COLREGs, Traffic Separation and Restricted Visibility

Prerequisites

This lesson is pitched at RYA Coastal Skipper / Yachtmaster Coastal level. Before starting you should:

• Hold, or be working at the standard of, the RYA Day Skipper shorebased and practical certificates, including the basic steering and sailing rules (Rules 5 to 18), the lights and shapes for common vessels and the manoeuvring sound signals.
• Meet (or be working towards) the Coastal Skipper practical course entry level: at least 15 days at sea, 2 days as skipper, 300 nautical miles and 8 night hours, minimum age 17. The Yachtmaster Coastal exam requires 30 days, 2 days as skipper, 800 miles and 12 night hours, plus a GMDSS radio certificate (SRC or higher) and a valid first aid certificate.
• Be comfortable with radar and AIS basics (CPA, TCPA, relative motion) from the radar and AIS lesson, since restricted visibility work relies on them.

Learning Objectives

This lesson covers the collision regulations (IRPCS) element of the RYA Coastal Skipper / Yachtmaster Offshore shorebased syllabus and the IRPCS knowledge assessed in the Yachtmaster Coastal practical exam. By the end you will be able to:

• Apply the steering and sailing rules (Rules 12 to 17) accurately in single and multi-vessel situations, including the stand-on vessel's rights and duties under Rule 17. (RYA syllabus: IRPCS, application of the rules in full.)
• Apply Rule 9 (narrow channels) including overtaking agreements and the bend signal, and explain who must not impede whom. (RYA syllabus: narrow channels and special local rules.)
• Apply Rule 10 (Traffic Separation Schemes): crossing on a heading at right angles, joining and leaving at a small angle, use of Inshore Traffic Zones and separation zones. (RYA syllabus: traffic separation schemes.)
• State the Rule 18 responsibilities between vessels and recognise each category by its lights and shapes (Rules 20 to 30). (RYA syllabus: lights, shapes and responsibilities between vessels.)
• Apply Rules 5 to 8 (lookout, safe speed, risk of collision, action to avoid collision) using radar and AIS plotting data such as bearing movement, CPA and TCPA. (RYA syllabus: radar and collision avoidance.)
• Apply Rule 19 (conduct in restricted visibility) correctly, including the forbidden alterations of course. (RYA syllabus: restricted visibility.)
• Give and recognise the Rule 35 sound signals in restricted visibility and the Rule 34 manoeuvring and warning signals. (RYA syllabus: sound and light signals.)
• Make sound skipper decisions in multi-vessel situations and explain your reasoning aloud, as expected in the Yachtmaster Coastal exam.

Why the Rules Matter More at Coastal Skipper Level

At Day Skipper level the rules are mostly about one-on-one encounters in good visibility. As a Coastal Skipper you will be crossing shipping lanes, entering commercial ports at night, using narrow dredged channels shared with ships that cannot leave them, and occasionally being caught out by fog. The examiner expects you to know the rules well enough to act instantly and to explain why a particular action is correct. Hesitating over a light configuration or turning the wrong way in fog is a fail point, because in real life it is how yachts get run down.

Remember the general rules that frame everything else:

• Rule 5 (Lookout): a proper lookout by sight, hearing and all available means (radar, AIS, VHF) at all times.
• Rule 6 (Safe speed): a speed at which you can take proper and effective action and stop within a distance appropriate to the conditions. Factors include visibility, traffic density, manoeuvrability, background lights at night, wind, sea and current, draught versus depth, and the characteristics and limitations of your radar.
• Rule 7 (Risk of collision): if in doubt, risk exists. A steady compass bearing with decreasing range means risk; with large ships at close range, risk can exist even when the bearing is changing appreciably.
• Rule 8 (Action to avoid collision): action must be positive, made in ample time, and large enough to be readily apparent to the other vessel visually or on radar. Small successive alterations are prohibited in spirit because nobody can read them. Reducing speed or stopping is always an option.

Responsibilities Between Vessels (Rule 18)

Rule 18 sets out which vessels keep out of the way of which, when they are in sight of one another. It does not apply in restricted visibility when vessels are not in sight of one another (that is Rule 19), and it is subject to Rules 9, 10 and 13. In other words, a sailing yacht overtaking a ship must still keep clear, and a sailing yacht in a narrow channel or TSS must still not impede a ship that can only navigate within it.

The diagram below shows the order. Each category keeps out of the way of the categories above it.

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A few refinements the diagram cannot show:

• Constrained by draught (CBD) is a special case. Other vessels (except NUC and RAM) shall, if circumstances permit, avoid impeding the safe passage of a CBD vessel. The CBD vessel itself must navigate with particular caution.
• A sailing vessel using her engine is a power-driven vessel, whatever sails are set. By day she should show a cone, point downwards, forward where best seen.
• Seaplanes and WIG craft keep well clear of all vessels and avoid impeding their navigation.
• Fishing means fishing with gear that restricts manoeuvrability (nets, trawls, lines). A boat trolling a line is not "engaged in fishing" under the rules.

Lights and shapes you must recognise instantly

The examiner will expect you to name these in under three seconds. Learn them by the logic: all-round lights describe status, masthead and sidelights describe underway and aspect.

The Steering and Sailing Rules Revisited (Rules 12 to 17)

The Coastal Skipper syllabus assumes you know the Day Skipper rules cold; the examiner will test them in combination with the more advanced rules. A quick but precise revision follows, because most real collisions happen through errors in these basics.

Rule 12: sailing vessels meeting each other

• Wind on different sides: the vessel with the wind on her port side (port tack) keeps clear of the vessel with the wind on her starboard side.
• Wind on the same side: the windward vessel keeps clear of the leeward vessel.
• If a vessel with the wind on the port side sees another to windward and cannot tell whether the other has the wind on the port or starboard side, she keeps clear.

The "side the wind is on" is the side opposite the mainsail. Running dead downwind with the main out on the port side means the wind is on the starboard side.

Rule 13: overtaking

Any vessel coming up with another from a direction more than 22.5 degrees abaft her beam, that is in a position where at night she could see only the sternlight of the other and neither sidelight, is overtaking. She keeps out of the way, whatever type of vessel she is. If in any doubt whether you are overtaking, assume you are. The duty continues until the overtaking vessel is finally past and clear, so a later change of bearing does not turn the overtaker into a crossing vessel.

Rule 14: head-on

Two power-driven vessels meeting on reciprocal or nearly reciprocal courses so as to involve risk of collision each alter course to starboard so each passes on the port side of the other. At night you would see both masthead lights in line or nearly in line and/or both sidelights; by day the masts in line. If in doubt, assume a head-on situation exists and act accordingly. Rule 14 applies only to power-driven vessels meeting each other; two sailing yachts meeting head-on are governed by Rule 12.

Rule 15 and 16: crossing and the give-way vessel

When two power-driven vessels cross so as to involve risk of collision, the vessel which has the other on her starboard side keeps out of the way and, if circumstances admit, avoids crossing ahead of the other. The give-way vessel (Rule 16) takes early and substantial action to keep well clear. The commonest failure of a yacht giving way to a ship is to alter by a few degrees and then wait; the ship's officer sees nothing change and the situation becomes critical. Alter by at least 30 to 60 degrees, or slow down so the ship passes ahead with room to spare.

Rule 17: the stand-on vessel

The stand-on vessel keeps her course and speed, but Rule 17 gives her important rights and duties which are frequently examined:

1. Rule 17(a)(ii): as soon as it becomes apparent that the give-way vessel is not taking appropriate action, the stand-on vessel may take action to avoid collision by her own manoeuvre alone.
2. In a crossing situation, if she does so she shall, if the circumstances allow, not alter course to port for a vessel on her own port side.
3. Rule 17(b): when she 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. Rule 17(a)(ii) is a permission only; in practice, a yacht that is stand-on against a ship should not wait until the last moment. Use the five short blasts doubt signal (Rule 34(d)) when you have decided that the ship is not acting, and then act: a bold turn to starboard or slowing down is usually best.

The rule that sits above all of these is Rule 2: nothing in the rules exonerates any vessel from the consequences of neglect of any precaution required by ordinary practice of seamen, or by the special circumstances of the case. A departure from the rules may be necessary to avoid immediate danger. Examiners like to hear a skipper say "the rules say I am stand-on, but I will not insist on that against a 30,000 tonne ship that has not seen me".

Rules 5 to 8 in Depth: Safe Speed, Risk and Radar Judgement

Rules 5 to 8 are the foundation of collision avoidance by a skipper who has radar and AIS. The Coastal Skipper candidate is expected to use them in a structured way rather than by instinct.

Assessing risk of collision (Rule 7)

Risk of collision is deemed to exist if the compass bearing of an approaching vessel does not appreciably change; it can also exist when the bearing changes appreciably if the vessel is very large, towing, or at close range (Rule 7(d)(i) and (ii)). Rule 7(c) forbids assumptions based on scanty information, especially scanty radar information. Rule 7(b) obliges you to use radar properly, including long-range scanning and radar plotting or systematic observation of detected objects.

A systematic way to judge a radar or visual contact:

1. Note the bearing and range of the target, and the time.
2. Note them again after 3 to 6 minutes. A constant bearing with falling range means a collision course.
3. Derive the closing speed: change in range divided by elapsed time.
4. Estimate the time to the closest point of approach (TCPA) and the closest point of approach distance (CPA), either on the radar's electronic plotting aid or by drawing a relative motion line.

Worked example: bearing movement and closing speed

At 0200 a ship shows on a steady relative bearing of 045 degrees (fine on your starboard bow), range 4.0 miles. At 0210 the bearing is still 045 degrees and the range is 3.0 miles.

• Closing speed = 1.0 mile in 10 minutes = 6 knots.
• Time to reach zero range = 3.0 / 6 = 0.5 hours = 30 minutes, so collision at about 0240 if neither vessel alters.
• The bearing is steady, so risk of collision exists. You are the give-way vessel (the ship is on your starboard side). With 30 minutes in hand you have time to act early and substantially. A turn of 50 degrees to starboard at 0215, or a speed reduction that lets the ship cross ahead with a CPA of at least 1 mile, will be seen clearly by the ship.

Contrast this with a ship at 0.5 mile range and a combined closing speed of 20 knots (your 5 knots plus her 15): you have only 1.5 minutes. The same lesson applies to restricted visibility: the range at which you detect a target must always give time for action.

Safe speed (Rule 6): the factors that count

Rule 6 lists factors for all vessels: state of visibility; traffic density including concentrations of fishing vessels; manoeuvrability including stopping distance and turning ability; at night, background light such as shore lights or backscatter from your own lights; wind, sea and current, and proximity of navigational hazards; draught in relation to available depth. For vessels with radar it adds: the characteristics, efficiency and limitations of the radar equipment; the constraints imposed by the radar range scale in use; the effect on radar detection of sea state, weather and other sources of interference; the possibility that small vessels, ice and other floating objects may not be detected at adequate range; the number, location and movement of vessels detected; and the more exact assessment of visibility possible when radar is used to determine the range of vessels or other objects in the vicinity.

For a small yacht the key point is that a small GRP or wooden yacht may be a poor radar target, and a ship may not see you at all. Safe speed for you is often lower than the speed that would be safe for a vessel carrying a high-performance radar, and a passive radar reflector (at least 10 square metres effective echoing area, ISO 8729, mounted as high as practicable) does not guarantee that you will be seen. Consider an active radar target enhancer or AIS Class B transponder, but do not treat either as a replacement for lookout and action.

Action to avoid collision (Rule 8)

Rule 8 requires that action be:

• Positive and taken in ample time, observing good seamanship.
• Large enough to be readily apparent to another vessel observing visually or by radar; a succession of small alterations of course or speed shall be avoided.
• Aimed at passing at a safe distance, and checked until the other vessel is finally past and clear.
• Supported by slowing down or taking all way off if needed to give more time (Rule 8(e)).
• A vessel required not to impede another (as in Rules 9 and 10) must take early action to allow sufficient sea room, and is not relieved of this duty if risk of collision develops (Rule 8(f)).

For a yacht, "large enough to be readily apparent" typically means 30 degrees or more, and combine it with a reduction in speed if the geometry is tight.

Lights, Shapes and Anchoring: Rules 20 to 30 for the Coastal Skipper

The table of lights earlier in this lesson summarises the status lights. The following practical points are drawn from Rules 20 to 30 and frequently appear in the shorebased paper and the practical exam.

• Rule 21 definitions: a masthead light is a white light over the fore and aft centreline showing 225 degrees (22.5 degrees abaft the beam on each side); sidelights are green on starboard and red on port, each showing 112.5 degrees; a sternlight is white showing 135 degrees; an all-round light shows 360 degrees; a towing light is yellow with the same arc as a sternlight; a flashing light flashes at 120 or more flashes per minute.
• Rule 25 (sailing vessels and vessels under oars): under 20 m a sailing yacht may use a tricolour at or near the masthead, or separate sidelights and sternlight. A tricolour is for use under sail only: it must not be used when motoring because a vessel under power must show a masthead light. A sailing vessel may in addition carry two all-round lights at the masthead, red over green, but these must not be shown together with a tricolour. A vessel under 7 m, if she cannot show these lights, must have an electric torch or lighted lantern showing a white light ready to show in time to prevent collision.
• Motor-sailing (Rule 25(e)): a vessel proceeding under sail but also being propelled by machinery shall exhibit forward where it can best be seen a conical shape, apex downwards. By night she shows the lights of a power-driven vessel.
• Rule 30 (anchored vessels and vessels aground): under 50 m, an all-round white light where it can best be seen (or by day a black ball). Under 7 m not in or near a narrow channel, fairway or anchorage, or where other vessels normally navigate, no light or shape is required. A vessel aground shows the anchor light(s) plus two all-round red lights in a vertical line (by day three balls).
• Rule 24 (towing and pushing): a power-driven vessel towing shows two masthead lights in a vertical line (three if the length of the tow exceeds 200 m), sidelights, a sternlight, a yellow towing light above the sternlight, and by day a diamond on both tug and tow if the tow exceeds 200 m. A yacht towing a dinghy a short distance does not need to show these, but a yacht being towed by a lifeboat shows normal sailing or power lights.
• Rule 23 (power-driven vessels underway): one masthead light forward, a second aft and higher if 50 m or more in length (optional below 50 m), sidelights and a sternlight. A power-driven vessel under 12 m may show an all-round white light and sidelights instead of a masthead light and sternlight.
• Rule 20: the lights prescribed shall be shown from sunset to sunrise and in restricted visibility by day. Showing your navigation lights in fog by day is a legal requirement, not an option.

Reading an unfamiliar night picture

At night, ask three questions in order:

1. What are the all-round lights, in which colours and order, telling me what the vessel is doing? (Red over red, red over white, green over white, red-white-red, white over red, three reds.)
2. Which sidelights can I see, telling me aspect? Green only: her starboard side is toward me; red only: her port side; both: she is bows-on to me; neither with white stern light: she is moving away or I am overtaking.
3. Is there a second masthead light (a large vessel: the higher one aft), and what is the angle between the two? A wide separation suggests a large vessel close by; two lights in vertical line suggest she is heading straight toward or away from me.

A vessel not under command that is making way shows sidelights and a sternlight beneath the red-over-red; if she is stopped, you see only the red-over-red lights and no sidelights. This is a deliberate trap in the RYA oral: the absence of sidelights does not always mean she is moving away.

Narrow Channels (Rule 9)

A narrow channel is any channel or fairway that a large vessel must follow because of depth or width: the main channel into Southampton Water, the approach to Harwich or the dredged channel into Poole are good examples. Rule 9 says:

1. Vessels proceeding along a narrow channel keep as near to the outer limit on their starboard side as is safe and practicable.
2. A vessel of less than 20 m in length, or a sailing vessel, shall not impede the passage of a vessel which can safely navigate only within the channel.
3. A vessel engaged in fishing shall not impede any other vessel navigating within the channel.
4. A vessel shall not cross a narrow channel if doing so impedes a vessel which can safely navigate only within it. The vessel in the channel may use five short blasts if in doubt about the crosser's intentions.
5. When nearing a bend or area where other vessels may be obscured by an intervening obstruction, sound one prolonged blast. Any approaching vessel round the bend that hears it answers with one prolonged blast.
6. Avoid anchoring in a narrow channel.

"Not impede" is different from "keep out of the way". It means acting early so that the ship never has to take action because of you. In practice: stay outside the buoyed channel where there is enough water (many yachts can run just outside the line of buoys), cross quickly and at right angles, and never sit in the channel short-tacking in front of a ship.

Overtaking in a narrow channel

Rule 13 applies regardless of anything else: the overtaking vessel keeps out of the way of the vessel being overtaken, whether you are under sail or power, until finally past and clear. In a narrow channel, overtaking may need the cooperation of the vessel ahead, so Rule 34(c) provides an agreement signal sequence:

The diagram below shows the overtaking situation and the general manoeuvring signals that any power-driven vessel in sight of another uses when it actually alters course or goes astern (Rule 34(a)).

Note that one, two and three short blasts are action signals: they describe a manoeuvre being carried out now ("I am altering my course to starboard", "to port", "I am operating astern propulsion"). They are required from power-driven vessels in sight of one another, and a yacht motoring is a power-driven vessel. Today most overtaking agreements in busy ports are made on VHF with the VTS or the ship, but you must still know the sound signals.

Local regulations

Rule 1 allows harbour authorities to make special rules. Examples you will meet: the moving prohibited zone ahead of large ships in the Solent's Thorn Channel (1000 m ahead and 100 m either side, marked by a ship flying a black cylinder or showing an all-round flashing red light, often escorted by a harbour patrol launch), and mandatory small-craft channels in ports such as Portsmouth. Always read the local notes in the almanac or pilot before entering.

Traffic Separation Schemes (Rule 10)

A TSS separates opposing streams of shipping into lanes, divided by a separation zone or line. They are found where traffic converges: the Dover Strait, off Ushant, the Casquets, Land's End, the approaches to major ports. Rule 10 applies to schemes adopted by the IMO and does not relieve any vessel of its obligations under the other rules.

Using a lane

If you are on passage along a TSS (rare for a yacht, but possible), you proceed in the appropriate lane in the general direction of traffic flow, keep clear of the separation line or zone where practicable, and normally join or leave at the termination of the lane. If you must join or leave from the side, do so at as small an angle to the general direction of traffic flow as practicable. The diagram below shows why: a shallow angle lets you merge like a car joining a motorway, so the ships in the lane see a vessel converging gradually rather than one cutting across them.

Crossing a TSS

A vessel shall so far as practicable avoid crossing traffic lanes, but if obliged to cross shall do so on a heading as nearly as practicable at right angles to the general direction of traffic flow. The important word is heading, not track. If the tide sets you down the lane, you still steer at 90 degrees to the lane and accept the resulting ground track. The reasons:

• It minimises the time spent in the lane.
• It presents a clear beam-on aspect to ships in the lane (both sidelights or none, plus your hull silhouette on radar), so they can immediately see you are crossing rather than joining.
• Ships' officers can predict your movement.

Crossing gives you no special privileges. When you meet a ship in the lane, the normal steering and sailing rules apply, but Rule 10(j) says a vessel under 20 m or a sailing vessel shall not impede the safe passage of a power-driven vessel following a traffic lane. In practice, you plan your crossing so that ships never need to alter for you. If necessary you slow down, stop, or turn to pass astern, and you then resume your right-angle heading. Under sail, if you cannot hold a reasonable speed on the correct heading, motor-sail or motor across.

Other key points of Rule 10:

• Do not enter the separation zone except when crossing, in an emergency to avoid immediate danger, or to fish within the zone.
• Avoid anchoring in a TSS or near its terminations.
• Vessels engaged in fishing shall not impede vessels following a lane.
• A vessel restricted in ability to manoeuvre while maintaining safety of navigation in a TSS (for example a buoy tender or dredger) is exempt from Rule 10 to the extent necessary.
• In the Dover Strait, the Channel Navigation Information Service (CNIS) at Dover Coastguard monitors the scheme on radar and broadcasts traffic information on VHF Ch 11. Infringements are reported and prosecuted, including those by yachts.

Inshore Traffic Zones

An Inshore Traffic Zone (ITZ) lies between the landward boundary of a TSS and the coast. Through traffic that can safely use the adjacent lane should not use the ITZ. However, vessels under 20 m, sailing vessels and vessels engaged in fishing may use the ITZ, as may any vessel en route to or from a port, offshore installation, pilot station or other place within the zone, or avoiding immediate danger.

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For a yacht on a coastal passage, the ITZ is usually exactly where you want to be: out of the shipping, and in the zone within 20 miles of a safe haven that a Coastal Skipper operates. Be aware that ITZs are also used by fishing vessels, ferries heading for local ports and other small craft, so lookout is still essential.

Conduct in Restricted Visibility (Rule 19)

Restricted visibility means any condition in which visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms or similar. Rule 19 applies to vessels not in sight of one another when navigating in or near an area of restricted visibility. Note "near": a vessel in clear weather just outside a fog bank must comply too.

The duties are:

1. Rule 19(b): 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. For a yacht, that means the engine is running and in neutral even when sailing.
2. Rule 19(c): have due regard to the circumstances and conditions when complying with Rules 4 to 10.
3. Rule 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, take avoiding action in ample time. If that action is an alteration of course, so far as possible avoid:

• an alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken;
• an alteration of course towards a vessel abeam or abaft the beam.

1. Rule 19(e): except where it has been determined that 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 a vessel forward of her beam, shall reduce her speed to the minimum at which she can be kept on course. If necessary she shall take all her way off, and in any event navigate with extreme caution until danger of collision is over.

The diagram below summarises the most important practical outcome: for a target forward of the beam, alter to starboard, not to port.

Why these particular rules?

In fog there is no stand-on or give-way vessel: both vessels have the same duty to avoid collision. If two vessels approaching nearly head-on both turn to starboard, they open out. If one turns to port and the other to starboard, they turn into each other, which is exactly what happened in several famous collisions (the Andrea Doria and Stockholm in 1956 is the classic case). The rule for vessels abeam or abaft the beam follows the same logic: turning towards them closes the range and may put you across their bow.

So the practical decision tree, when radar shows a closing target with a small or zero CPA:

In every case slowing down or stopping is lawful and gives everyone more time. For a yacht, whose radar picture may be poor and whose radar reflection may be weak, slowing down early is often the best tool you have. Make alterations bold: at least 30 to 60 degrees, so the change shows clearly on the other vessel's radar.

Sound Signals

In restricted visibility (Rule 35)

Signals are sounded at intervals of not more than 2 minutes. A short blast lasts about one second; a prolonged blast four to six seconds.

So a sailing yacht under sail alone sounds one prolonged and two short. The moment the engine goes into gear she becomes a power-driven vessel and sounds one prolonged (or two prolonged if stopped).

In sight of one another (Rules 34 and 36)

Rule 36 allows any vessel to attract attention by light or sound signals that cannot be mistaken for other signals, for example a searchlight directed at the danger (but not in a way that embarrasses another vessel's navigation).

Multi-Vessel Situations

The rules are written for two vessels. In reality you may have a ship crossing from starboard, a fishing vessel ahead and a yacht overtaking you. Work through it systematically:

1. Identify every vessel and its category (lights, shapes, AIS status, behaviour).
2. Assess risk with each one (bearing movement, radar CPA/TCPA).
3. Rank them by time to closest approach; deal with the most urgent first, but choose an action that does not create a new problem with the next.
4. Prefer actions that are good for all of them, such as slowing down to let the crossing traffic pass ahead.
5. Communicate if useful: a short VHF call on Ch 16 or 13 with the ship's name from AIS can resolve an ambiguous situation, but never let a radio conversation replace a correct manoeuvre. Agreements to pass "red to red" or "green to green" by VHF have contributed to many collisions.

Worked Example: Crossing the Dover Strait TSS

You are skipper of a 11 m yacht planning to sail from Ramsgate to Dunkirk. The route crosses the Dover Strait TSS, where the south-west-bound lane runs roughly 040/220 degrees True and the north-east-bound lane runs the same way in the opposite sense.

Planning. The two lanes and the separation zone together are roughly 10 miles wide where you will cross. The general direction of traffic flow is 040/220, so your crossing heading must be 130 or 310 degrees True. Going to Dunkirk you need 130 degrees T. At 6 knots under engine, each 4.5 mile lane takes 45 minutes.

Tide. At the time of crossing the stream is setting 050 degrees T at 2 knots. You do not steer into the tide to make good a 130 degree track. You steer 130 degrees T and accept that your ground track will be about 112 degrees T. Plan the departure and arrival waypoints at the edges of the scheme to allow for this drift, and check that the drifted track keeps you clear of lane terminations and buoys.

Execution.

1. Before entering, call Dover Coastguard (CNIS) on Ch 11 only if required; otherwise listen on Ch 11 for traffic information and keep Ch 16 on dual watch.
2. Brief the crew: lifejackets on, one dedicated lookout each side, engine running, sails set to steady the boat but not to dictate the heading.
3. On reaching the lane, steer 130 degrees T. A container ship is on your port bow at 6 miles, AIS CPA 0.2 miles ahead of you, TCPA 18 minutes. Because you must not impede, you act early: reduce speed to 3 knots. The CPA becomes 1.1 miles astern of her. Once she is clear, resume 6 knots, still heading 130 degrees.
4. In the separation zone, take a GPS fix, log it, and re-assess the next lane.
5. Repeat the process in the north-east-bound lane, where traffic now approaches from starboard.

What the examiner wants to hear. You crossed on the correct heading, did not impede, took early and substantial action, and kept a log of positions.

Worked Example: Fog in the Solent Approaches

You are motor-sailing at 5 knots towards the Needles Channel when visibility falls to 200 m. Radar shows a target bearing 010 degrees relative (just on your starboard bow) at 3 miles; after six minutes it bears 008 degrees relative at 2.4 miles. The bearing is virtually steady and the range closing: risk of collision exists.

1. Rule 19 applies. You are motor-sailing, so you are a power-driven vessel: start sounding one prolonged blast every 2 minutes or less. Engine is already running.
2. Analyse: the range closed 0.6 miles in 6 minutes, a closing speed of 6 knots. You are making 5 knots, so the target is nearly ahead and moving towards you at only about 1 knot, or is a slow vessel crossing: possibly a fishing vessel. Either way it is forward of the beam on a steady bearing.
3. Permitted action: alter boldly to starboard, say 60 degrees, or slow right down. You must not turn to port.
4. You alter 60 degrees to starboard and slow to 3 knots. Over the next 6 minutes the target's bearing draws left (moves towards your port side) and the CPA on the radar increases to over a mile.
5. You hear a single prolonged blast forward of the beam. Rule 19(e) requires you to reduce to minimum steerage speed and navigate with extreme caution until the danger is over, even though radar suggests the CPA is good.
6. Once the target passes clear astern and the range opens, resume course and speed, and log the encounter.

Worked Example: A Busy Night Passage Off Portland Bill

You are skipper of a 12 m sloop at 0100, making 5 knots under engine in the Lyme Bay approach to Portland Bill, visibility 3 miles. The tide is setting east at 2 knots. Three vessels are visible.

1. A white light with a green sidelight, bearing 030 degrees relative, steady, range 3 miles. Over 8 minutes the range falls to 2.2 miles with a steady bearing: closing speed 6 knots. You see the green sidelight and a masthead light: the vessel is crossing from starboard to port, you are the give-way vessel under Rule 15, and risk of collision exists. TCPA about 22 minutes.
2. Red over white all-round lights, bearing 300 degrees relative, range 2 miles. A fishing vessel (not trawling) is working to port; by Rule 18 you keep out of her way, and she has gear that may extend more than 150 m, shown by an extra white light in her direction.
3. A sailing yacht on the starboard bow showing a tricolour, range 1 mile, bearing drawing right. She is passing ahead and clear.

Decision. The most urgent is vessel 1. The yacht on the starboard bow limits a turn to starboard, and a turn to port would take you across the ship's bow, so instead you reduce speed to 3 knots and alter 30 degrees to starboard, accepting a small convergence with the yacht that you check by bearing; so the ship passes ahead with a CPA of about 1.5 miles. You then recheck: the bearing on vessel 1 is now moving aft, so the situation has resolved. You keep the fishing vessel's red over white to port and pass her with plenty of room; you hold your reduced speed until the yacht is clear on your starboard side.

What the examiner wants to hear. You identified each vessel from its lights, named your Rule 15 duty, used bearing movement to prove risk, acted early with a bold alteration and speed reduction, and kept a lookout on all vessels until finally past and clear.

Exam Tips: What the RYA Examiner Expects

• Name the rule. "I am the give-way vessel under Rule 15 and I will take early and substantial action under Rule 16" is better than "I'd turn".
• Say what you can see. Describe the light configuration aloud before you decide what to do.
• Show the plot or the numbers. Quote the bearing movement, CPA and TCPA when you have radar or AIS.
• Use the engine when needed. Examiners are not impressed by a skipper who tries to sail across a lane in light airs when 30 minutes of engine would make it safe.
• Lookout. Do not forget to say who is keeping the lookout and that they are not also steering or navigating.
• Local rules. Be ready to say what you would check on a pilot book before entering a major port: ship movement notices, small-craft channels, VHF channels, prohibited areas.
• Written paper. Practise recognising lights and shapes from a drawing; the shorebased paper asks you to identify vessel type, aspect and your action.

Common Mistakes

• Turning to port for a radar target ahead in fog. This is the most dangerous and most examined error. For anything forward of the beam (other than a vessel you are overtaking), turn to starboard or slow down.
• Steering a track rather than a heading across a TSS. The rule is about heading at right angles; crabbing into the tide to make good a perpendicular track presents a confusing angled aspect to ships.
• Assuming sail has priority over ships in a lane or channel. Rules 9 and 10 require sailing vessels and vessels under 20 m not to impede. "Not impede" means acting before the ship has to.
• Forgetting you are a power-driven vessel when motor-sailing. That changes your lights (masthead light on, tricolour off), your day shape (cone point down) and your fog signal.
• Small, late alterations. Ten degrees will not show on a ship's radar. Make it obvious.
• Relying on AIS alone. Many fishing vessels, small craft and warships do not transmit AIS, and AIS data can be wrong. Radar and eyes come first.
• Not sounding fog signals. It is a legal requirement and the other vessel may have no radar.
• Using VHF to arrange a passing that contradicts the rules. Use VHF to confirm intentions, not to agree non-standard manoeuvres.

Safety Notes

• Lifejackets and harnesses on in a TSS or narrow channel at night, because a collision, even a minor one, can throw crew overboard.
• Keep the engine ready when crossing shipping lanes, even if sailing.
• Pre-plan the crossing with the AIS targets on the plotter, so you know where the gaps in traffic are before you reach the lane.
• Radar reflector fitted as high as possible, and consider AIS Class B transmit as well as receive.
• Report infringements by others. If you see a ship in the wrong lane or a vessel fishing in a scheme, record the time, position and name, and tell the Coastguard or CNIS.

Summary

• Rule 18's hierarchy applies only in sight of one another, and is overridden by Rule 13 (overtaking) and qualified by Rules 9 and 10 (not impeding in channels and TSSs).
• In narrow channels keep to the starboard side, do not impede vessels confined to the channel, sound one prolonged blast at bends, and use the Rule 34(c) signals to agree an overtake.
• Cross a TSS on a heading at right angles to the traffic flow; join or leave at a small angle; use the Inshore Traffic Zone where appropriate; never enter the separation zone without reason.
• In restricted visibility there is no stand-on vessel. Proceed at safe speed with engines ready, assess radar targets carefully, alter to starboard for targets forward of the beam, never towards targets abeam or abaft, and slow down or stop when you hear a fog signal forward of the beam.
• Know the Rule 35 signals: one prolonged (power making way), two prolonged (power stopped), one prolonged and two short (sail, fishing, NUC, RAM, CBD, towing), bell for anchored, bell strokes for aground.

Check Your Understanding

1. You are under sail in a narrow channel and a large container ship is coming up astern, confined to the channel. Who keeps clear, and under which rules?

Answer: You must not impede the ship (Rule 9(b), as a sailing vessel and under 20 m), so you move to the edge of or outside the channel early. Strictly, the ship is overtaking and must keep out of your way under Rule 13, but your duty not to impede means you act first so that no risk of collision develops.

1. What heading should you steer to cross a TSS whose traffic flows 040/220 degrees T, when the tide is setting across your track?

Answer: 130 or 310 degrees T (as appropriate), a heading at right angles to the traffic flow. You accept the tidal set on your ground track rather than steering into it.

1. May a 10 m yacht on coastal passage use an Inshore Traffic Zone?

Answer: Yes. Vessels under 20 m, sailing vessels and vessels engaged in fishing may use an ITZ, as may vessels bound to or from a place within it.

1. In fog, radar shows a vessel 30 degrees on your port bow closing on a steady bearing. Which alteration is prohibited and what should you do?

Answer: An alteration to port is prohibited for a vessel forward of the beam (unless you are overtaking it). Alter boldly to starboard and/or reduce speed, and keep sounding your fog signal.

1. You hear one prolonged blast followed by two short in fog. What might it be?

Answer: A sailing vessel, a vessel engaged in fishing, NUC, RAM, CBD, or a vessel towing or pushing. You cannot tell which, so treat it with caution.

1. What fog signal does a yacht make while motor-sailing at 4 knots, and what changes if she stops the engine and sails?

Answer: Motor-sailing she is a power-driven vessel making way: one prolonged blast at intervals of not more than 2 minutes. Under sail alone she sounds one prolonged followed by two short.

1. What signals would you use to ask to overtake a ship on her port side in a narrow channel, and what is her agreement signal?

Answer: Two prolonged followed by two short. Agreement is prolonged, short, prolonged, short. If she doubts it is safe she sounds at least five short rapid blasts.

1. At night you see three red all-round lights in a vertical line above normal masthead and sidelights. What is it and what is your obligation?

Answer: A vessel constrained by her draught. You must, if circumstances permit, avoid impeding her safe passage.

1. Rule 19(e) requires what action when you hear a fog signal apparently forward of your beam?

Answer: Unless it has been determined that no risk of collision exists, 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. Can you enter the separation zone of a TSS to wait for a gap in traffic?

Answer: Generally no. You may enter the separation zone only when crossing it, in an emergency to avoid immediate danger, or to fish within it. While crossing you may adjust speed in it, but it is not a parking area.

1. A sailing yacht is stand-on in a crossing situation with a motor vessel, and it becomes clear the motor vessel is not giving way. What are the stand-on vessel's rights and duties under Rule 17?

Answer: As soon as it becomes apparent that the give-way vessel is not taking appropriate action, the stand-on vessel may take action to avoid collision by her own manoeuvre alone. If she does so in a crossing situation she should not turn to port for a vessel on her own port side. If collision cannot be avoided by the give-way vessel's action alone, she shall take whatever action best aids to avoid collision (Rule 17(b)). Sound five short blasts as a doubt signal, and act early.

1. At 1400 a ship bears 035 degrees relative at 5.0 miles and at 1412 it still bears 035 degrees at 3.8 miles. What is the closing speed and the TCPA, and what does it tell you?

Answer: The range has fallen 1.2 miles in 12 minutes, a closing speed of 6 knots. Time to reach zero range is 3.8 / 6 = 0.63 hours, about 38 minutes. A steady bearing and falling range means risk of collision exists (Rule 7). If you are the give-way vessel you must act early with a substantial alteration or speed reduction.