Module 5 - COLREGs
What Are the COLREGs?
What you will learn
Run a command-level collision-avoidance sequence: establish context, build and share the traffic picture, determine risk, apply every relevant rule, then verify the outcome.
The COLREGs are a coordinated decision system, not a list of vessels with permanent right of way. A safe decision starts with context and evidence before it reaches an encounter rule.
Rule 1 applies the International Regulations for Preventing Collisions at Sea to all vessels on the high seas and in waters connected with the high seas that are navigable by seagoing vessels. Competent authorities may make conforming special rules for roadsteads, harbours, rivers, lakes and inland waterways, so charts, notices and harbour directions remain part of the passage briefing.
The current Convention contains 41 rules in Parts A–F and four Annexes. Rules 4–10 apply in any visibility; Rules 11–18 apply only when vessels are in sight of one another; and Rule 19 applies to vessels not in sight when navigating in or near restricted visibility. Seeing a radar or AIS target is not the same as being visually in sight.
At Yachtmaster level, establish safe speed and lookout, create a time-sequenced picture, decide whether risk exists, check overtaking, channel or routeing constraints before ordinary vessel responsibilities, make the required action early and monitor until finally past and clear. Rule 2 means a status signal, stand-on role, VTS message or VHF exchange never transfers the skipper's responsibility.
Look-out
Risk
Action
Responsibilities
Lights & shapes
Use the same order under pressure: context, evidence, applicable rules, clear action, verified result.
| Decision layer | Watch question | Evidence |
|---|---|---|
| Context | Are the vessels visually in sight, and what waterway rules apply? | Rules 1, 3, 4–10, 11–19 and local directions |
| Risk | What do repeated bearings, ranges and radar observations show? | Rules 5–7 and systematic observations |
| Responsibility | Is this overtaking, a channel/TSS case, or another encounter? | Rules 9, 10, 12–18 or 19 |
| Action | Is the manoeuvre early, substantial, lawful and apparent? | Rules 2, 8, 16, 17 and 19 |
| Verification | Has safe passing distance actually developed? | Continue until finally past and clear |
Brief a mixed-visibility approach
At dusk near a harbour, one ferry is visually in sight, another contact is visible only on radar inside a fog bank, and a local small-craft channel crosses the approach.
1. Separate the contacts
Record which vessel is visually observed and which is not; do not apply one encounter rule to both.
2. Add the waterway
Check the charted channel and local directions before assigning manoeuvres.
3. Make the plan observable
State the risk evidence, applicable rule, planned action, escalation trigger and how the result will be checked.
Sense check: If the briefing begins with an AIS name or 'power gives way to sail', it has skipped the context and risk evidence.
Common mistake or limitation
- COLREGs do not apply to every inland waterway in identical form; Rule 1 defines the international scope and permits conforming local special rules.
- A stand-on vessel or one not to be impeded has no licence to continue into danger.
Recap
- The current COLREGs contain Parts A–F, Rules 1–41 and four Annexes.
- Visibility, visual sight and the waterway determine the encounter framework.
- A complete decision identifies risk, applies every relevant rule and verifies the passing result.
Optional quick check
Section 1 of 14
A contact is detected on radar inside fog but is not visually seen. Which framework starts the decision?
Sources and factual review
Reviewed 2 September 2026 - Compass Revision editorial review.
Build COLREGs confidence
The full COLREGs module breaks the rules into situations, vessel responsibilities, lights, shapes, and practical quiz feedback.