Rule 4: Application (Any Condition of Visibility) (COLREGS)
Last reviewed October 21, 2026
The short answer
Rule 4 says the rules in Section I of the Steering and Sailing Rules, Rules 4 through 10, apply in any condition of visibility. Look-out, safe speed, risk of collision, action to avoid collision, narrow channels, and traffic separation schemes apply in clear weather, at night, and in fog alike.
The rule text
Rules in this Section apply to any condition of visibility.
International Rules, U.S. Coast Guard Navigation Rules and Regulations Handbook (NAVCEN, 2024 corrected edition), Rule 4
What it means on the water
- Covers Rules 4 to 10.
- Applies whether or not vessels are in sight of one another.
- Rules 11 to 18 apply only in sight; Rule 19 covers restricted visibility.
International vs Inland
Same in substance. Inland names the range: Rules 4 through 10.
Common exam traps
- Thinking Rule 6 safe speed only applies in fog.
- Thinking Rule 9 doesn't apply in fog.
Try 3 questions on Rule 4
Which rules apply in any condition of visibility?
- Rules 4 to 10
- Rules 11 to 18
- Rule 19 only
- Rules 20 to 31
Show answer
A. Rules 4 to 10 Rule 4.
Does Rule 5 (look-out) apply in clear weather?
- Yes
- No
Show answer
A. Yes Rule 4.
Which section applies only to vessels in sight of one another?
- Rules 4 to 10
- Rules 11 to 18
- Rules 32 to 37
- Rule 38
Show answer
B. Rules 11 to 18 Rule 11.
Frequently asked questions
What does Rule 4 cover?
It says Rules 4 to 10 apply in any condition of visibility.
Same Inland?
Yes.
Where are the in-sight rules?
Rules 11 to 18.