Collision Regulations (COLREGS)

Updated 11 Oct 2019

Ship Radar

From a safety perspective, navigating a ship is as much about avoiding hazards as it is about getting from A to B. To achieve this requires knowledge of physical hazards such as rocks, sandbanks, wrecks, exclusion zones and the like which will need to be avoided during the voyage; weather and tidal conditions likely to be encountered and the actions of other ships.

Knowledge of physical hazards comes from proper interpretation of navigational charts and notices to mariners, tidal and weather conditions and some other transient events will be advised by way of tide tables, weather reports and Maritime Safety Information broadcasts, some of which are part of GMDSS and some of which may be subscriber services by commercial organisations. Being aware of other ships is a combination of using the senses of sight and sound to see and hear other vessels and using equipment such as radar and AIS. Radar and Sonar are also used to detect objects other than ships above and below the water.

Collision Regulations

When underway, ships are obliged to follow a set of rules that are formalised in the Convention on the International Regulations for Preventing Collisions at Sea, 1972, which became effective on 15 July 1977. The rules (commonly called 72 COLREGs) are part of the Convention, and vessels flying the flags of states ratifying the treaty are bound by the rules.

The regulations are notable in themselves given that they have their roots in the 19th century and represent a much older international co-operation on maritime matters than SOLAS or the IMO although they now come under the umbrella of both.

Initially devised in the age of sail when collisions between vessels most often resulted from the variability of the wind and the inability of ships to change course rapidly, the ‘rules of the road’ have been revised over time taking account of technology advances and the advent of powered vessels.

In November 1981, IMO’s Assembly adopted 55 amendments to the 72 COLREGs which became effective on 1 June 1983. The IMO also adopted nine more amendments that became effective on 19 November 1989 and subsequent amendments at different dates since. The rules were consolidated in 2003 but further minor amendments have been made that are circulated as supplements.

The COLREGs include 41 rules divided into six sections: 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 - Verification of compliance with the provisions of the Convention. There are also four Annexes containing technical requirements concerning lights and shapes and their positioning; sound signalling appliances; additional signals for fishing vessels when operating in close proximity, and international distress signals.

Although STCW requires navigators to be fully conversant with COLREGs, a failing in this respect is frequently mentioned in official marine accident investigations. The possible advent of autonomous ships and how they will be able to respond as COLREGs demands is an issue that is currently on the agenda of the IMO’s MSC committee.

While COLREGs sets the accepted international requirements, port states and other local authorities can permit deviations from them although these must be notified by way of Notices to Mariners.

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