Navigation Rules and COLREGS Refresher: A Comprehensive Guide for Safer Seas

Refresh your understanding of maritime navigation rules and COLREGS. This comprehensive guide explores their importance, real-world scenarios, and key updates for modern shipping.

Why Navigation Rules and COLREGS Matter in Modern Maritime Operations

The sea may be vast, but collisions still happen. In fact, human error—particularly navigational mistakes—remains one of the leading causes of maritime accidents, according to the Marine Accident Investigation Branch (MAIB) and IMO safety statistics. This is where the International Regulations for Preventing Collisions at Sea (COLREGs) come into play. Designed to act as the maritime equivalent of road traffic laws, COLREGs serve as the international rulebook for preventing collisions between vessels. First adopted by the International Maritime Organization (IMO) in 1972, these rules remain as vital today as ever, especially with growing vessel traffic, autonomous ship trials, and evolving bridge technologies.

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The International Regulations for Preventing Collisions at Sea (COLREGs): An Overview

For maritime students, cadets, and ship officers, the COLREGs are not merely a set of rules to be memorized for an exam; they are the foundational legal and operational framework for safe navigation. Mastery of the COLREGs is a critical component of professional competence, directly impacting the safety of life, the protection of the marine environment, and the security of multi-million dollar assets.

Credit: MySeatime

The 41 rules are systematically organized into five parts, each addressing a crucial aspect of collision avoidance.

Breakdown of the COLREGs Structure:

Part A – General (Rules 1-3)

• Purpose: Establishes the scope, application, and overarching responsibility.

• Key Professional Focus:

  • Rule 1 (Application): Clarifies that the rules apply to all vessels upon the high seas and all waters connected thereto. Understanding where the rules are legally paramount versus where local inland rules might take precedence (e.g., US Inland Rules) is vital for officers.

  • Rule 2 (Responsibility): Perhaps the most important rule. It states that no rule exonerates any vessel from the consequences of neglecting any precaution required by “the ordinary practice of seamen” or by “special circumstances.” This is the “catch-all” safety rule, emphasizing that professional judgment and seamanship always trump strict legal interpretation. A right-of-way vessel must still take action if the give-way vessel is not taking appropriate action.

  • Rule 3 (General Definitions): Provides precise legal definitions for terms like “vessel,” “power-driven vessel,” “vessel not under command,” etc. Misinterpreting a definition can lead to a catastrophic misapplication of the rules.

Part B – Steering and Sailing Rules (Rules 4-19)

• Purpose: The “how-to” of collision avoidance, covering conduct in any condition of visibility and specific encounter scenarios.

• Key Professional Focus: This is the core of practical watchkeeping. It is subdivided into three sections:

  1. Conduct in Any Condition of Visibility (Rules 4-10): The fundamental principles that must be applied constantly.

  2. Conduct of Vessels in Sight of One Another (Rules 11-18): Rules for specific encounter scenarios (head-on, crossing, overtaking).

  3. Conduct in Restricted Visibility (Rule 19): Special procedures for navigating in or near fog, mist, or heavy precipitation, where vessels are not in sight.

Part C – Lights and Shapes (Rules 20-31)

• Purpose: Standardizes the lights (for night and poor visibility) and shapes (for day) that vessels must exhibit to convey their status, size, and activity.

• Key Professional Focus: This is the “language” of navigation. Correct identification of a vessel’s lights is the primary method for assessing a situation at night. Officers must be able to instantly recognize, for example, the difference between a towing vessel, a vessel constrained by her draught, and a fishing vessel, as their rights and responsibilities differ significantly.

Part D – Sound and Light Signals (Rules 32-37)

• Purpose: Governs the use of sound signals (whistles, fog horns) and light signals (flashing lights) to indicate maneuver, intention, or warn of presence in restricted visibility.

• Key Professional Focus: Proficiency in sound signals is critical for restricted visibility procedures. Misinterpretation of a whistle signal can be the direct cause of a collision.

Part E – Exemptions (Rules 38-41)

• Purpose: Addresses vessels built or retrofitted before the rules were adopted, granting them certain exemptions.

 

Core Rules for Daily Watchkeeping: Beyond Memorization

While all rules are important, these are the pillars of daily bridge resource management (BRM). Understanding the “why” behind them is essential.

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Integration into Professional Training and Practice

These rules are rigorously embedded in STCW (Standards of Training, Certification and Watchkeeping) courses, from Officer in Charge of a Navigational Watch (OICNW) up to Master level. Proficiency is assessed through:

• Theoretical examinations.

• Simulator-based assessments (BRM and Ship Handling simulators), where complex multi-vessel scenarios test the application of all rules under pressure.

• Practical onboard assessment during cadet sea time and officer rotations.

For the professional mariner, the COLREGs are a living document. Their correct application, combined with sound judgment and unwavering seamanship as mandated by Rule 2, is what defines a competent and safe officer on the watch.

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Key Developments and Technological Adaptations

With the rise of smart ships, autonomous navigation systems, and integrated bridge systems, questions are being raised about how traditional COLREGs are implemented.

Automation and COLREGs Compliance

Companies like Wärtsilä and Kongsberg are developing autonomous vessel systems capable of interpreting COLREG rules using AI and sensor fusion. For instance, Yara Birkeland, the world’s first fully electric autonomous container ship, is designed to comply with COLREGs without human input. However, these systems are still being tested, and IMO discussions are ongoing about revising COLREGs to address automation.

E-Navigation Support Tools

Modern Electronic Chart Display and Information Systems (ECDIS), ARPA radars, and AIS now include risk-of-collision alerts. Some systems even recommend maneuvers. However, relying too heavily on tech can dull a mariner’s practical understanding, so training and refresher guides remain essential.

According to the UK Maritime and Coastguard Agency (MCA), navigational accidents in coastal waters are often due to improper use or overreliance on these tools.

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Real-World Scenarios and Case Studies

Case Study: MV ACX Crystal and USS Fitzgerald (2017)

This tragic collision off the coast of Japan claimed the lives of seven sailors. Investigations pointed to failure in watchkeeping, confusion in right-of-way rules, and poor situational awareness—all violations of COLREGs.

Case Study: Ever Given in the Suez Canal (2021)

While not a direct result of rule violation, the grounding of Ever Given reminded the world how vital navigation practices are in constrained waterways. It reignited discussion about COLREG Rule 9 (Narrow Channels) and the role of tugs and pilots.

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Challenges and Common Pitfalls

Despite formal training, mariners often fall into common traps:

• Overconfidence in electronics: Watchkeepers may trust ECDIS over visual confirmation, violating Rule 5.
• Language barriers and multicultural bridges: Miscommunication between crew can delay or misinterpret Rule 8 actions.
• Fatigue: Especially in short-sea shipping and watch rotations, fatigue leads to lapses in Rules 5 and 6.

These are also emphasized in Paris MoU port state inspections, where safety culture and watchkeeping procedures are evaluated.

Best Practices for Staying Sharp

• Bridge Team Management (BTM): Practice simulated collision-avoidance exercises with varied traffic and visibility conditions.
• Use real-world examples: Study accidents from MAIB or NTSB databases.
• Review IMO Model Courses 1.07 and 1.08 on watchkeeping and bridge resource management.
• Daily deck log drills: Use short team discussions or quizzes on COLREG scenarios during watch turnovers.

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Future Outlook: Updating COLREGs for a New Maritime Era

The IMO has begun discussions on how COLREGs might evolve to reflect:

• Unmanned autonomous vessels (MASS)
• Integrated AI-based decision support systems
• Digital twins of vessels aiding risk assessment in real-time

Maritime organizations like The Nautical Institute, IMAREST, and DNV have contributed research papers on how COLREGs can become machine-readable for AI-controlled bridge systems.

Yet, as of 2025, traditional seamanship and human judgment remain the core of collision avoidance.

Frequently Asked Questions (FAQ)

What does COLREGs stand for? The International Regulations for Preventing Collisions at Sea.

Do COLREGs apply in ports or only at sea? They apply in all waters connected to the sea navigable by seagoing vessels, including rivers and ports.

How often should a mariner refresh their COLREG knowledge? IMO recommends regular review through drills and simulator training. Most shipping companies mandate quarterly or annual refresher sessions.

Are there exceptions to the rules? Yes. Rule 2 allows departures from rules in emergencies, and Rule 38 allows exemptions for warships and some government vessels.

Can AI follow COLREGs? To an extent. AI can recognize and act on patterns, but full compliance—especially in complex or ethical decisions—remains a challenge.

Is Rule 5 still valid if you have radar and AIS? Absolutely. Rule 5 emphasizes human lookout, even when using electronic tools.

What’s the most commonly misunderstood rule? Rule 15, involving crossing situations, is frequently misinterpreted under stress or poor visibility.

Conclusion

The COLREGs are not just a checklist—they’re a living framework that saves lives and property at sea. As shipping evolves with AI, smart bridges, and autonomy, the need for clear, confident understanding of navigation rules grows even more urgent.

Mariners must combine traditional skills with modern tools, regularly revisiting COLREGs not just to pass inspections, but to preserve life at sea.

References

• IMO COLREGs Page
• UK MAIB Accident Reports
• STCW Code, IMO Model Courses
• Wärtsilä Smart Marine Ecosystem
• DNV Autonomous Ships R&D
• Paris MoU Inspections
• MarineTraffic Collision Incidents
• The Nautical Institute – COLREGs Refresher
• IMO MASS Regulatory Scoping Exercise