COLREGs : International Regulations for Preventing Collisions at Sea

Colregs: International regulations for preventing collisions at sea 1972 are a set of rules published by the IMO (International maritime organization) to prevent collisions at sea. Colreg 1972 is the final stage of rules agreed upon a convention in London in 1972.

Surely one of the most important innovations adopted in 1972 was the introduction of the traffic separation scheme, analyzed in the details in RULE 10, where it indicated all the requirements that a power-driven vessel and vessels must adopt during their transit. 

The COLREGs are divided into 41 rules, each being part of a specific part. Part A – General; Part B – Steering and Sailing; Part C – Lights and Shapes; Part D – Sound and Light signals; Part E – Exemptions; and Part F – Verifying compliance with the provisions of the Convention. In the remaining part of the conventions, we find the annexes that detail the characteristics of the lights and shape, their positioning, and sound signaling appliance.

Part A (General Rule 1-3)

Colregs part A contains the general provision of the Convention and the correct way to interpret and use the Colreg. It is part of part A of Colreg, the rule 1,2,3 that respectively indicate the applications, responsibilities, and definitions.

Part B Steering and Sailing (Rules 4-19)

Part B of COLREGs is divided into two parts: Section 1 applies to any visibility conditions. Section II – Conduct of vessels in sight of one another (Rules 11-18), and Section III – Conduct vessels in restricted visibility (Rule 19).

Section I – Conduct of vessels in any condition of visibility (Rules 4-10)

Section II – Conduct of vessels in sight of one another (Rules 11-18)

Section III – conduct of vessels in restricted visibility (Rule 19)

Part C Lights and Shapes (Rules 20-31)

Part C of the Colreg convention describes the requirements of lights and daily shapes that a ship must carry on to be detected properly by other ships and shows her current navigation status. 

Part D Sound and Light Signals (Rules 32-37)

Part D of Colreg is particularly important during restricted visibility. All the rules listed in part D of the Colreg deal with sounds and light signals.

Part E Exemptions (Rule 38)

Part E of Colregs contains only one rule, and it is related to the exemptions.

Part F Verification of compliance with the provisions of the Convention

Part F of Colregs is the last part of the Colregs Convention. Part F of Colregs was introduced with an amendment on the 1st of January 2016, IMO Resolution A.1085(28).


  • Annex I – Positioning and technical details of lights and shapes
  • Annex II – Additional signals for fishing vessels fishing in close proximity
  • Annex III – Technical details of sounds signal appliances
  • Annex IV – Distress signals, which lists the signals indicating distress and need of assistance.