Rule 18: who keeps out of the way of whom.

What does COLREGs Rule 18 say?

It opens 'Except where Rules 9, 10 and 13 otherwise require', then sets out duties between vessels of different kinds. Paragraph by paragraph:

Power-driven vessel underway → keeps 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. Rule 18(a).

Sailing vessel underway → keeps out of the way of a vessel not under command, a vessel restricted in her ability to manoeuvre, and a vessel engaged in fishing. Rule 18(b).

Vessel engaged in fishing, underway → keeps out of the way, 'so far as possible', of a vessel not under command and a vessel restricted in her ability to manoeuvre. Rule 18(c).

Every vessel except one not under command or restricted in her ability to manoeuvre → avoids impeding a vessel constrained by her draught that is showing the Rule 28 signals, if the circumstances admit. Rule 18(d)(i).

Seaplane on the water → in general keeps well clear and avoids impeding; once risk of collision exists, the Part B rules apply. Rule 18(e).

WIG craft → keeps well clear and avoids impeding when taking off, landing or flying near the surface; on the water, counts as a power-driven vessel under Part B. Rule 18(f).

All of this is subject to the opening words: except where Rules 9, 10 and 13 otherwise require.

When does Rule 18 apply?

It is in Part B, Section II, so by Rule 11 it applies to vessels in sight of one another. In restricted visibility, with the other vessel not in sight, there is no order of who keeps clear of whom — Rule 19 applies, and every vessel that detects a developing close-quarters situation or risk of collision must act.

Paragraphs (a) to (c) bind vessels 'underway', which Rule 3(i) defines as not at anchor, made fast to the shore, or aground.

What about the 'pecking order' list?

The usual memory aid runs top-down: not under command, restricted in ability to manoeuvre, constrained by draught, fishing, sailing, power-driven, then seaplanes and WIG craft. It is a shorthand, not the rule's wording, and it hides what the rule says: the vessel constrained by her draught is owed 'avoid impeding', not 'keep out of the way', and only while showing the Rule 28 signals; vessels not under command or restricted in their ability to manoeuvre have no 18(d) duty at all; a fishing vessel's duty is 'so far as possible'; and the whole list yields where Rules 9, 10 and 13 otherwise require.

Is a sailing yacht with her engine on a sailing vessel?

No. Rule 3(c) defines a sailing vessel as one under sail 'provided that propelling machinery, if fitted, is not being used'. A sailing yacht motoring or motor-sailing is propelled by machinery, so she is a power-driven vessel (Rule 3(b)) and Rule 18(a) applies to her — including keeping out of the way of vessels under sail.

Is every fishing boat a 'vessel engaged in fishing'?

No. Rule 3(d) means a vessel fishing with nets, lines, trawls or other apparatus 'which restrict manoeuvrability'. It excludes a vessel fishing with trolling lines or other apparatus that does not restrict her manoeuvrability. A fishing vessel on passage to her grounds is not engaged in fishing, and nor is a yacht trolling a line astern.

What are 'not under command' and 'restricted in her ability to manoeuvre'?

Rule 3(f): a vessel not under command is one which, through some exceptional circumstance, is unable to manoeuvre as required by the rules and so cannot keep out of the way of another; in practice, a main engine or steering failure is the typical case. Rule 3(g): a vessel restricted in her ability to manoeuvre is one restricted by the nature of her work. Its list includes dredging, surveying, cable or pipeline work, replenishment underway, and a tow that severely restricts both vessels' ability to deviate from their course.

Rule 18 sets no order between the two: neither is directed to keep out of the way of the other. As we read it, both are then bound by Rule 8, by Rule 13 if one is overtaking the other, and by the ordinary practice of seamen under Rule 2.

What does Rule 18(d) say about a vessel constrained by her draught?

The protection in 18(d)(i) applies only to a vessel 'exhibiting the signals in Rule 28' — three all-round red lights in a vertical line, or a cylinder, in addition to the lights of a power-driven vessel. 18(d)(ii) puts a duty on her too: she must navigate with particular caution, having full regard to her special condition.

Only a power-driven vessel can be constrained by her draught (Rule 3(h)). The duty owed to her is a 'not impede' duty, so Rule 8(f) applies to it: take early action to leave sufficient sea room.

What do Rules 18(e) and 18(f) mean for seaplanes and WIG craft?

Both are vessels: Rule 3(a) includes seaplanes and WIG craft in the word. A seaplane — any aircraft designed to manoeuvre on the water (Rule 3(e)) — must in general keep well clear when on the water, but once risk of collision exists she follows the rules of Part B like anyone else (18(e)).

A WIG craft is a multimodal craft that, in its main operational mode, flies close to the surface using surface effect (Rule 3(m)). She keeps well clear of all other vessels when taking off, landing and flying near the surface (18(f)(i)); on the water surface she is treated under Part B as a power-driven vessel (18(f)(ii)).

What does 'Except where Rules 9, 10 and 13 otherwise require' mean?

That the Rule 18 order gives way to those three rules where they set a different duty.

Rule 13: 13(a) applies 'notwithstanding' anything in Part B, Sections I and II — any vessel overtaking another keeps out of the way of the vessel being overtaken. A sailing yacht overtaking a slow motor vessel keeps out of her way, whatever Rule 18(a) would say, until she is finally past and clear (13(d)).

Rule 9: in a narrow channel or fairway, a sailing vessel or a vessel of less than 20 metres must not impede a vessel that can safely navigate only within it (9(b)); a vessel engaged in fishing must not impede any other vessel navigating within it (9(c)); and no vessel may cross so as to impede a vessel that can safely navigate only within it (9(d)).

Rule 10: a vessel engaged in fishing must not impede any vessel following a traffic lane (10(i)), and a sailing vessel or a vessel of less than 20 metres must not impede the safe passage of a power-driven vessel following a lane (10(j)).

How do those 'not impede' duties fit with Rule 18?

Through Rule 8(f). The vessel required not to impede must take early action to leave sufficient sea room, and she is not relieved of that obligation if the two vessels come to involve risk of collision. The vessel whose passage is not to be impeded remains fully obliged to comply with the rules of Part B when risk of collision exists. So a sailing yacht crossing a channel cannot rely on Rule 18(a) to make a ship confined to that channel keep out of her way. Her own duty, from the start, is not to impede, and she keeps it even if risk of collision develops. If it does, the ship is still bound by Part B (8(f)(iii)), but by then the yacht has already failed in her own duty.

What if both vessels are the same kind?

Rule 18 does not settle it. Between two power-driven vessels, Rules 13 (overtaking), 14 (head-on) and 15 (crossing) apply. Between two sailing vessels, Rule 12 does: the vessel with the wind on the port side keeps out of the way; with the wind on the same side, the windward vessel keeps out of the way.

How might Rule 18 come up in an MCA oral?

It may come up as 'who gives way?' with a twist — the engine in gear, a channel, an overtaking. Examples of the kind of question to be ready for:

“You're on a 30-metre motor yacht. Which vessels must you keep out of the way of?”

“You're motor-sailing a yacht — sails up, engine in gear — and a vessel under sail is crossing ahead. Who keeps out of the way?”

“Your sailing yacht is overtaking a slow motor cruiser. Who keeps out of the way?”

“You're under sail, about to cross a narrow channel, and a large ship that can safely navigate only within it is approaching. Does Rule 18 make her keep out of your way?”

“Where does a vessel constrained by her draught fit in Rule 18?”

“Is a yacht trolling a line a vessel engaged in fishing?”

Where do candidates go wrong on Rule 18?

The common slips: reciting the ladder without the opening words about Rules 9, 10 and 13; saying other vessels must 'keep out of the way' of a vessel constrained by her draught; forgetting that a sailing yacht under engine is power-driven; treating any fishing boat as engaged in fishing; applying Rule 18 in restricted visibility; and dropping 'so far as possible' from 18(c).