COLREGs · Rule 4 · 33 CFR §83.04
Application
Rules in Section I apply in any condition of visibility. This includes Rules 5–10 (look-out, safe speed, collision risk, avoidance action, narrow channels, traffic schemes).
What does Rule 4 actually say?#
Source
Practice this rule#
One real exam question on this rule, cited to source. No sign-up.
Rules 11 through 18 of the Inland Navigation Rules apply only when which condition is met?
Does Inland Rule 4 change anything?#
Inland Rule 4 is 33 CFR §83.04, reproduced above, and carries no exam-relevant divergence from COLREGs Rule 4. One answer serves both the International and the Inland version of a Rules of the Road question on this rule — which is worth knowing precisely because several neighbouring rules do not work that way.
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 4 is a one-line scoping rule, and its whole exam value is the boundary it draws: Rules 5 through 10 apply in any condition of visibility, while Rules 11–18 need the vessels to be in sight of one another and Rule 19 governs when they are not.
What does the exam actually test here?#
What it covers
Rules 4 through 10
Look-out, safe speed, risk of collision, action to avoid collision, narrow channels, and traffic separation schemes. These duties never switch off.
The test
Any condition of visibility
Clear day, fog, snow, night — it makes no difference to Rules 5–10. There is no visibility threshold below or above which they stop applying.
The contrast
Sections II and III are conditional
Rules 11–18 apply only to vessels in sight of one another; Rule 19 applies only in or near an area of restricted visibility. Rule 4 exists to make clear that Section I is not conditional in either way.
Rule 4 — common exam questions#
What does Rule 4 do?
It states that Rules 4 through 10 apply in any condition of visibility (33 CFR §83.04).
Do the look-out and safe-speed rules apply in clear weather?
Yes. Rules 5 and 6 sit inside the Rule 4 block, so they apply in any condition of visibility — a proper look-out and a safe speed are required on a clear day just as in fog.
Which rules do not apply in fog?
Rules 11 through 18 apply only to vessels in sight of one another, so they do not govern an encounter where the vessels cannot see each other. Rule 19 governs instead.
Authoritative source#
- 33 CFR §83.04 — this section with its neighbours. 33 CFR Part 83 is public domain; checked 2026-05-16.
- COLREGs Rule 4 is published by the IMO and is authoritative internationally.
Practise this rule against the real exam.
Real exam questions. No signup, no card.
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