COLREGs · Rule 28
Vessels Constrained by Their Draft
A power-driven vessel constrained by her draft may exhibit three all-round red lights in a vertical line, or by day a cylinder.
What does Rule 28 actually say?#
Rule 28 is published by the IMO rather than in the public-domain federal corpus, so its verbatim wording cannot be reproduced here — there is no 33 CFR Part 83 section carrying it. The summary above states what the rule requires; the IMO publication is authoritative.
Practice this rule#
One real exam question on this rule, cited to source. No sign-up.
Under the International Rules, the term 'vessel constrained by her draft' applies only to which type of vessel?
Is there an Inland Rule 28?#
Rule 28 exists only in the international rules. There is no counterpart in 33 CFR Part 83, because the condition it addresses does not arise in the U.S. inland waters the Inland Rules govern. On the exam, an answer that applies Rule 28 to an inland scenario is wrong on that ground alone.
21 of 38 rules differ somewhere; the five the exam leans on are Rule 9, Rule 10, Rule 24, Rule 28 and Rule 34, side by side on Inland vs International Rules.
Why it shows up on the exam#
Rule 28 is worth knowing mainly for what it is not: it is permissive, it is international-only, and the vessel showing it is still a power-driven vessel. An exam answer that treats a constrained-by-draught vessel as inland, or as outranking a vessel not under command, is wrong.
What does the exam actually test here?#
The signal
Three all-round red, or a cylinder
A vessel constrained by her draught may exhibit, in addition to the lights prescribed for power-driven vessels under Rule 23, three all-round red lights in a vertical line where they can best be seen, or by day a cylinder.
It is permissive
'May', not 'shall'
Nothing obliges a qualifying vessel to display the signal, so the absence of three all-round red lights does not prove a deep-draught vessel is unconstrained.
It is international only
No Inland counterpart
There is no Inland Rule 28 and no inland 'constrained by draft' status — Inland numbering jumps from 27 to 29, and Inland Rule 18(d) is reserved where COLREGs puts the corresponding conduct provision.
Rule 28 — common exam questions#
What lights does a vessel constrained by her draught show?
Three all-round red lights in a vertical line where they can best be seen, or by day a cylinder — in addition to the lights she carries as a power-driven vessel under Rule 23. The verbatim wording is in the IMO's COLREGs text rather than the public-domain federal corpus, so it is not reproduced here.
Is a vessel required to show the constrained-by-draught signal?
No. The rule is permissive: a qualifying vessel may exhibit the lights or cylinder, and many do not.
Is there an Inland Rule 28?
No. Constrained by draft is a COLREGs-only status; the Inland Navigation Rules skip from Rule 27 to Rule 29, and Inland Rule 18(d) is reserved.
Does a constrained-by-draught vessel outrank a vessel not under command?
No. She remains a power-driven vessel in the Rule 18 order. The signal warns other vessels of her limitations; it does not move her up the pecking order.
Authoritative source#
- COLREGs Rule 28 is published by the IMO and is authoritative internationally.
Practise this rule against the real exam.
Real exam questions. No signup, no card.
Was this page helpful?