Introduction
Sailing is thrilling, but the sea can be unpredictable. Every year, collisions between vessels, both large and small, occur due to misunderstanding or ignoring basic navigation rules. That’s why the International Regulations for Preventing Collisions at Sea (COLREG) exist. These rules are designed to keep sailors safe, ensure predictability and prevent accidents on open waters.
Whether you are a weekend sailor cruising the Mediterranean or a long-distance yachtsman crossing oceans, understanding COLREG is essential. In this article, we will break down these regulations into easy-to-understand terms, offer practical sailing examples and give you actionable tips to avoid collisions.
History and Purpose of COLREG
The COLREGs were developed under the authority of the International Maritime Organization (IMO) in 1972 and came into force in 1977. Before COLREG, sailors often relied on local rules or experience, which led to confusion and accidents, especially in busy shipping lanes.
The primary goal of COLREG is simple: prevent collisions at sea. By providing a universal framework, sailors and ship captains from all countries know what to expect from other vessels, no matter where they sail. Understanding these rules is not only a legal obligation but a cornerstone of responsible seamanship.
Structure of the COLREG
COLREG is organized into six main parts:
- Part A – General: Basic principles, definitions and applicability.
- Part B – Steering and Sailing Rules: Who gives way, who stands on, overtaking, head-on situations and navigation in narrow channels.
- Part C – Lights and Shapes: Visual signals for vessels, including navigation lights and daytime shapes.
- Part D – Sound and Light Signals: Rules for fog, restricted visibility and signaling maneuvers.
- Part E – Exemptions: Special cases for vessels operating under specific circumstances.
- Part F – Verification and Definitions: Clarifications and legal framework.
By breaking the rules into these parts, COLREG ensures sailors can quickly find relevant information, whether it’s about navigating a narrow channel or sailing at night.
Key Definitions Every Sailor Should Know
Understanding COLREG starts with knowing the terminology. Some essential terms include:
- Vessel: Any watercraft, including yachts, motorboats and ships.
- Power-driven vessel: A vessel propelled by machinery.
- Sailing vessel: A vessel primarily using wind for propulsion.
- Underway: Any vessel not anchored, moored, or aground.
- Restricted visibility: Conditions such as fog, heavy rain, or mist that reduce visibility.
- Stand-on vessel: The vessel that maintains course and speed in a potential collision scenario.
- Give-way vessel: The vessel that must take early and substantial action to avoid a collision.
Knowing these terms will help you interpret the rules correctly while on the water.
Rules for Safe Navigation (Part B)
1. Keeping a Proper Lookout
Always maintain a lookout by sight and hearing to make timely decisions. A sharp lookout is your first defense against collisions.
2. Safe Speed
Adjust your speed depending on traffic density, weather, visibility and your vessel’s handling. High speed reduces reaction time and increases stopping distance.
3. Risk of Collision
Use all available information — radar, AIS, visual cues — to assess whether another vessel poses a risk. If there’s any doubt, treat it as a potential collision.
4. Crossing Situations
When two power-driven vessels are crossing:
- Give-way vessel: alters course or slows down.
- Stand-on vessel: maintains course but remains vigilant.
5. Overtaking
Any vessel overtaking another must keep clear, no matter which side it approaches.
6. Head-on Situations
Both vessels should alter course to starboard to pass port-to-port.
7. Narrow Channels
Stay to the starboard side of the channel and avoid crossing if possible. Sailing vessels may have restrictions depending on wind and tides.
Lights, Shapes and Signals
Navigation Lights
- Masthead light: white light forward.
- Sidelights: red (port) and green (starboard).
- Stern light: white light aft.
- Sailing vessels may also display special lights at night.
Shapes
- Conical balls or diamonds indicate vessels restricted in maneuverability or engaged in fishing.
Sound Signals
- One short blast: “I am altering my course to starboard.”
- Two short blasts: “I am altering my course to port.”
- Prolonged blasts: signal in restricted visibility.
Practical tip for yachtsmen: Even if you rely on radar or AIS, always use visual and sound signals to communicate intentions to nearby vessels.
Rules for Restricted Visibility
Fog, heavy rain, or darkness requires extra caution:
- Reduce speed.
- Use sound signals regularly.
- Be extra vigilant about smaller vessels that may be harder to detect.
- Always consider the risk of collision and be ready to take evasive action early.
Special Considerations for Sailing Vessels
- Sailing vs power-driven vessels: Sailing vessels often have right of way unless the rules indicate otherwise.
- Wind on different tacks: Port-tack vs starboard-tack sailing vessels have defined priorities.
- Small vs large yachts: Be aware that maneuverability varies; even if you have right of way, safety comes first.
To make these rules more practical for yachtsmen, here’s a handy infographic showing who gives way in common situations, with real-world yacht examples
Infographic: Who Gives Way in Different Situations (COLREGs) – With Real Yacht Examples
| Situation | Give-way Vessel | Stand-on Vessel | Real Yacht Example |
|---|---|---|---|
| Crossing Situation (Power vs Power) | Vessel with the other on starboard side | Vessel with the other on port side | Your 35-ft sailing yacht crossing another 40-ft motor yacht; you are on port tack, other on starboard → you maintain course, motor yacht adjusts |
| Power vs Sailing | Power-driven vessel | Sailing vessel | Yacht on a starboard tack; a small motorboat approaches → motorboat must give way |
| Sailing vs Sailing (Different Tacks) | Port-tack sailing vessel | Starboard-tack sailing vessel | Two sailing yachts approaching each other; yours is on port tack → you give way to the starboard tack yacht |
| Overtaking (any type) | Overtaking vessel | Vessel being overtaken | Your yacht overtaking another slower yacht from behind → you must keep clear, alter course if necessary |
| Head-on (any type) | Both vessels alter course to starboard | Both vessels alter course to starboard | Two cruising yachts meet head-on in open water → both turn starboard to pass port-to-port safely |
| Restricted Visibility | Any vessel detecting another | N/A | Yacht sailing in morning fog, sees another yacht on AIS → reduce speed, sound horn, maintain course carefully |
| Vessels in Narrow Channels | Vessel not keeping to starboard side or crossing channel | Vessel staying on starboard side | Your yacht sailing in a marina entrance while a ferry keeps to starboard → ferry has priority, you keep clear |
| Vessels Restricted in Maneuverability | Any vessel approaching | Vessel restricted in maneuverability | Yacht passing near a dredger or a large ship performing maneuvers → yacht must give way |
Collision Avoidance in Practice
- Radar and AIS help detect vessels beyond sight, but don’t rely solely on them.
- Visual observation is crucial, especially near coasts or in crowded waters.
- Decision-making hierarchy: give way early, avoid sudden maneuvers.
- Common mistakes: assuming other vessels see you, overestimating your own maneuverability, ignoring traffic separation schemes.
Example: A yacht crossing a shipping lane should give way to a large freighter, even if technically the rules might allow otherwise.
Penalties and Legal Considerations
Violating COLREG can lead to:
- Fines and legal penalties.
- Liability in case of accidents.
- Insurance issues or claims denial.
Even if collisions are minor, it’s important to document events and report them to the authorities.
Tips for Learning and Applying COLREGs
- Keep updated with COLREG amendments.
- Make checklists for night sailing and restricted visibility situations.
- Review rules before every voyage, especially when sailing in new waters.
How to Determine the Risk of Collision at Sea (COLREG Rule: Constant Bearing, Decreasing Range)
When navigating, it’s essential to assess whether another vessel poses a risk of collision. One of the most reliable indicators is based on bearing and range:
Constant Bearing, Decreasing Range
If you observe another vessel and its bearing (angle from your bow) remains constant, but the distance between you decreases, this indicates a risk of collision.
In simple terms: the other vessel appears to stay in the same direction from your viewpoint, but it’s getting closer.
Why It Happens
This is a basic principle of relative motion. Two vessels on a collision course will appear on a fixed line of sight relative to your vessel.
If either vessel alters course or speed, the bearing will change, reducing the collision risk.
Practical Steps for Sailors
- Keep a visual lookout or use radar/AIS.
- Track the other vessel over a few minutes.
- If the bearing stays the same and range decreases: take early and substantial action (alter course or speed) as the give-way vessel, or prepare to maneuver as the stand-on vessel if applicable.
Mnemonic for Sailors
“Bearing constant, danger persistent” — a simple way to remember that a fixed bearing with decreasing distance means a potential collision.
Example:
You are sailing a 35-ft yacht on starboard tack and a 40-ft motorboat appears on your port side. Over several minutes, the boat stays in the same direction relative to your bow, but it gets closer. This signals a high risk of collision and you must take action according to COLREG.
Conclusion
COLREG is more than a set of rules; it’s a mindset for safe sailing. By understanding and practicing these regulations, yachtsmen can enjoy the thrill of sailing while minimizing risks. Proper lookout, safe speed, correct use of lights and signals and respect for right-of-way rules are the foundations of responsible seamanship. Remember, knowing the rules is one thing, but applying them consistently is what keeps you and others safe on the water.
