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COLREGs

What is the safest response if CPA is uncertain in fog?

Short answer

Reduce speed or take way off as appropriate while assessing

Unclear CPA is a time-and-margin problem. Slow or take way off as appropriate while systematic observations mature. Revisit Rule 19 Thinking.

Sources and scope

Reviewed by Richard Moore on . This answer is scoped to international collision-avoidance and small-craft radar practice; check the current chart, publication, local rules and official operational guidance before acting afloat.

Quick check

What is the safest response if CPA is uncertain in fog?