Where candidates go wrong
The most common failure on this topic is treating the COLREGs as a checklist of rules rather than a system with legal force, geographic scope, and a hierarchy of principles. Examiners frequently expose this by asking about application — who is bound, where, and in what circumstances — or by presenting a scenario where rules appear to conflict. Weak candidates quote Rule 16 or Rule 18 in isolation; strong candidates explain the framework they sit within.
Legal standing and application
The International Regulations for Preventing Collisions at Sea 1972 (COLREGs), as amended, have force of law in the UK under the Merchant Shipping (Distress Signals and Prevention of Collisions) Regulations 1996. They apply to all vessels upon the high seas and all waters connected therewith navigable by seagoing vessels. This includes open ocean, estuaries, and approaches to ports — unless a competent authority has made local rules under Rule 1(b), in which case those local rules take precedence in that area and the COLREGs apply where local rules are silent.
As Master, you are personally responsible for ensuring the vessel complies at all times. Delegation to an OOW does not transfer that legal responsibility.
Structure and intent
The Rules are divided into five parts:
- Part A (Rules 1–3): Application, responsibility, definitions. Rule 2 — Responsibility — is the cornerstone: it preserves the right and duty to depart from any rule to avoid immediate danger. This is not a loophole; it is the safety valve of the entire system.
- Part B (Rules 4–19): Steering and sailing rules. Split into three sections: all conditions of visibility; vessels in sight of one another; restricted visibility. The distinction between in sight and restricted visibility is not about weather — it is about whether vessels can see each other with the naked eye.
- Part C (Rules 20–31): Lights and shapes. Lights are carried from sunset to sunrise and in restricted visibility; shapes by day.
- Part D (Rules 32–37): Sound and light signals.
- Part E (Rule 38): Exemptions for older vessels.
Key principles at Command level
Rule 2 — Responsibility demands good seamanship overrides literal rule compliance when danger is immediate. Quoting Rule 17 as justification for inaction while collision becomes inevitable is a Rule 2 failure.
Rule 5 — Lookout: every available means; this explicitly includes radar, AIS, and VHF intelligence — not eyes alone.
Rule 6 — Safe Speed: not a defined speed but a judgment using all listed factors including traffic density, manœuvrability, and visibility. The Master sets safe speed; the OOW maintains it or adjusts and records why.
Hierarchy in Part B Section II: Rule 18 gives the stand-on/give-way hierarchy across vessel categories. Candidates must know this hierarchy is conditional — it only applies where vessels are in sight of one another and where Rule 9, 10, or 13 do not override it.
Narrow channels and TSS (Rules 9 and 10) override the crossing rules of Rule 15 when both apply; examiners will test this explicitly.
Exam-critical distinction
AIS does not place vessels in sight of one another under Rule 3(k). A vessel seen only on radar or AIS is operating under restricted visibility rules (Rule 19), not Rules 13–17, regardless of actual weather conditions.