COLREGs for the OOW: Steering and Sailing Rules

Prerequisites

You should know the COLREGs at RYA Yachtmaster Offshore level: the lights, shapes and sound signals, and the basic give-way and stand-on rules. You should have read the lessons on keeping a navigational watch and on bridge resource management, and you should understand radar plotting, CPA and TCPA, and the use of ARPA. This lesson goes through Rules 1 to 19 at the depth the MCA oral examiner expects from an officer of the watch on a large ship.

Learning Objectives

By the end of this lesson you will be able to:

• Explain the scope and structure of the COLREGs and the meaning of Rule 2, responsibility.
• Apply Rule 5 (lookout) and Rule 6 (safe speed) to a large ship, including the extra radar factors.
• Determine risk of collision using compass bearings and range, and explain the limits of that method (Rule 7).
• Plan collision-avoiding action that meets every part of Rule 8, including when to use speed.
• Apply Rules 9 and 10 in narrow channels and traffic separation schemes.
• Identify overtaking, head-on and crossing situations (Rules 13 to 15) and the duties of give-way and stand-on vessels (Rules 16 and 17).
• Apply the Rule 18 responsibilities between vessels, including vessels constrained by their draught.
• Act correctly in restricted visibility under Rule 19.
• Learn from collisions where these rules were misapplied.

The Structure of the Rules

The International Regulations for Preventing Collisions at Sea, 1972 (COLREGs) are made law in the UK by the Merchant Shipping (Distress Signals and Prevention of Collisions) Regulations 1996; MSN 1781 (M+F) sets out the rules as they apply to UK ships. They have five parts and four annexes:

The sections of Part B are the key to applying them. Section I applies in any condition of visibility. Section II applies only to vessels in sight of one another. Section III applies to vessels not in sight of one another when navigating in or near an area of restricted visibility. The give-way and stand-on duties of Rules 13 to 18 do not exist between two ships that cannot see each other, a point many accidents have turned on.

Part A: General

Rule 1: application

The rules apply to all vessels upon the high seas and all waters connected with them navigable by seagoing vessels. Local authorities can make special rules for roadsteads, harbours, rivers, lakes and inland waterways, and these take precedence locally (for example, port byelaws and the rules for some UK rivers). Know the local rules for every port you enter: they are in the sailing directions and the port information.

Rule 2: responsibility

Rule 2 has two parts, and the oral examiner will expect you to explain both:

• Rule 2(a): nothing in the rules exonerates anyone from the consequences of neglecting to comply with them, or of neglecting any precaution required by the ordinary practice of seamen or the special circumstances of the case.
• Rule 2(b): in construing and complying with the rules, due regard shall be had to all dangers of navigation and collision and to any special circumstances, including the limitations of the vessels involved, which may make a departure from the rules necessary to avoid immediate danger.

Rule 2(b) is not a licence to ignore the rules when they are inconvenient. It applies only when following the rules would itself lead into immediate danger, for example when three ships meet and the action required by one rule would cause a collision with another vessel.

Rule 3: definitions

The definitions you must know exactly include: vessel; power-driven vessel; sailing vessel (a vessel under sail with propelling machinery, if fitted, not being used); vessel engaged in fishing (using nets, lines, trawls or other gear that restricts manoeuvrability, but not trolling lines); seaplane; not under command (through some exceptional circumstance unable to manoeuvre as required by the rules); restricted in her ability to manoeuvre (by the nature of her work, with a list of examples including dredging, cable laying, replenishment under way, launching or recovering aircraft, mine clearance and towing that severely restricts the ability to deviate); constrained by her draught (a power-driven vessel severely restricted in her ability to deviate from her course because of her draught in relation to the available depth and width of water); under way (not at anchor, made fast to the shore or aground); in sight of one another (only when one can be observed visually from the other); restricted visibility (any condition in which visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms or any similar causes); and WIG craft.

Note that "under way" does not require making way: a ship stopped in the water is under way.

Section I: Any Condition of Visibility

Rule 5: lookout

Every vessel shall at all times maintain a proper lookout 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. On a large ship, "all available means" includes both radars on appropriate ranges, ARPA, AIS and VHF, but the eye and ear come first. The watchkeeping lesson covers the lookout arrangements under STCW and MGN 315.

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 circumstances. The factors to consider are:

By all vessels:

• the state of visibility;
• the traffic density, including concentrations of fishing vessels or any other vessels;
• the manoeuvrability of the vessel, with special reference to stopping distance and turning ability in the prevailing conditions;
• at night, the presence of background light such as from shore lights or from back scatter of her own lights;
• the state of wind, sea and current, and the proximity of navigational hazards;
• the draught in relation to the available depth of water.

Additionally, by vessels with operational radar:

• the characteristics, efficiency and limitations of the radar equipment;
• any constraints imposed by the radar range scale in use;
• the effect on radar detection of the sea state, weather and other sources of interference;
• the possibility that small vessels, ice and other floating objects may not be detected by radar at an adequate range;
• the number, location and movement of vessels detected by radar;
• the more exact assessment of the visibility that may be possible when radar is used to measure the range of vessels or other objects in the vicinity.

For a large ship, the stopping distance is the factor that surprises people. A loaded VLCC at full sea speed may need several nautical miles and well over ten minutes for a crash stop. The wheelhouse poster gives your ship's figures. Safe speed in fog is the speed at which you could stop, or take effective avoiding action, within the distance you can rely on detecting a small vessel.

Rule 7: risk of collision

Rule 7 tells you how to decide whether risk of collision exists:

• 7(a): every vessel shall use all available means appropriate to the circumstances to determine if risk of collision exists. If there is any doubt, such risk shall be deemed to exist.
• 7(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.
• 7(c): assumptions shall not be made on the basis of scanty information, especially scanty radar information.
• 7(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.

The diagram shows what a steady bearing means in practice.

Click to zoom

Taking compass bearings properly

• Use a compass bearing (gyro repeater or the radar's true bearing with a stabilised display), not a relative bearing. A relative bearing changes every time your own ship yaws or alters course.
• Take a series of bearings, with times and ranges. Three bearings over six minutes is a typical minimum in open sea; more when the range is short.
• "Appreciably" is judged against the range: a 1° change at 10 nm is meaningless, while at 1 nm a ship with a steady bearing is about to hit you.
• With a very large ship or a tow, the bearing of the bridge or masthead lights can change while the bow or the tow on the end of a 600 m wire is still heading for you. Rule 7(d)(ii) exists for this.
• Combine visual bearings with radar range and ARPA data. The ARPA gives you CPA and TCPA, but they are only as good as the inputs: heading and speed sensors, the time since acquisition, and the target's own steadiness. Wait for a stable track (typically about three minutes for a full vector) before trusting the numbers.

Rule 8: action to avoid collision

Rule 8 tells you what kind of action to take. Read every word; examiners do.

• 8(a): any action shall be taken in accordance with the rules of Part B 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.
• 8(b): any alteration of course and/or speed shall, if the circumstances admit, be large enough to be readily apparent to another vessel observing visually or by radar; a succession of small alterations should be avoided.
• 8(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.
• 8(d): action 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.
• 8(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.
• 8(f): a vessel required not to impede the passage of another shall, when required by the circumstances, take early action to allow sufficient sea room for the safe passage of the other vessel. She 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 rules of Part B. A vessel whose passage is not to be impeded remains fully obliged to comply with Part B when the two vessels are approaching so as to involve risk of collision.

What "readily apparent" means

An alteration of course of 10° is unlikely to be noticed by another ship's OOW, either visually or on radar. As a rule of thumb, alterations of at least 30°, and often 60° or more, are needed to be readily apparent, and a combination of alterations totalling the same angle is not as clear as one bold turn. On radar, the other ship sees your heading change only when its ARPA has re-stabilised your track, so a large, early alteration gives it the best chance of understanding you.

Using speed

Big ships are often reluctant to reduce speed: engines on bridge control can be changed quickly, but a slow-speed diesel may have limits on how fast it can be reduced, and slowing affects schedules. None of that is an excuse. Rule 8(e) says to reduce speed or stop when necessary. Remember that a reduction of speed takes time to take effect on a large ship and is hard for the other vessel to see, so it is usually combined with an alteration of course, and in restricted visibility it is often the right first action.

Narrow Channels and Traffic Separation Schemes

Rule 9: narrow channels

• A vessel proceeding along a narrow channel or fairway shall keep as near to the outer limit on her starboard side as is safe and practicable.
• A vessel of less than 20 m in length or a sailing vessel shall not impede the passage of a vessel that can safely navigate only within the channel.
• A vessel engaged in fishing shall not impede the passage of any other vessel navigating within the channel.
• A vessel shall not cross a narrow channel if such crossing impedes the passage of a vessel that can safely navigate only within it. The latter may use the doubtful signal (at least five short and rapid blasts) if in doubt as to the crossing vessel's intention.
• Overtaking in a narrow channel, where the overtaken vessel must take action to permit safe passing: the overtaking vessel signals two prolonged blasts followed by one short (overtake on your starboard side) or two short (on your port side); the overtaken vessel agrees with prolonged, short, prolonged, short. Rule 13 still applies.
• A vessel nearing a bend where other vessels may be obscured by an intervening obstruction sounds one prolonged blast, answered by any approaching vessel round the bend.
• Every vessel shall, if the circumstances admit, avoid anchoring in a narrow channel.

Rule 10: traffic separation schemes

Rule 10 applies to TSS adopted by the IMO (see the Ships' Routeing publication and the chart), and does not relieve any vessel of her obligations under any other rule. Its main duties:

• A vessel using a TSS shall proceed in the appropriate traffic lane in the general direction of traffic flow for that lane, keep clear of a separation line or zone as far as practicable, and normally join or leave at the termination of the lane, or if joining or leaving from either side, at as small an angle to the general direction of flow as practicable.
• 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. The rule is about heading, not track: the ship presents a clear right-angled aspect to the lane traffic and spends the least time in the lane, even if the tidal stream sets her diagonally.
• A vessel shall not use an inshore traffic zone when she can safely use the appropriate lane in the adjacent TSS. Vessels of less than 20 m, sailing vessels and vessels engaged in fishing may use it, and so may other vessels when en route to or from a port, offshore installation, pilot station or other place within the zone, or to avoid immediate danger.
• A vessel other than a crossing vessel or one joining or leaving a lane shall not normally enter a separation zone or cross a separation line, except in an emergency to avoid immediate danger or to engage in fishing within it.
• Vessels navigating near the terminations of a TSS shall do so with particular caution.
• A vessel shall so far as practicable avoid anchoring in a TSS or near its terminations.
• A vessel not using a TSS shall avoid it by as wide a margin as practicable.
• A vessel engaged in fishing shall not impede the passage of any vessel following a traffic lane.
• A vessel of less than 20 m or a sailing vessel shall not impede the safe passage of a power-driven vessel following a traffic lane.
• Vessels restricted in their ability to manoeuvre when engaged in maintaining safety of navigation, or in laying, servicing or picking up a submarine cable, in a TSS are exempt from complying with Rule 10 to the extent necessary to carry out the operation.

Two key exam points:

1. Being in a lane gives no right of way. A large ship in the north-east lane of the Dover Strait meeting a ship crossing from her starboard side is the give-way vessel under Rule 15, unless the crossing vessel is one required not to impede (under 20 m, sailing, or fishing). The examiner will ask this.
2. Reporting: many schemes have mandatory ship reporting (for example CALDOVREP in the Dover Strait) and VTS monitoring. Report as required, but do not use VTS as a substitute for the rules.

Section II: Vessels in Sight of One Another

Which situation is it?

The diagram shows where the other vessel can be relative to you, and which rule then applies between two power-driven vessels.

Click to zoom

Rule 13: overtaking

• Any vessel overtaking any other shall keep out of the way of the vessel being overtaken. This applies whatever the vessel types: a sailing vessel overtaking a power-driven vessel keeps out of the way; so does a fishing vessel overtaking anything.
• A vessel is overtaking when coming up with another from a direction more than 22.5° abaft her beam, that is, in such a position that at night she would see only the sternlight and neither sidelight.
• When in doubt whether she is overtaking, a vessel shall assume she is and act accordingly.
• Any subsequent alteration of the bearing between the two vessels does not make the overtaking vessel a crossing vessel, or relieve her of the duty to keep clear until she is finally past and clear.

Rule 14: head-on

• When two power-driven vessels are meeting on reciprocal or nearly reciprocal courses so as to involve risk of collision, each shall alter course to starboard so that each passes on the port side of the other.
• Such a situation exists 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/or both sidelights, and by day observes the corresponding aspect.
• When in doubt whether such a situation exists, assume it does and act accordingly.

"Nearly ahead" is not defined in the rule. Authorities such as Cockcroft and Lameijer suggest about 6° either side of the bow, matching the area in which you can see both sidelights. Outside it, treat it as crossing.

Rule 15: crossing

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 admit, avoid crossing ahead of the other vessel.

The usual action is a substantial alteration to starboard to pass astern of the other vessel. Slowing down, or a round turn to starboard in confined waters, are alternatives. An alteration to port to pass ahead is almost always wrong.

Rule 16: action by the give-way vessel

Every vessel directed to keep out of the way of another shall, so far as possible, take early and substantial action to keep well clear.

Rule 17: action by the stand-on vessel

Rule 17 gives the stand-on vessel a sequence of duties:

1. 17(a)(i): where one vessel is to keep out of the way, the other shall keep her course and speed.
2. 17(a)(ii): the stand-on vessel may 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. She should first sound at least five short and rapid blasts (Rule 34(d)).
3. 17(b): when, from any cause, the stand-on vessel 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.
4. 17(c): a power-driven vessel that takes action under 17(a)(ii) to avoid collision with another power-driven vessel in a crossing situation shall, if the circumstances admit, not alter course to port for a vessel on her own port side.
5. 17(d): this rule does not relieve the give-way vessel of her obligation to keep out of the way.

For a large ship standing on, the point at which "the give-way vessel is not taking appropriate action" must be judged against your own ship's handling. If your ship needs 1.5 nm to turn clear, you cannot wait until the give-way vessel is at 1 nm to decide. Standing orders often set a range at which the master must be called and action considered.

When you alter under 17(a)(ii) for a vessel crossing from your port side, the usual action is a substantial turn to starboard, often a round turn, to pass astern of it, or a large reduction of speed. Turning to port, towards the vessel that may at last be turning to starboard, is the classic error that 17(c) forbids.

Rule 18: responsibilities between vessels

Except where Rules 9, 10 and 13 otherwise require, Rule 18 sets out who keeps out of whose way, as the diagram shows.

Click to zoom

• A power-driven vessel under way shall keep out of the way of a vessel not under command, a vessel restricted in her ability to manoeuvre, a vessel engaged in fishing, and a sailing vessel.
• A sailing vessel under way shall keep out of the way of a vessel not under command, a vessel restricted in her ability to manoeuvre, and a vessel engaged in fishing.
• A vessel engaged in fishing when under way shall, so far as possible, keep out of the way of a vessel not under command and a vessel restricted in her ability to manoeuvre.
• Any vessel other than a vessel not under command or 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 (three all-round red lights in a vertical line, or a cylinder). A vessel constrained by her draught shall navigate with particular caution having full regard to her special condition.
• A seaplane on the water shall in general keep well clear of all vessels and avoid impeding their navigation. A WIG craft taking off, landing and in flight near the surface shall keep well clear of all other vessels and avoid impeding their navigation.

Note the words "except where Rules 9, 10 and 13 otherwise require". A fishing vessel in a narrow channel must not impede a ship that can navigate only in the channel. A sailing vessel overtaking a power-driven vessel must keep clear of it.

Section III: Restricted Visibility

Rule 19

Rule 19 applies to vessels not in sight of one another when navigating in or near an area of restricted visibility. Its duties:

• 19(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.
• 19(c): every vessel shall have due regard to the prevailing circumstances and restricted visibility when complying with the rules of Section I.
• 19(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.
• 19(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.

The diagram shows the Rule 19(d) logic.

Click to zoom

Points the examiner will probe

• There is no stand-on vessel in Rule 19. Every vessel has the same duty to take avoiding action if a close-quarters situation is developing. A ship approaching from your port bow in fog is not "the give-way vessel".
• Close-quarters is not defined in figures. In open sea, many masters treat 2 to 3 nm as the start of close quarters for a large ship in fog; in coastal waters it may be less. Your standing orders will say.
• Radar only. Rule 19(d) is about vessels detected by radar alone. Once the ships are in sight of one another, Section II applies.
• Sound signals: in or near restricted visibility, a power-driven vessel making way sounds one prolonged blast at intervals of not more than 2 minutes; stopped and making no way, two prolonged blasts with about 2 seconds between them at intervals of not more than 2 minutes (Rule 35).
• The precautions for entering restricted visibility come from good practice and MGN 369: call the master, post extra lookouts, hand steering, engines on stand-by, safe speed, sound signals, radar plotting on suitable ranges, navigation lights on, and close watertight doors as required.

Why port turns in fog kill

In July 1956, the Italian liner Andrea Doria and the Swedish liner Stockholm approached each other near Nantucket. Andrea Doria was in fog, and saw Stockholm on radar fine on her starboard bow. She altered to port to open the passing distance. Stockholm saw Andrea Doria on radar fine on her port bow and altered to starboard. The two turns brought the ships together; Stockholm's bow cut into Andrea Doria's side and 46 people on the liner died. Rule 19(d) as it is written today was shaped by collisions like this. Neither ship should have turned towards the other's side of the bow, and both were going too fast for the visibility.

Communication and Signals in Collision Avoidance

• Rule 34(a): when vessels are in sight of one another, a power-driven vessel under way, when manoeuvring as authorised or required by the rules, shall indicate that manoeuvre by whistle: one short blast, "I am altering my course to starboard"; two short, "I am altering my course to port"; three short, "I am operating astern propulsion". These may be supplemented by light signals.
• Rule 34(d): when vessels in sight of one another are approaching and either fails to understand the intentions or actions of the other, or is in doubt whether sufficient action is being taken, she shall immediately indicate the doubt by at least five short and rapid blasts.
• VHF: MCA guidance warns against using VHF to agree collision avoidance manoeuvres. Identification of the other ship can be uncertain (AIS and VHF identifications have been confused), time is lost talking, and an agreement to pass "starboard to starboard" may contradict the rules and mislead a third ship. Use VHF, if at all, to make your intentions known, and always act in accordance with the rules.

Worked Example: A Crossing Situation by Radar and Eye

You are OOW on a 60,000 GT tanker heading 000° at 15 knots in open sea, clear visibility, at night. Standing orders: minimum CPA 2 nm in open sea.

1200. A target is detected and acquired: bearing 030°, range 8.0 nm. Visually you see two masthead lights, the lower forward light to the left of the higher after light, and a red sidelight.

1206. Bearing 030°, range 6.6 nm. The compass bearing has not changed and the range is closing at about 14 knots. Risk of collision exists (Rule 7(d)(i)). The ARPA gives the target's course as 290° and speed 7.6 knots, CPA 0.0 nm, TCPA 28 minutes.

Assess. The other vessel is a power-driven vessel on your starboard bow, showing its port side, crossing from starboard to port. This is a Rule 15 crossing situation and you are the give-way vessel. Rule 16: early and substantial action. Rule 15: avoid crossing ahead.

Plan with the trial manoeuvre. You use the ARPA trial function:

1210. At 5.6 nm you alter 40° to starboard, to 040°, with one short blast. The 40° turn is large enough to be readily apparent (Rule 8(b)), it is made in ample time (Rule 8(a)), it does not create a new close-quarters situation with other traffic (Rule 8(c)), and it passes at a safe distance (Rule 8(d)). You tell the lookout, and if the master's standing orders require it, you inform the master.

1215 onwards. You check the effectiveness: the bearing is now drawing left steadily, and the ARPA CPA settles at about 3.0 nm. The target will cross ahead of your original track and pass clear on your port bow. Rule 8(d): keep checking until the other vessel is finally past and clear.

About 1230. The target is past and clear on your port side, its bearing drawing aft and the range opening. You return to the planned track and log the events.

Notice what a timid 10° or 20° turn would have done: a CPA scarcely above the minimum, and a manoeuvre the other ship might not notice, inviting it to make a late and confusing turn of its own.

Case Study: The Stand-On Vessel That Waited Too Long

A large container ship is standing on, with a smaller cargo ship crossing from her port side. The give-way ship's OOW is busy with paperwork and does not act. At 3 nm, the container ship's OOW calls on VHF, gets no answer, and decides to keep waiting "because we are the stand-on vessel". At 1.5 nm, he sounds five short blasts. At 0.8 nm, he finally turns hard to port, towards the other ship, to "go round its stern". At the same moment, woken by the signal, the other OOW turns hard to starboard. They collide.

What went wrong:

• The stand-on OOW was entitled to act under 17(a)(ii) much earlier, as soon as it was apparent the other ship was not giving way, and for a big ship that point comes early.
• By the time he acted, 17(b) obliged him to take the best action to avoid collision.
• He turned to port for a vessel on his own port side, the very action 17(c) says to avoid. A turn to starboard, ideally combined with a large reduction of speed, would have opened the distance even if the other ship turned to starboard too.
• He relied on VHF instead of the rules.

Common Mistakes

• Using relative bearings to judge risk. Use compass bearings, and remember Rule 7(d)(ii) for big ships, tows and close range.
• Trusting early ARPA data. Wait for a stable track; scanty radar information is no basis for assumptions.
• Small, repeated alterations. Rule 8(b): make one bold, early, obvious alteration.
• Turning to port for a crossing vessel on your starboard side to pass ahead of it. Rule 15 says avoid crossing ahead.
• Thinking a TSS lane gives priority. It does not, except over vessels required not to impede.
• Applying Section II rules in fog. There is no stand-on vessel when ships are not in sight of one another.
• Turning to port for a radar contact forward of the beam in fog, or turning towards a contact abeam or abaft.
• Agreeing manoeuvres on VHF contrary to the rules, or with a ship you have not positively identified.
• Stand-on vessels waiting too long. Know your ship's turning circle and act under 17(a)(ii) in time.

Summary

• The COLREGs Part B has three sections: any visibility (Rules 4 to 10), in sight of one another (11 to 18), and restricted visibility (19). Know which applies before deciding what to do.
• Rule 2: the rules never excuse bad seamanship, and departure from them is allowed only to avoid immediate danger.
• Rule 5 and Rule 6: proper lookout by all available means; safe speed using all the listed factors, including radar limitations and your ship's stopping distance.
• Rule 7: if the compass bearing does not appreciably change, risk exists; if in doubt, it exists; big ships, tows and close range can mislead you.
• Rule 8: positive, early, substantial, readily apparent action, passing at a safe distance, checked until clear; use speed when needed.
• Rules 9 and 10: keep to starboard in channels; in a TSS follow the lane, cross at right angles in heading, and remember that lane traffic has no general right of way.
• Rules 13 to 17: overtaking keeps clear; head-on both turn to starboard; in a crossing, the vessel with the other on her starboard side gives way and avoids crossing ahead; the stand-on vessel keeps course and speed, may act, must act when close, and avoids turning to port for a vessel on her port side.
• Rule 18: power keeps clear of sailing, fishing, RAM and NUC; everyone avoids impeding a vessel constrained by her draught.
• Rule 19: safe speed, engines ready; with a radar-only contact, avoid port turns for vessels forward of the beam and turns towards vessels abeam or abaft; slow right down for a fog signal forward of the beam.

Check Your Understanding

1. In what conditions does Rule 15 not apply between two power-driven vessels on crossing courses?

Answer: When they are not in sight of one another, for example in fog with each detecting the other only by radar. Then Rule 19 applies and neither is the stand-on vessel.

1. A target's compass bearing has changed by 3° in 6 minutes while the range closed from 3 nm to 2 nm. It is a large tanker towing a barge. Does risk of collision exist?

Answer: It may well do. Rule 7(d)(ii) says risk may exist even with an appreciable bearing change, particularly with a very large vessel, a tow, or at close range. If in doubt, risk is deemed to exist (Rule 7(a)).

1. List four requirements of Rule 8 for action to avoid collision.

Answer: Any four of: positive; made in ample time; with due regard to good seamanship; large enough to be readily apparent; avoid a succession of small alterations; result in passing at a safe distance; effectiveness checked until finally past and clear; slacken speed or take all way off if necessary.

1. You must cross a TSS. The tidal stream is setting along the lane at 3 knots. What heading do you steer?

Answer: A heading as nearly as practicable at right angles to the general direction of traffic flow. Rule 10 refers to the heading, not the track, so you accept being set diagonally.

1. You are a 200 m bulk carrier in a TSS lane. A 15 m yacht under sail is crossing ahead from your starboard side with risk of collision. Who gives way?

Answer: The yacht must not impede the safe passage of a power-driven vessel following a traffic lane (Rule 10(j)). It should take early action to leave you sea room (Rule 8(f)). If risk of collision still develops, both vessels must comply with Part B; you remain a power-driven vessel required by Rule 18 to keep out of the way of a sailing vessel, so you must be ready to act.

1. You are the stand-on vessel and the give-way vessel, crossing from your port side, has not acted. What may you do, and what must you avoid?

Answer: After sounding at least five short and rapid blasts, you may take action by your own manoeuvre alone (Rule 17(a)(ii)), and if collision cannot be avoided by the give-way vessel alone you must take the best action to avoid it (17(b)). If circumstances admit, do not alter course to port for a vessel on your own port side (17(c)).

1. In fog, you detect by radar alone a vessel 20° on your port bow, closing with a steady bearing. Which way should you avoid altering?

Answer: Avoid altering to port, because it is forward of the beam and you are not overtaking it (Rule 19(d)(i)). An alteration to starboard and/or a reduction of speed is appropriate.

1. In fog you hear a fog signal apparently forward of your beam. What does Rule 19(e) require?

Answer: Unless you have determined that risk of collision does not exist, reduce speed to the minimum at which you can keep your course, take all way off if necessary, and navigate with extreme caution until the danger of collision is over.

1. What is the sound signal meaning "I am altering my course to starboard", and when is it used?

Answer: One short blast. A power-driven vessel uses it when in sight of another vessel and manoeuvring as authorised or required by the rules (Rule 34(a)).

1. Why does the head-on rule apply only to power-driven vessels, and what is the action?

Answer: Rule 14 is written for two power-driven vessels, because sailing vessels have their own rule (Rule 12) and other vessel types are covered by Rule 18. In a head-on situation each vessel alters course to starboard so that they pass port to port.

Further Reading

• COLREGs 1972, consolidated edition (IMO)
• MSN 1781 (M+F) Amendment 3: the COLREGs as UK law
• A.N. Cockcroft and J.N.F. Lameijer, A Guide to the Collision Avoidance Rules, 7th edition (Butterworth-Heinemann)
• MGN 369 (M+F) Amendment 1: navigation practices in restricted visibility
• A.G. Bole, A. Wall and A. Norris, Radar and ARPA Manual, 3rd edition (Butterworth-Heinemann)
• IMO Resolution MSC.192(79): radar (and ARPA/ATA) performance standards
• IMO Model Course 1.07: Radar Navigation at Operational Level