When can a course change alone be most effective?

With sufficient sea room, timely and substantial

Rule 8: Action to Avoid Collision (COLREGS)

Last reviewed October 21, 2026

The short answer

Rule 8 says action to avoid collision must be positive, made in ample time, and with good seamanship. Course or speed changes should be large enough to be readily apparent, avoiding a series of small changes. The action should result in passing at a safe distance, checked until the other vessel is finally past and clear.

The rule text

be positive, made in ample time and with due regard to the observance of good seamanship.
International Rules, U.S. Coast Guard Navigation Rules and Regulations Handbook (NAVCEN, 2024 corrected edition), Rule 8

a succession of small alterations of course and/or speed should be avoided.
International Rules, U.S. Coast Guard Navigation Rules and Regulations Handbook (NAVCEN, 2024 corrected edition), Rule 8

What it means on the water

Positive, ample time, good seamanship (8(a)).
Large enough to be readily apparent visually or by radar (8(b)).
With sea room, a course change alone may be most effective, if timely, substantial, and not creating another close-quarters situation (8(c)).
Pass at a safe distance and keep checking (8(d)). Slow, stop, or reverse if needed (8(e)).
A vessel required not to impede must act early to leave sea room, and remains obliged even when risk of collision develops (8(f)).

International vs Inland

Same in substance. Inland refers to Subpart B (Rules 4 to 19) where International says this Part.

Common exam traps

Choosing several small turns over one bold turn.
Forgetting that slowing or stopping is a valid action (8(e)).

Try 3 questions on Rule 8

Rule 8 says avoiding action should be:
1. Small and gradual
2. Positive and in ample time
3. Only by speed
4. Only after signals
Show answer
B. Positive and in ample time Rule 8(a).
What should be avoided?
1. A large course change
2. A succession of small alterations
3. Slowing down
4. Stopping
Show answer
B. A succession of small alterations Rule 8(b).
When can a course change alone be most effective?
1. Always
2. With sufficient sea room, timely and substantial
3. Never
4. Only in fog
Show answer
B. With sufficient sea room, timely and substantial Rule 8(c).

Frequently asked questions

What makes avoiding action correct under Rule 8?

Positive, in ample time, large enough to be readily apparent, and resulting in passing at a safe distance.