COLREGs

The Rules of the Road. International Regulations for Preventing Collisions at Sea.

What is the meaning of COLREGS?

COLREGs stands for International Regulations for Preventing Collisions at Sea that is published by the International Maritime Organization (IMO). It is often reffered as the “Rules of the Road” which acts as the standard guidelines for ship to follow at sea and in navigable waters to avoid ship to ship collision.

When is COLREGs adopted and entered into force?

Adopted at 1972 and came into force at July 1977.

Where does COLREGs apply?

It applies to all vessels navigating in high seas and waters connected therewith. All vessels must follow these rules.

Can local waters, ports, or rivers create a special rule over COLREGs

Yes, as long as this special rule should still match the COLREGs as closely as possible.

Can warships or fishing fleets have extra lights, shapes, or whistle signals?

Yes, government can give extra lights, shapes, or whistle signals to warships, traveling in convoys, or fishing fleet, as long as these signals can’t be mistaken to the standard navigation lights or signals.

What if a ship's unique design makes it impossible to follow every single rule?

Government can approve alternative placement of lights, shapes, or horns but it must still be closer to the rules as possible.

What is rule 1 all about?

Rule 1 establish rule that apply to all vessels navigating in high seas and connected water. It leaves room for local harbor rules, unique shaped ships, military/fishing vessels

Situation: A captain turns on all required lights and stays under the speed limit, but leaves the wheel unattended in a foggy, high-traffic area to grab a drink. The boat collides with ahead ship.

The Claim: "I followed all lighting and speed rules!"

Who’s at fault?

Captain still at fault. Under Rule 2(a), following written rules does not excuse ignoring basic common sense (like keeping a proper lookout).

Situation: Container Ship A is legally required to yield to Cargo Ship B in a crossing situation. Ship A alters course to clear behind Ship B. Suddenly, Ship B's engine fails, leaving her dead in the water directly across Ship A's bow. Sticking to standard give-way rules will cause a catastrophic collision.

The Decision: "Does Ship A stick to normal rules or make an emergency maneuver?

Break the rule immediately. Under Rule 2(b), immediate danger overrides standard steerage rules. Ship A must execute an emergency turn or reverse engines to avoid the crash.

What is rule 2 all about?

Rule 2 prevents crews from saying, "I followed the rule, so the collision isn't my fault." It emphasizes good seamanship, flexibility, and doing whatever it takes in the moment to avoid an accident.

What is a vessel according to Rule 3 (a)?

Anything that floats and moves people or goods on water—boats, ships, hovercrafts, jet skis, and even seaplanes while on the water

What is a Power-Driven Vessel according to Rule 3 (b)?

Any vessel moving by an engine or machinery

What is a Sailing Vessel according to Rule 3 (c )?

A vessel moving strictly by wind/sails. Note: If a sailboat has its engine running, it is legally treated as a power-driven vessel, even if sails are up.

What is Vessel engaged in fishing in Rule 3 (d)?

Boats using nets, lines, or trawls that limit their ability to maneuver. Trolling (towing light lines behind a boat while cruising) does not count here because it doesn't block quick steering.

What is a seaplane in Rule 3 (e)?

Any aircraft designed to operate and steer on the water surface.

What is Vessel not under command in Rule 3 (f)?

A ship that cannot steer or maneuver due to an emergency or failure (e.g., lost steering, engine failure, lost propeller). It cannot get out of the way.

What is Vessel Restricted in Her Ability to Maneuver (RAM) in Rule 3 (g)?

A ship that cannot get out of the way because of the nature of its current work

What are the activities to be consider under RAM in Rule 3 (g)?

-Laying or repairing underwater cables/pipelines 

-Dredging, surveying, or diving work

-Transferring cargo, fuel, or personnel between ships while moving

-Launching/recovering aircraft or clearing mines 

-Heavy towing operations that prevent turning easily

What is Vessel Constrained by Her Draft (CBD) in Rule 3 (h)?

A deep-draft power vessel operating in shallow or narrow channels where it cannot turn off course without running aground. 

What is Underway in Rule 3 (i)

The vessel is not anchored, not tied to a dock/shore, and not aground. If it is simply drifting with the engine off, it is still legally "underway."

What is Length and Breadth in Rule 3 (j)?

"Length" means total length from bow to stern (Length Overall / LOA); "Breadth" means the widest point of the ship.

What is In Sight of One Another in Rule 3 (k)?

Ships can actually be seen visually with the naked eye from one another (radar contact or radio contact alone does not count).

What is Restricted Visibility in Rule 3 (l)?

Any condition reducing vision on the water—fog, mist, falling snow, heavy downpours, or sandstorms.

In general, what does Rule 3 definition tells us about Collision Prevention.

In general collision rules, vessels with less control have right-of-way over vessels with more control:

NUC > RAM > CBD > Fishing > Sailing > Power-driven. 

What is
PART B: ______
Section I: _____

Part B - Steering and Sailing Rules 

Section I - Conduct of Vessels in any Condition of Visibility

What is rule 4 all about?

Application

Regardless of weather or sight, these rules always apply. Whether it is a crystal-clear sunny day, pitch-black night, thick fog, or a blinding snowstorm, every vessel must follow Rules 5 through 10 at all times.

What is rule 5 all about?

Look-out

Every vessel must continuously watch and listen using every tool available so you always know what is happening around your ship and whether you are on a collision course. 

General Rule of Rule 5: Never leave your post blind or deaf—maintain a continuous 360-degree watch using sight, hearing, and all available technology to assess collision risk before it becomes an emergency.

What is rule 6 all about?

Safe Speed

Every vessel must travel at a safe speed at all times so she can take effective action to avoid a collision and stop within a safe distance for the current conditions.

In determining a safe speed there are 6 factors to consider by all vessels, what are those?

(i) State of visibility 

(ii) Traffic density

(iii) Maneuverability of the vessel 

(iv) Nighttime background lights

(v) Environment and hazards

(vi) Vessel draft vs. water depth

In determining a safe speed there are 4 factors to consider by vessels with operational radar, what are those?

(i) Radar performance and limits: The quality, range settings, and technical limitations of your radar setup.

(ii) Range scale constraints: Limitations caused by the specific distance range scale selected on the radar display  

(iii) Environmental interference: How rain, sea clutter (rough waves), or weather obscure targets on the radar screen.  

(iv) Undetected small targets: The danger that small boats, wooden craft, ice, or floating debris might not register on radar at a safe distance.  

(v) Multi-target tracking: The total number, locations, and directions of all nearby vessels picked up by radar. 

(vi) Distance measurement: Using precise radar range measurements to assess the exact visibility around your ship.

What is Rule 6 all about?

Safe Speed
Safe speed is not a fixed number—it is any speed that allows you to take proper action to avoid a collision and stop your vessel in time for the current conditions.

What is Rule 7?

Risk of Collision

What is Rule 7a?

(a) Use every tool you have (eyes, ears, radar, AIS) to figure out if you are on a collision course. If you are unsure whether a risk exists, assume it does exist and act accordingly.

What is Rule 7b?

(b) If your ship has a working radar, use it. Scan at long ranges to spot approaching ships early, and use radar plotting (or automatic tracking like ARPA) to systematically track their path—don't just glance at the screen.

What is Rule 7c?

(c ) Never make assumptions based on incomplete or quick glimpses ("scanty" information), especially from just a quick glance at a radar screen

In Rule 7d, how can we determine if there is risk of collision?

(i) Constant bearing, decreasing range (CBDR): If the compass angle (bearing) of an approaching ship isn't changing, but the distance between you is shrinking, you will collide if no one changes course. 

(ii) Large targets or close range exception: Even if the compass angle is changing slightly, a risk of collision can still exist if you are very close, or if the approaching object is massive (like a supertanker or a long tug-and-tow), because it spans a large physical area.

What is the general rule in Rule 7?

When in doubt, assume a collision risk exists—and if an approaching vessel's compass bearing stays constant while distance decreases, you are on a collision course.

What is Rule 8?

Action to Avoid Collision

What is stated in Rule 8a?

(a) Act early and decisively: Any action you take to avoid a collision must be obvious, made early (in ample time), and follow standard rules of good seamanship. Don't wait until the last minute.

What is stated in Rule 8b?

(b) Make large, clear changes (No small tweaks): Any change in course or speed must be big enough for the other ship to clearly see with their eyes or on radar. Avoid making a series of tiny steering or speed adjustments, as they confuse the other vessel.

What is Rule 8c?

(c) Course alteration alone can be effective: If there is plenty of open water (sea room), simply changing your course—if done early and substantially—can be the best way to prevent getting too close, as long as it doesn't create a new danger with another ship nearby.

What is Rule 8d?

(d) Ensure a safe passing and verify: Your maneuver must result in passing at a safe distance. You must continuously monitor the other ship until she is completely past and clear of your vessel to make sure your action actually worked.

What is Rule 8e

(e) Slow down or stop if needed: If you need to avoid a crash—or if you just need extra time to figure out what is happening—slow down, stop completely, or reverse your engines ("take all way off").