COLREGs: collision risk and avoiding action

Play Who Gives Way

The essentials

The COLREGs are an international framework for preventing collisions at sea. A sound answer begins with lookout and collision-risk evidence, identifies the vessels and situation, applies the relevant rules together, and chooses early, substantial, observable action when required. Labels such as stand-on and give-way never remove the duty to monitor risk or act to avoid collision.

By Richard Moore · Reviewed 2026-09-08 · independent learning guidance

Scope: This is revision, not case-specific collision-avoidance advice. Apply the complete current regulations, local rules, all available evidence and the judgement required by the actual circumstances.

What should be decided before naming a rule?

Establish visibility, the operating environment, each vessel's status and aspect, and whether risk of collision exists. A steady compass bearing can be important evidence, but close-range and restricted-visibility situations demand all available means and careful appreciation of uncertainty.

How should avoiding action be judged?

Action should be positive, made in ample time and large enough to be readily apparent, while remaining consistent with good seamanship. The safest manoeuvre depends on the full encounter, available sea room and any new risk it creates. Continue checking until the other vessel is finally past and clear.

Why are lights and shapes part of the same system?

Navigation lights and day shapes communicate vessel type, activity and aspect, which help determine which rules apply. Learn the underlying geometry rather than treating each display as a picture card. Sound signals add manoeuvring or restricted-visibility information, but they do not replace a proper lookout.

Lookout and risk assessment come before encounter labels.
Apply rules as a system, including safe speed and avoiding action.
Monitor the result until the vessels are past and clear.

Primary references used for this guide

Compass is an independent revision publisher. These maintained official, regulatory and standards-body references anchor the scope above; always check their current operational material for a real passage.

Convention on the International Regulations for Preventing Collisions at Sea
International Maritime Organization
MSN 1781 (M+F) Amendment 3: COLREGs
Maritime and Coastguard Agency

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COLREGs questions

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