of less than 20 metres in length, sailing vessels and vessels engaged in fishing may use the inshore traffic zone.
(ii) Notwithstanding subparagraph (d)(i), a vessel may use an inshore traffic zone when en route to and from a port, offshore installation or structure, pilot station or any other place situated within the inshore traffic zone, or to avoid immediate danger.
(e) A vessel other than a crossing vessel or a vessel joining or leaving a lane shall not normally enter a separation zone or cross a separation line except:
(i) in cases of emergency to avoid immediate danger;
(ii) to engage in fishing within a separation zone.
(f) A vessel navigating in areas near the terminations of traffic separation schemes shall do so with particular caution.
(g) A vessel shall so far as practicable avoid anchoring in a traffic separation scheme or in areas near its terminations.
(h) A vessel not using a traffic separation scheme shall avoid it by as wide a margin as is practicable.
(i) A vessel engaged in fishing shall not impede the passage of any vessel following a traffic lane.
(j) A vessel of less than 20 metres in length or a sailing vessel shall not impede the safe passage of a power-driven vessel following a traffic lane.
(k) A vessel restricted in her ability to manoeuvre when engaged in an operation for the maintenance of safety of navigation in a traffic separation scheme is exempted from complying with this Rule to the extent necessary to carry out the operation.
(l) A vessel restricted in her ability to manoeuvre when engaged in an operation for the laying, servicing or picking up of a submarine cable, within a traffic separation scheme, is exempted from complying with this Rule to the extent necessary to carry out the operation.
ANNOTATION
(a) Scope and savings. The Rule applies to schemes “adopted by the Organisation” (the IMO) and “does not relieve any vessel of her obligation under any other Rule.” The savings phrase is the same preserving device seen at 8(f) and 9(e). See Rule 1(d).
(b), (c) Using and crossing a scheme. A vessel using a scheme proceeds “in the appropriate traffic lane in the general direction of traffic flow,” keeps clear of the separation line or zone, and normally joins or leaves at the ends or “at as small an angle to the general direction of traffic flow as practicable” (b). A vessel that must cross a lane does so “as nearly as practicable at right angles to the general direction of traffic flow” (c); the right-angle rule makes the crossing quick and her intention obvious. See traffic separation scheme in the Glossary.
(d) Inshore traffic zone. Through traffic shall not normally use the inshore traffic zone, with stated exceptions (vessels under 20 metres, sailing vessels, fishing vessels, and vessels en route to or from a place within the zone). See inshore traffic zone in the Glossary.
(e), (f), (g) Zones, terminations, anchoring. A vessel normally does not enter a separation zone or cross a separation line except in the permitted cases (e); navigates with “particular caution” near the terminations (f); and avoids anchoring within a scheme or near its ends (g). See Rule 9(g).
(h) Vessels not using a scheme. A vessel not using a scheme “shall avoid it by as wide a margin as is practicable.” See above.
(i), (j) The not-impede pair. A vessel engaged in fishing “shall not impede the passage of any vessel following a traffic lane” (i); a vessel of less than 20 metres or a sailing vessel “shall not impede the safe passage of a power-driven vessel following a traffic lane” (j). Note “passage” at (i) and “safe passage” at (j); the wording differs and the guide treats whether that difference bites as a point for discussion (Chapter 6). See Rule 8(f); Chapter 6; passage in the Glossary.
(k), (l) RAM exemptions. A vessel restricted in her ability to manoeuvre when engaged in maintaining safety of navigation in a scheme (k), or in laying, servicing or picking up a submarine cable (l), is exempted from the Rule to the extent necessary to carry out the operation. See Rule 3(g); Rule 27.
Section II: Conduct of Vessels in Sight of One Another (Rules 11 to 18)
Rule 11: Application
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Rules in this Section apply to vessels in sight of one another.
ANNOTATION
The gate to Section II: these Rules apply “to vessels in sight of one another.” Read with Rule 3(k), in sight means observed visually, so the give-way and stand-on Rules switch on only with visual contact and switch off in fog, where Rule 19 takes over. See Chapter 5; Rule 3(k); Rule 19.
Rule 12: Sailing Vessels
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(a) When two sailing vessels are approaching one another, so as to involve risk of collision, one of them shall keep out of the way of the other as follows:
(i) when each has the wind on a different side, the vessel which has the wind on the port side shall keep out of the way of the other;
(ii) when both have the wind on the same side, the vessel which is to windward shall keep out of the way of the vessel which is to leeward;
(iii) if a vessel with the wind on the port side sees a vessel to windward and cannot determine with certainty whether the other vessel has the wind on the port or on the starboard side, she shall keep out of the way of the other.
(b) For the purposes of this Rule the windward side shall be deemed to be the side opposite to that on which the mainsail is carried or, in the case of a square-rigged vessel, the side opposite to that on which the largest fore-and-aft sail is carried.
ANNOTATION
When two sailing vessels approach so as to involve risk of collision, the duty is set by the wind. Under (a)(i), where each has the wind on a different side, “the vessel which has the wind on the port side shall keep out of the way of the other.” Under (a)(ii), where both have the wind on the same side, “the vessel which is to windward shall keep out of the way of the vessel which is to leeward.” Under (a)(iii), a vessel with the wind on her port side that sees a vessel to windward and “cannot determine with certainty” whether the other has the wind on port or starboard, “shall keep out of the way of the other.” Paragraph (b) fixes the windward side as “the side opposite to that on which the mainsail is carried,” and for a square-rigged vessel the side opposite the largest fore-and-aft sail. The terms to know are windward, leeward and tack. See Chapter 7; windward and fore-and-aft sail in the Glossary.
Rule 13: Overtaking
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(a) Notwithstanding anything contained in the Rules of Part B, Sections I and II, any vessel overtaking any other shall keep out of the way of the vessel being overtaken.
(b) A vessel shall be deemed to be overtaking when coming up with another vessel from a direction more than 22.5 degrees abaft her beam; that is, in such a position with reference to the vessel she is overtaking, that at night she would be able to see only the sternlight of that vessel but neither of her sidelights.
(c) When a vessel is in any doubt as to whether she is overtaking another, she shall assume that this is the case and act accordingly.
(d) Any subsequent alteration of the bearing between the two vessels shall not make the overtaking vessel a crossing vessel within the meaning of these Rules or relieve her of the duty of keeping clear of the overtaken vessel until she is finally past and clear.
ANNOTATION
(a) The override. “Notwithstanding anything contained in the Rules of Part B, Sections I and II, any vessel overtaking any other shall keep out of the way of the vessel being overtaken.” “Notwithstanding” is the strongest override word in the instrument: the overtaking duty beats every other steering Rule, so even a vessel that Rule 18 would normally privilege keeps clear while overtaking. See Chapter 6; notwithstanding in the Glossary.
(b) The deeming and the sector. A vessel “shall be deemed to be overtaking” when coming up with another “from a direction more than 22.5 degrees abaft her beam,” that is, in a position from which at night she would see only the sternlight and neither sidelight. The deeming and the precise angle tie the conduct Rule to the light arcs of Rule 21. See Rule 21; abaft the beam in the Glossary.
(c) Doubt. “When a vessel is in any doubt as to whether she is overtaking another, she shall assume that this is the case and act accordingly.” The same conservative default as the doubt rules in 7(a), 14(c) and elsewhere. See Chapter 6.
(d) The lock. Any subsequent alteration of bearing “shall not make the overtaking vessel a crossing vessel” nor “relieve her of the duty of keeping clear until she is finally past and clear.” The phrase “shall not… relieve” preserves the duty through any change in geometry, which is why an overtake cannot quietly become a crossing. See Chapter 9; finally past and clear in the Glossary.
Rule 14: Head-on Situation
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(a) When two power-driven vessels are meeting on reciprocal or nearly reciprocal courses so as to involve risk of collision each shall alter her course to starboard so that each shall pass on the port side of the other.
(b) Such a situation shall be deemed to exist when a vessel sees the other ahead or nearly ahead and by night she could see the masthead lights of the other in a line or nearly in a line and/or both sidelights and by day she observes the corresponding aspect of the other vessel.
(c) When a vessel is in any doubt as to whether such a situation exists she shall assume that it does exist and act accordingly.
ANNOTATION
(a) The action. When two power-driven vessels meet “on reciprocal or nearly reciprocal courses” so as to involve risk of collision, “each shall alter her course to starboard so that each shall pass on the port side of the other.” Both give way; there is no stand-on vessel in a head-on situation. See Chapter 8; head-on situation in the Glossary.
(b) The deeming. The situation “shall be deemed to exist” when a vessel sees the other ahead or nearly ahead and by night could see the masthead lights “in a line or nearly in a line” and both sidelights, or by day sees the corresponding aspect. The deeming pins the classification to what is actually seen. See Rule 21; Rule 23.
(c) Doubt. “If there is any doubt” whether a head-on situation exists, “she shall assume that it does exist and act accordingly.” The most safety-critical of the doubt rules, because the consequence of guessing wrong here is a closing, end-on approach. See Chapter 6; Part III scenarios.
Rule 15: Crossing Situation
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When two power-driven vessels are crossing so as to involve risk of collision, the vessel which has the other on her own starboard side shall keep out of the way and shall, if the circumstances of the case admit, avoid crossing ahead of the other vessel.
ANNOTATION
When two power-driven vessels are crossing so as to involve risk of collision, “the vessel which has the other on her own starboard side shall keep out of the way and shall, if the circumstances of the case admit, avoid crossing ahead of the other vessel.” Two phrases carry the Rule: “on her own starboard side” identifies the give-way vessel, and “avoid crossing ahead,” conditioned by “if the circumstances of the case admit,” is the secondary duty that points the give-way vessel towards a starboard alteration passing under the other’s stern. See Chapter 8; Rule 16; Part III scenarios.
Rule 16: Action by the Give-way Vessel
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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.
ANNOTATION
The give-way vessel shall “so far as possible, take early and substantial action to keep well clear.” Three key phrases: “so far as possible” (the strong qualifier, yielding only to genuine impossibility); “early and substantial” (not late and not token); and “keep well clear” (a wider margin than “keep out of the way,” the manner of compliance Cockcroft draws out). See Chapter 6; keep clear / keep well clear in the Glossary.
Rule 17: Action by the Stand-on Vessel
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(a)
(i) Where one of two vessels is to keep out of the way the other shall keep her course and speed.
(ii) The latter vessel may however take action to avoid collision by her manoeuvre alone, as soon as it becomes apparent to her that the vessel required to keep out of the way is not taking appropriate action in compliance with these Rules.
(b) When, from any cause, the vessel required to keep her course and speed finds herself so close that collision cannot be avoided by the action of the give-way vessel alone, she shall take such action as will best aid to avoid collision.
(c) A power-driven vessel which takes action in a crossing situation in accordance with sub-paragraph (a)(ii) of this Rule to avoid collision with another power-driven vessel shall, if the circumstances of the case admit, not alter course to port for a vessel on her own port side.
(d) This Rule does not relieve the give-way vessel of her obligation to keep out of the way.
ANNOTATION
(a)(i) Hold. The stand-on vessel “shall keep her course and speed.” The duty exists so the give-way vessel has a predictable target to plan around; it is not a privilege to be enjoyed but an obligation owed (Chapter 8). See stand-on vessel in the Glossary.
(a)(ii) The permission. She “may however take action to avoid collision by her manoeuvre alone, as soon as it becomes apparent” that the give-way vessel “is not taking appropriate action.” The word is “may”: this is permission, the Stage 3 turning point. See Chapter 8.
(b) The command. 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 word shifts to “shall”: permission has become duty, Stage 4. The contrast between “may” at (a)(ii) and “shall” at (b) is the most important “may versus shall” in the Rules. See Chapter 8; Figure 8-1.
(c) The port-turn restriction. A power-driven vessel taking action under (a)(ii) in a crossing situation “shall, if the circumstances of the case admit, not alter course to port for a vessel on her own port side.” It stops the stand-on vessel turning into the give-way vessel. The restriction lifts once (b) bites. See Chapter 9.
(d) Savings. This Rule “does not relieve the give-way vessel of her obligation to keep out of the way.” Both duties coexist; the stand-on vessel acting does not let the give-way vessel off. See Rule 16.
Rule 18: Responsibilities Between Vessels
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Except where Rules 9, 10, and 13 otherwise require:
(a) A power-driven vessel underway shall keep out of the way of:
(i) a vessel not under command;
(ii) a vessel restricted in her ability to manoeuvre;
(iii) a vessel engaged in fishing;
(iv) a sailing vessel.
(b) A sailing vessel underway shall keep out of the way of:
(i) a vessel not under command;
(ii) a vessel restricted in her ability to manoeuvre;
(iii) a vessel engaged in fishing.
(c) A vessel engaged in fishing when underway shall, so far as possible, keep out of the way of:
(i) a vessel not under command;
(ii) a vessel restricted in her ability to manoeuvre.
(d)
(i) Any vessel other than a vessel not under command or a vessel restricted in her ability to manoeuvre shall, if the circumstances of the case admit, avoid impeding the safe passage of a vessel constrained by her draught, exhibiting the signals in Rule 28.
(ii) A vessel constrained by her draught shall navigate with particular caution having full regard to her special condition.
(e) A seaplane on the water shall, in general, keep well clear of all vessels and avoid impeding their navigation. In circumstances, however, where risk of collision exists, she shall comply with the Rules of this Part.
(f)
(i) A WIG craft shall, when taking off, landing and in flight near the surface, keep well clear of all other vessels and avoid impeding their navigation;
(ii) a WIG craft operating on the water surface shall comply with the Rules of this Part as a power-driven vessel.
ANNOTATION
The order of precedence between classes, opening with the override “except where Rules 9, 10 and 13 otherwise require,” which is why overtaking (Rule 13) and the narrow-channel and traffic-scheme duties sit above this order. The ladder: a power-driven vessel keeps out of the way of a vessel not under command, one restricted in her ability to manoeuvre, one engaged in fishing, and a sailing vessel (a); a sailing vessel keeps out of the way of the first three (b); a vessel engaged in fishing shall “so far as possible” keep out of the way of a vessel not under command and one restricted in her ability to manoeuvre (c). Under (d)(i) any vessel except one not under command or restricted in her ability to manoeuvre shall, if the circumstances admit, “avoid impeding the safe passage” of a vessel constrained by her draught, and under (d)(ii) the constrained vessel shall “navigate with particular caution.” Paragraph (e) requires a seaplane to “keep well clear of all vessels and avoid impeding their navigation,” and (f) sets the WIG craft duties. The ladder is the subject of Figure 18-1, and the recurring trap is that a vessel constrained by her draught sits outside the ladder because she is a power-driven vessel (Rule 3(h)). See Chapter 7; Figure 18-1; Rule 13; constrained by her draught in the Glossary.
Section III: Conduct of Vessels in Restricted Visibility (Rule 19)
Rule 19: Conduct of Vessels in Restricted Visibility
THE RULE · MISCPUB 0127
(a) This Rule applies to vessels not in sight of one another when navigating in or near an area of restricted visibility.
(b) Every vessel shall proceed at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility. A power-driven vessel shall have her engines ready for immediate manoeuvre.
(c) Every vessel shall have due regard to the prevailing circumstances and conditions of restricted visibility when complying with the Rules of Section I of this Part.
(d) A vessel which detects by radar alone the presence of another vessel shall determine if a close-quarters situation is developing and/or risk of collision exists. If so, she shall take avoiding action in ample time, provided that when such action consists of an alteration of course, so far as possible the following shall be avoided:
(i) an alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken;
(ii) an alteration of course towards a vessel abeam or abaft the beam.
(e) Except where it has been determined that a risk of collision does not exist, every vessel which hears apparently forward of her beam the fog signal of another vessel, or which cannot avoid a close-quarters situation with another vessel forward of her beam, shall reduce her speed to the minimum at which she can be kept on her course. She shall if necessary take all her way off and in any event navigate with extreme caution until danger of collision is over.
ANNOTATION
(a) Scope. The Rule applies “to vessels not in sight of one another when navigating in or near an area of restricted visibility.” This is the section the visibility state routes to when Section II is shut out; there is no give-way or stand-on vessel here. See Chapter 5; Rule 3(k).
(b) Speed and readiness. Every vessel proceeds “at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility,” and a power-driven vessel keeps “her engines ready for immediate manoeuvre.” Note “adapted to,” another of the “to” qualifiers (Chapter 6). See Rule 6.
(c) Compliance with Section I. Every vessel has “due regard to the prevailing circumstances and conditions of restricted visibility” when complying with Section I. The fog colours how the universal Rules are applied. See Rule 4.
(d) Action on radar alone. A vessel that detects “by radar alone” the presence of another shall determine whether a close-quarters situation is developing or risk of collision exists, and if so “take avoiding action in ample time.” Two restrictions follow when that action is an alteration of course: under (d)(i) avoid “an alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken,” and under (d)(ii) avoid “an alteration of course towards a vessel abeam or abaft the beam.” The port-turn restriction hedges against the classic fog blunder of two vessels turning into each other (Chapter 9). See Chapter 9; Rule 8.
(e) Extreme caution. Except where risk of collision has been determined not to exist, every vessel that hears “apparently forward of her beam” the fog signal of another, or cannot avoid a close-quarters situation with a vessel forward of the beam, shall reduce to “the minimum at which she can be kept on her course,” and if necessary “take all way off,” and in any event “navigate with extreme caution until danger of collision is over.” This is the strongest caution grading and the only use of “danger of collision,” which reads as the end-of-encounter phase rather than a second defined trigger. See Chapter 6; extreme caution and danger of collision in the Glossary.
Part C (Rules 20 to 31) and Part D (Rules 32 to 37) follow, with the lights, shapes and sound-signal detail carried by the recognition tables in the visuals pass.