IALACOLREG
18

Responsibilities Between Vessels

Rule 18 sets the basic responsibilities between vessel types. Constrained-by-draught vessels receive special consideration but are not simply another rung in a fixed hierarchy.

Rule 18 establishes the responsibilities between different vessel types.

a
A power-driven vessel underway shall keep out of the way of: a vessel not under command (NUC), a vessel restricted in her ability to manoeuvre (RAM), a vessel engaged in fishing, and a sailing vessel.
b
A sailing vessel underway 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.
c
A vessel engaged in fishing 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.
d
Any vessel other than a vessel not under command or restricted in her ability to manoeuvre shall, if circumstances admit, avoid impeding the safe passage of a vessel constrained by her draught and displaying the signals prescribed in Rule 28. The constrained-by-draught vessel must still navigate with particular caution.
e
A seaplane, and any WIG craft operating near the surface, should in general keep well clear of all vessels and avoid impeding their navigation. When risk of collision exists, they must comply with the Rules as far as possible.

A practical memory aid is: NUC before RAM, then fishing, then sailing, then power-driven. Keep in mind that overtaking, narrow-channel and restricted-visibility rules may still control the actual manoeuvre.

STCW Bridge Watch Lens

1

Decide applicability before manoeuvring: Rules 4-10 apply in any visibility, Rules 11-18 only when vessels are in sight, and Rule 19 governs radar-only encounters in restricted visibility.

2

Build the traffic picture with sight, hearing, radar/ARPA and chart context. Do not let AIS or one isolated bearing replace systematic observation.

3

After manoeuvring, keep monitoring bearing, range, CPA/TCPA and passing distance until the other vessel is finally past and clear.

Exam Focus

1

Identify the vessel types first, then the relative bearing, then whether one vessel is overtaking. Misclassifying the encounter is the usual exam failure.

2

If two rules seem to conflict, check the order carefully: overtaking duties still apply, and Rule 2 still requires ordinary seamanship.

Key Takeaways

1

Rule 18 is about responsibilities between vessel classes, not a magic answer that replaces the rest of COLREG

2

Constrained-by-draught vessels are given special consideration through the 'shall not impede' wording

3

Power-driven vessels generally carry the broadest give-way burden

4

Overtaking and other more specific rules can still govern the situation

Common Mistakes

Treating constrained-by-draught as if it automatically overrides every other rule

Forgetting that the stand-on/give-way analysis still depends on the actual encounter and not just vessel labels

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