SVOP Collision Regulations and Seamanship 2 — Questions and Answers
Question 1: What lights must a vessel engaged in towing display at night when the tow exceeds 200 metres in length?
- Three masthead lights in a vertical line, sidelights, sternlight, and a towing light — plus a diamond shape by day (Correct answer)
- Two masthead lights, sidelights, and a yellow flashing light at the stern
- The same lights as a power-driven vessel underway — no special lights are required for towing
- A single white light forward and a flashing amber light at the towing post
Correct answer: Three masthead lights in a vertical line, sidelights, sternlight, and a towing light — plus a diamond shape by day
Rule 24 requires a towing vessel with a tow exceeding 200 m to show three masthead lights vertically (instead of the normal one or two), sidelights, a sternlight, and a yellow towing light above the sternlight. By day: a diamond shape where best seen on both towing and towed vessel.
Rule 24 of COLREGS specifies lights for vessels engaged in towing. The number of forward masthead lights signals the tow length: one or two = tow 200 m or under; three = tow exceeds 200 m. The towing vessel shows: three masthead lights (vertically), sidelights, sternlight, plus a yellow towing light above the sternlight. The towed vessel (or last vessel in a tow string) shows: sidelights, sternlight, and by day a diamond shape at the stern. If the tow is not alongside, no towed vessel lights differ based on tow length. These distinctive lights warn other vessels of the restricted manoeuvrability of a towing operation — both the towing vessel and tow must be given wide berth, as the combination cannot manoeuvre rapidly.
Question 2: What does Rule 2 of the Collision Regulations ('Responsibility') state about following the rules?
- It acknowledges that strict adherence to the rules does not override the need for good seamanship — operators must depart from the rules if necessary to avoid immediate danger (Correct answer)
- Rule 2 requires all vessels to follow COLREGS exactly as written with no exceptions under any circumstances
- Rule 2 permits commercial vessels to disregard lights and shapes requirements in good visibility
- Rule 2 only applies to commercial vessels over 300 GT and is not relevant to SVOP operators
Correct answer: It acknowledges that strict adherence to the rules does not override the need for good seamanship — operators must depart from the rules if necessary to avoid immediate danger
Rule 2 is the 'general prudential rule': in construing and complying with the rules, due regard shall be given to dangers of navigation and the special circumstances of the case — departures from the rules may be necessary to avoid immediate danger. This reinforces that seamanship and common sense override rigid rule-following.
Rule 2(b) is one of the most important provisions in COLREGS: 'In construing and complying with these 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 these rules necessary to avoid immediate danger.' In practice, this means a vessel that strictly follows a rule (e.g., maintaining course and speed as stand-on vessel) but causes a collision is not absolved of responsibility if good seamanship required earlier action. Conversely, a vessel that departs from a rule to avoid a collision is not necessarily in breach. Rule 2 is the ultimate backstop ensuring seamanship and prudence govern all situations — not rule-bound rigidity.
Question 3: What is the requirement for a vessel to display a 'restricted in ability to manoeuvre' (RAM) dayshape?
- A ball, diamond, and ball in a vertical line — displayed when engaged in work that limits ability to manoeuvre (dredging, laying cables, underwater ops, replenishment at sea) (Correct answer)
- Two black balls in a vertical line — same as 'not under command'
- An inverted cone only — to differentiate from a towing vessel on the same bearing
- RAM dayshapes are only required at night; no day signal is specified in the rules
Correct answer: A ball, diamond, and ball in a vertical line — displayed when engaged in work that limits ability to manoeuvre (dredging, laying cables, underwater ops, replenishment at sea)
A vessel restricted in ability to manoeuvre displays ball-diamond-ball in a vertical line by day. This indicates it is engaged in work (dredging, surveying, mineclearance, dive support, replenishment at sea) that limits its ability to deviate from course, so other vessels must give it wide berth.
Rule 27 covers vessels not under command (NUC) and vessels restricted in ability to manoeuvre (RAM). A RAM vessel displays: two all-round red lights vertically (night) or two black balls vertically (NUC), while a RAM vessel specifically shows ball-diamond-ball vertically (day) and red-white-red lights vertically (night). RAM vessels include: vessels laying, servicing, or picking up submarine cables; vessels engaged in dredging, surveying, or underwater operations; vessels engaged in replenishment at sea; vessels engaged in launching or recovering aircraft; and vessels engaged in minesweeping. All other vessels (except NUC) must keep out of the way of a RAM vessel. The wide berth required acknowledges that the RAM vessel physically cannot alter course without compromising the safety of its operation.
Question 4: When two vessels are meeting head-on in a narrow channel and there is not enough room to pass, what should they do?
- Both vessels should communicate via VHF, agree on a passing arrangement, and the vessel with most sea room or easiest manoeuvring should back down first (Correct answer)
- The vessel proceeding upstream (against the current) always has right of way and the other must reverse
- The give-way vessel determined by COLREGS crossing rules must immediately stop engines
- Both vessels should anchor simultaneously and wait for a Vessel Traffic Service ruling
Correct answer: Both vessels should communicate via VHF, agree on a passing arrangement, and the vessel with most sea room or easiest manoeuvring should back down first
When meeting in a narrow channel with insufficient room to pass safely, both operators should communicate on VHF (Ch 16 or the working channel), agree on the safest arrangement, and the vessel with more sea room or easier manoeuvrability should back down to allow the other to proceed.
Head-on meeting in a narrow channel is a common pilotage situation requiring cooperation rather than strict application of rules. Rule 9 establishes starboard-side keeping but does not address what to do when the channel is too narrow for both to proceed simultaneously. Good seamanship and the 'responsibility rule' (Rule 2) require: (1) Early recognition of the situation — not waiting until meeting at close quarters; (2) VHF communication to agree on a passing arrangement; (3) The vessel with most room, easiest astern manoeuvring, or that has reached a wide spot first backs down to allow the other to pass; (4) Anchor in a wide spot if necessary; (5) The vessel proceeding with the flood tide in tidal channels traditionally has right of way, though this varies locally. Local knowledge and good communication are essential.
Question 5: What does the term 'give way early and substantially' mean in practice?
- Make a large, clearly visible course or speed change while there is still plenty of room — not a small tweak at the last moment (Correct answer)
- Signal your intention to give way by sounding one short blast before altering course
- Slow to bare steerageway as soon as you identify the stand-on vessel
- Call the stand-on vessel on VHF to confirm your intentions before altering course
Correct answer: Make a large, clearly visible course or speed change while there is still plenty of room — not a small tweak at the last moment
Rule 16 requires that the give-way vessel's action be early (with plenty of time and space remaining) and substantial (a course change of 30° or more, or a large speed reduction) so that the stand-on vessel can clearly see and confirm that avoiding action is being taken.
The phrase 'early and substantial' in Rule 16 has specific practical meaning: 'Early' means the action must be taken with enough time remaining that the stand-on vessel can observe it and confirm it is effective, and so that further action is possible if the initial manoeuvre proves insufficient. At vessel speeds, this may mean acting when ranges are still 1–3 nautical miles depending on speed and conditions. 'Substantial' means a course alteration of 30°, 45°, or more — not 5° or 10° which would be invisible to the stand-on vessel from a distance. A substantial speed reduction (to near stop) is also acceptable. Small, late course changes are not only ineffective — they are dangerous because the stand-on vessel may not notice them in time to respond if they fail.
Question 6: What is 'compass deviation' and how is it determined for a vessel?
- The error in the compass caused by the vessel's own magnetic field — determined by swinging the vessel on known headings and comparing compass readings to magnetic bearings (Correct answer)
- The annual change in magnetic variation recorded on Admiralty charts
- The difference between true and magnetic north at a given location
- The error introduced by electrical interference from the vessel's radio equipment
Correct answer: The error in the compass caused by the vessel's own magnetic field — determined by swinging the vessel on known headings and comparing compass readings to magnetic bearings
Deviation is the error in the compass caused by the magnetic influence of the vessel's own iron, steel, and electrical systems. It varies with heading. It is determined by 'swinging the compass' — comparing compass readings against known magnetic bearings on multiple headings — and recorded on a deviation card.
Every ferrous vessel creates its own magnetic field that distorts the compass. Deviation is the angle between magnetic north and compass north, caused by the vessel's own magnetism. It varies by heading — typically ranging from 0° to ±20° on different courses. To determine deviation: (1) Take the vessel to an area with a known transit or bearing; (2) Slowly turn through all 360° of heading (swing the compass); (3) On each heading, read the compass and compare to the known magnetic bearing — the difference is deviation for that heading; (4) Record the results on a deviation card (or table) posted at the helm; (5) The formula TVMDC (True + Variation = Magnetic; Magnetic + Deviation = Compass) is used for course conversions. Deviation must be re-checked after major structural changes, new engine installation, or changes in electronics.
SVOP Collision Regulations and Seamanship 2
What lights must a vessel engaged in towing display at night when the tow exceeds 200 metres in length?