International Regulations for Preventing Collisions at Sea

The International Regulations for Preventing Collisions at Sea 1972, also known as Collision Regulations, are published by the International Maritime Organization and set out, among other things, the "rules of the road" or navigation rules to be followed by ships and other vessels at sea to prevent collisions between two or more vessels. COLREG can also refer to the specific political line that divides inland waterways, which are subject to their own navigation rules, and coastal waterways which are subject to international navigation rules. They are derived from a multilateral treaty called the Convention on the International Regulations for Preventing Collisions at Sea, also known as Collision Regulations of 1960.
Although rules for navigating vessels inland may differ, the international rules specify that they should be as closely in line with the international rules as possible. In most of continental Europe, the Code Européen des Voies de la Navigation Intérieure apply. In the United States, the rules for vessels navigating inland are published alongside the international rules.

Organization of the regulatory documents

As of 2022, there are 41 Rules and four annexes in COLREGs Rules in force.

PART A - GENERAL

Rule 1 - Application. This rule states that the COLREGs should be complied with by all vessels on the "high seas".
Rule 2 – Responsibility. This rule allows Master mariners and other persons in charge of vessels to depart from the rules to "avoid immediate danger", provided there are special circumstances for doing so. The rule also effectively requires all navigators to exercise good seamanship in applying the rules.
Rule 3 – General Definitions. This rule sets out key definitions that apply to terms in the rest of the rules, including definitions for 'power-driven vessels', 'sailing vessels' and other terms such as 'not under command' and 'vessel restricted in her ability to manoeuvre.

PART B - Section I Conduct of Vessels in any Condition of Visibility

Rule 4 – Application. This rule states that the rules in this section apply to all vessels in any condition of visibility.
Rule 5 – Look-out. This rule concerns the keeping of a proper lookout to sea. It involves keeping the lookout by all available means, including audible means, visual means and by the use of marine radar.
Rule 6 – Safe Speed. This rule sets out a requirement for all vessels to proceed at a safe speed with reference to the prevailing circumstances and conditions. Relevant circumstances include, for example, the state of visibility, the presence of other ships, as well as the draught and manoeuvrability of the mariner's own ship.
Rule 7 – Risk of Collision. This rule requires all vessels to use all available means to determine if a risk of collision exists. These include the proper use of marine radar and the taking of bearings by ship's compass to determine if there is a steady bearing and risk of collision.
Rule 8 – Action to Avoid Collision. This rule sets out requirements for vessels to alter course and/or speed to pass a safe distance with other vessels. It requires alterations to be consistent with the concept of good seamanship, as well as be sufficient to be observed by the other vessel, i.e., a large and bold angle of course alteration. The rule is designed to work in operation with other rules, including Rules 16 and 17.
Rule 9 – Narrow Channels. This rule concerns those vessels keeping a course within narrow channels and fairways. It requires vessels less than 20 metres in length, fishing vessels and sailing vessels to not impede the passage of larger vessels in the narrow channel. It also gives reference to signals that can be given to allow vessels to overtake one another if following the narrow channel or fairway, as well as a separate signal when approaching a bend. Vessels are also not allowed to anchor unless there are legitimate circumstances for doing so.
Rule 10 – Traffic Separation Schemes. Typically abbreviated to TSS by mariners, these schemes aim to promote the safety of navigation by ensuring ships follow a general direction of travel within defined traffic lanes. The TSS lanes are shown on paper and electronic charts and by monitoring their position, a ship can determine their navigation within the scheme. Additionally, a TSS provides separation zones and inshore-traffic zones, to which restrictions apply. Additional restrictions also apply to some vessel types, such as fishing vessels and vessels less than 20m in length to not impede the safe passage of other/larger vessels.

PART B - Section II Conduct of Vessels in Sight of One Another

Rule 11 - Application
Rule 12 – Sailing Vessels. The rule details how two or more sailing vessels should give way to each other when meeting. This is based on the wind direction. When each sailing vessel has the wind on a different side, the vessel which has the wind on the port side should keep out of the way of the other. Alternatively when both sailing vessels have the wind on the same side, the vessel which is to windward should keep out of the way of the vessel which is to leeward. Finally, if a vessel with the wind on the port side sees a vessel to windward and cannot determine with certainty whether the other vessel has the wind on her port or starboard side, they should keep out of the way of the other, i.e. they take action to make the situation safe regardless of knowing for sure the wind situation of the other vessel.
Rule 13 – Overtaking. This rule governs overtaking situations between different vessels. The primary requirement is that for all overtaking vessels, they must keep clear of the vessels they are overtaking. For sailing vessels Rule 13 also takes precedence over rules 12 and 18 meaning the overtaking sailing vessel must keep clear.
Rule 14 – Head-on Situation. This rule requires power-driven vessels that meet head-on i.e. bow directly facing another bow, to both alter course to starboard so as to pass clear of each other. This is referred to as passing 'port to port' as the port sides separate away from each other as vessels alter. The rule effectively assigns equal responsibility to vessels to prevent collision.
Rule 15 – Crossing Situation. This rule concerns actions for vessels in crossing situations and essentially requires a vessel that has another vessel on their starboard side to stay out of the way of the other, becoming the give way vessel under rule 17. The other vessel is required to stand-on under rule 17. Also, if the circumstances of the case admit, the vessel that has the other on their starboard side should avoid crossing ahead of the other vessel.
Rule 16 – Action by Give-way Vessel. This rule requires the give-way vessel to take early and substantial action to keep well clear of the other vessel.
Rule 17 – Action by Stand-on Vessel. Rule 17 requires the stand-on vessel to maintain their course and speed. However, if it appears that the other vessel who is required to give way is not taking action, then they may take action to avoid collision according to certain requirements having been met.
Rule 18 – Responsibilities Between Vessels. Rule 18 effectively establishes an order of priority between all vessels and modes of operation of those vessels. For power-driven vessels operating normally, these types of vessels are required to keep clear of all other vessels, including sailing and fishing vessels. However, where vessels are subject to restrictions such as not under command, constrained by draft or restricted in their ability manoeuvre, then other vessels, including other power-driven vessels, sailing vessels and fishing vessels are either required to keep out of the way or not impede their passage, depending on the requirements.

PART B - Section III Conduct of Vessels in Restricted Visibility

Rule 19 – Conduct of Vessels in Restricted Visibility. This rule governs collision avoidance for vessels not in sight of another when navigating in or near an area of restricted visibility. Causes include fog, smoke and other phenomena such as heavy precipitation. The rule requires all vessels to proceed at a safe speed adapted to the conditions and to effectively take action to avoid collision in ample time. As far as possible, vessels should avoid altering to port for vessels forward of their beam unless being overtaken and avoid altering course towards a vessel abeam or abaft the beam. For ships that have heard another vessels sound signal but not observed them on radar, part e requires the ship to reduce speed to the minimum required to maintain their course and if necessary to take all way off.

PART C - Lights and Shapes

Rule 20 – Application
Rule 21 – Definitions
Rule 22 – Visibility of Lights. The minimum visible distance requirements of navigational lights are detailed under this rule. These vary according to the length of the vessel. For example, for vessels greater than 50 metres in length, the visibility ranges of lights are 6 miles for masthead lights, 3 miles for sidelights, 3 miles for the sternlight, 3 miles for towing lights and 3 miles for an all round light.
Rule 23 – Power-driven Vessels Underway
Rule 24 – Towing and Pushing
Rule 25 – Sailing Vessels Underway and Vessels Under Oars
Rule 26 – Fishing Vessels
Rule 27 – Vessels Not Under Command or Restricted in their Ability to Manoeuvre
Rule 28 – Vessels Constrained by their Draught
Rule 29 – Pilot Vessels
Rule 30 – Anchored Vessels and Vessels Aground
Rule 31 – Seaplanes

PART D - Sound and Light Signals

Rule 32 – Definitions
Rule 33 – Equipment for Sound Signals
Rule 34 – Manoeuvring and Warning Signals
Rule 35 - Sound Signals in Restricted Visibility
Rule 36 - Signals to Attract Attention
Rule 37 - Distress Signals
PART E - Exemptions
Rule 38 - Exemptions
PART F - Verification of Compliance with the Provisions of the Convention
Rule 39 - Definitions
Rule 40 - Application
Rule 41 - Verification of Compliance