Quick Summary
The COLREGS, short for Convention on the International Regulations for Preventing Collisions at Sea, define how vessels should navigate to avoid collisions. They govern responsibilities between ships, steering and sailing rules, lights, shapes, and sound signals essential for safe navigation.
Introduction
Every mariner, whether a cadet on their first voyage or a master with decades of experience, must know the COLREGS. These rules keep order on the open sea, where no traffic lights guide the way and no road markings divide the lanes. The ocean may seem wide and empty, but in narrow channels, crowded approaches, or poor visibility, the lives of crew and the safety of vessels depend on every navigator understanding their responsibilities.
COLREGS are the closest thing the sea has to a universal language. Learn them well and you gain the confidence to interpret any situation — who must give way, who must maintain course, and what actions prevent collisions.
The Purpose of the COLREGS
The COLREGS exist for one reason: to prevent collisions. They do this by defining responsibilities between vessels, creating predictable behavior, and ensuring that all mariners follow the same rules no matter where they sail. The rules cover every aspect of collision avoidance:
- How vessels should act when meeting, crossing, or overtaking
- What lights and shapes vessels must display
- What sound and light signals should be used
- How to navigate in restricted visibility
- The general conduct expected of watchkeepers
The key is consistency. When every vessel behaves according to the COLREGS, uncertainty fades, and safe navigation becomes possible even in challenging waters.
General Responsibilities (Rules 1–3)
The first rules clarify how COLREGS apply. They make it clear that the rules govern all vessels on the high seas and in connected waters. Watchkeepers must maintain a proper lookout at all times, using sight, hearing, and all available means. In practice, this means radar, AIS, and electronic charts should support — not replace — the human eye.
The rules also emphasize that every mariner has a duty to avoid collision, even if strict adherence to another rule might not prevent danger. Common sense and good seamanship always supplement the written rules.
Conduct of Vessels in Any Condition of Visibility (Rules 4–10)
Before vessels meet, cross, or maneuver, the COLREGS first establish how every ship must behave in all conditions — day or night, clear weather or fog. These rules form the foundation of safe navigation. They emphasize awareness, caution, and consistency, ensuring that every mariner acts with the same discipline regardless of what the sea or sky is doing.
Lookout (Rule 5)
A proper lookout is the foundation of every safe watch. It means scanning the horizon, listening for signals, monitoring instruments, and staying aware of both traffic and the environment.
Safe Speed (Rule 6)
A vessel must travel at a speed that allows it to take proper and effective action to avoid collision. Conditions matter — darkness, traffic, weather, and maneuverability all influence what is considered “safe.”
Risk of Collision (Rule 7)
If there is any doubt about a risk of collision, you must assume risk exists. Even a small change in bearing or range can signal danger.
Action to Avoid Collision (Rule 8)
When action becomes necessary, it must be positive and taken in good time. Small, hesitant alterations create confusion; bold, obvious maneuvers communicate intent.
Narrow Channels (Rule 9)
In channels, vessels must keep as near to the starboard side as is safe and practical. Larger vessels restricted by their draft have priority.
Traffic Separation Schemes (Rule 10)
Vessels must follow the general flow of traffic, avoid crossing lanes if possible, and remain aware of separation zones. Small craft should avoid impeding large vessels.
Steering and Sailing Rules (Rules 11–18)
These rules form the heart of collision avoidance. They explain how vessels interact when they meet.
Meeting Head-On (Rule 14)
Two vessels meeting head-on should both alter course to starboard, passing port side to port side. This predictable behavior prevents hesitation.
Crossing Situations (Rule 15)
When two vessels cross, the vessel with the other on her starboard side must give way. The stand-on vessel maintains course and speed until the give-way vessel’s actions are clear.
Overtaking (Rule 13)
A vessel overtaking another must keep clear until safely past and out of danger. The overtaken vessel remains the stand-on vessel.
Responsibilities Between Different Vessels (Rule 18)
Not all ships maneuver equally. A power-driven vessel should keep clear of:
- A vessel not under command
- A vessel restricted in ability to maneuver
- A vessel engaged in fishing
- A sailing vessel
This hierarchy reflects physical limitations at sea.
Lights and Shapes (Rules 20–31)
Lights and shapes allow vessels to communicate their status and movement even when visibility is limited. At night or in busy waters, these signals become the mariner’s language, helping watchkeepers identify other ships long before they are close enough to speak or maneuver. Understanding them is essential for safe navigation and collision avoidance.
Navigation Lights
Lights tell other vessels who you are, what you’re doing, and how you’re moving. At night or in restricted visibility, lights are your language.
A mariner learns to identify:
- Masthead lights
- Sidelights
- Stern lights
- Towing lights
- Special lights for fishing, towing, dredging, pilotage, and restricted maneuvering
Day Shapes
Shapes communicate vessel status during daylight. Three common examples:
- Ball: anchored or vessel aground (with additional shapes)
- Cone apex down: sailing vessel using engines
- Ball-diamond-ball: vessel restricted in ability to maneuver
Knowing these shapes helps you assess situations long before vessels are close.
Sound and Light Signals (Rules 32–37)
Navigation isn’t always visual. Fog, rain, darkness, or distance can make lights and shapes difficult to see. Sound signals — short blasts and long blasts — communicate intent and position.
Examples include:
- One short blast: altering course to starboard
- Two short blasts: altering course to port
- Three short blasts: operating astern propulsion
- One long blast: warning or making position known in fog
Signals differ by situation, but the principle remains the same: communication prevents confusion.
Conduct in Restricted Visibility (Rule 19)
Fog and heavy weather limit sight and create the most unpredictable conditions at sea. In these moments, COLREGS take on an even greater significance.
A vessel must:
- Proceed at a safe speed for the conditions
- Use radar and AIS to supplement watchkeeping
- Listen carefully for signals from other vessels
- Be prepared to take immediate avoiding action if risk appears
Experienced mariners know that fog demands respect. Even with modern equipment, overconfidence leads to danger.
The Spirit of the Rules: Good Seamanship
COLREGS are not a checklist. They rely on judgment, awareness, and the willingness to act decisively when needed. A skilled navigator understands not only what the rules say, but why they exist. Most collisions occur not from ignorance but from hesitation, poor lookout, or misinterpretation.
A mariner who follows the rules — and understands their purpose — becomes predictable, competent, and trusted on the bridge.
Conclusion
COLREGS form the backbone of safe navigation. They guide vessels through crowded channels, open seas, and difficult weather. For new seafarers, learning these rules is as important as learning the ship itself. With practice, they become second nature — a steady framework for every decision taken on watch.
Fair winds as you prepare for the day when the bridge is yours and your judgment keeps the ship safe.
