Navigation Rules at Sea: The Complete Guide to COLREGs 1972

The oceans serve as the primary arteries of global commerce, facilitating the movement of over eighty percent of international trade. With thousands of cargo ships, tankers, fishing vessels, and recreational craft crisscrossing busy sea lanes daily, the risk of maritime accidents is a constant challenge. To prevent catastrophic accidents, protect human life, and ensure the orderly flow of maritime traffic, the international community relies on a standardized code of navigation standards known as the International Regulations for Preventing Collisions at Sea, widely referred to as COLREGs.

Adopted in 1972 under the auspices of the International Maritime Organization, COLREGs established a comprehensive and legally binding framework for mariners across the globe. Before the modern convention, navigation rules were often a patchwork of local customs, regional treaties, and national statutes. The growth of steamship technology in the nineteenth century and the dramatic increase in vessel speeds and sizes during the twentieth century highlighted the urgent need for a single, universally accepted set of rules. The 1972 Convention replaced the earlier 1960 collision regulations, introducing crucial updates such as recognized Traffic Separation Schemes and modern technical standards for navigation equipment.

What are the colregs rules for collision avoidance?

The primary purpose of COLREGs is to provide unambiguous instructions to vessel operators to prevent dangerous situations at sea. The convention is divided into several sections, with Part A outlining general application and Part B containing the core Steering and Sailing Rules.

Rule 2 sets the tone for the entire convention by establishing the principle of responsibility. Known among mariners as the general prudential rule, it dictates that compliance with the regulations does not relieve any vessel, owner, master, or crew from the consequences of neglect. Mariners must adhere to the ordinary practice of seamen and take all necessary precautions required by special circumstances. This rule grants navigators the legal authority and obligation to depart from technical rules if doing so is strictly necessary to avoid immediate danger.

Rule 6 mandates that every vessel shall at all times proceed at a safe speed. Safe speed is not defined as a fixed knot value; rather, it is a dynamic calculation that depends on prevailing conditions. Mariners must evaluate factors such as the state of visibility, traffic density, vessel maneuverability, draught in relation to available water depth, background lighting at night, and atmospheric conditions such as fog or heavy rain.

Rule 7 focuses on determining whether a risk of collision exists. The rule dictates that every vessel must use all available means, including radar and systematic observation, to assess risk. If there is any doubt as to whether risk exists, navigators are required to assume that it does. One of the primary indicators of collision risk is when the compass bearing of an approaching vessel does not appreciably change as the distance between the vessels decreases.

Rule 8 governs the actions taken to avoid collisions. Any action must be positive, made in ample time, and large enough to be readily apparent to another vessel observing visually or by radar. Small, incremental changes in course or speed must be avoided, as they can cause confusion and obscure intentions.

What is the difference between give way and stand on vessel?

When two vessels approach one another in a manner that involves a risk of collision, COLREGs assigns specific roles to each ship to ensure orderly and predictable maneuvers. These roles are categorized as the give-way vessel and the stand-on vessel under Rules 16 and 17.

The give-way vessel is required by Rule 16 to take early and substantial action to keep well clear of the other vessel. The maneuver must be clear, decisive, and executed far enough in advance so that the other ship's bridge team can confirm the action by visual or electronic means.

Conversely, Rule 17 obligates the stand-on vessel to maintain its course and speed. This requirement ensures predictability, allowing the give-way vessel to execute its avoidance maneuver without guessing what the other ship will do. However, the stand-on vessel's duty is not passive endurance. Rule 17 establishes a three-stage progression of action for the stand-on vessel:

• First, the stand-on vessel must hold its course and speed while monitoring the give-way vessel's actions.
• Second, if it becomes clear that the give-way vessel is not taking appropriate action in compliance with the rules, the stand-on vessel may take action by its own maneuver alone to avoid collision.
• Third, if the distance shrinks to the point where collision cannot be avoided by the give-way vessel alone, the stand-on vessel shall take such action as will best aid to avert collision.

The distinction between give-way and stand-on vessels applies across three primary encounter scenarios in clear visibility:

In an overtaking situation under Rule 13, any vessel coming up on another from a direction more than 22.5 degrees abaft its beam is considered an overtaking vessel and must give way. In a head-on situation under Rule 14, where two power-driven vessels meet on reciprocal courses, neither ship is designated as a stand-on vessel; instead, both vessels must alter their course to starboard so that each passes on the port side of the other. In a crossing situation under Rule 15, the vessel that has the other on its own starboard side must give way and avoid crossing ahead of the other ship.

Visual and Sound Signals: Part C and Part D

To communicate intentions, operational status, and limitations, COLREGs mandates a standardized system of navigation lights, day shapes, and sound signals.

Part C specifies navigation lights that vessels must exhibit from sunset to sunrise, as well as during periods of restricted visibility in daytime. Basic lighting configurations for power-driven vessels underway include a masthead light showing an unbroken white light over an arc of 225 degrees, sidelights displaying green on the starboard side and red on the port side each over an arc of 112.5 degrees, and a sternlight showing a white light over an arc of 135 degrees.

Day shapes, such as spheres, cones, cylinders, and diamonds, are displayed during daylight hours to indicate special vessel operational status. For example, a vessel restricted in her ability to maneuver displays three shapes in a vertical line consisting of a ball, a diamond, and a ball.

Part D regulates sound and light signals. Ships use whistle signals to indicate immediate maneuvers in sight of one another. One short blast signifies a course alteration to starboard, two short blasts signify an alteration to port, and three short blasts indicate operating stern propulsion. Five or more rapid short blasts serve as the danger signal, used when a vessel fails to understand the intentions of another or doubts whether sufficient action is being taken.

How do ships avoid collisions in restricted visibility?

Operating in fog, mist, heavy rainstorms, or falling snow presents severe hazards to marine navigation. Rule 19 specifically addresses the conduct of vessels in conditions of restricted visibility, establishing operational guidelines that differ significantly from clear visibility rules.

Unlike clear visibility scenarios where vessels are split into give-way and stand-on designations based on visual sight, Rule 19 applies to vessels not in sight of one another when navigating in or near areas of restricted visibility. In these situations, every vessel is required to proceed at a safe speed adapted to the prevailing circumstances and conditions. Power-driven vessels must have their engines ready for immediate maneuver.

When detecting another vessel by radar alone, navigators must perform systematic radar plotting to determine whether a close-quarters situation is developing or a risk of collision exists. If a close-quarters situation or collision risk is identified, the navigating officer must take early and substantial avoidance action. Rule 19 provides specific guidelines regarding course alterations based on radar detection alone:

1. Avoid altering course to port for a vessel forward of the beam, except in cases where the ship is overtaking another vessel.
2. Avoid altering course toward a vessel that is abaft or dead abeam.

Furthermore, every vessel that hears the fog signal of another vessel forward of its beam, or cannot avoid a close-quarters situation with another vessel forward of its beam, must reduce speed to the minimum at which the ship can be kept on her course. If necessary, the vessel must take off all her way entirely and navigate with extreme caution until the danger of collision is past.

Sound signals in restricted visibility are governed by Rule 35. A power-driven vessel making way through the water must sound one prolonged blast at intervals of no more than two minutes, while a power-driven vessel underway but stopped and making no way sounds two prolonged blasts separated by a two-second interval every two minutes.

Who is responsible for maintaining a look out at sea?

Rule 5 establishes one of the most fundamental principles in maritime law: every vessel must at all times maintain a proper look-out. The legal obligation to maintain a look-out applies in all weather conditions, in open ocean or congested waterways, and regardless of whether the vessel is underway, at anchor, or drifting.

Responsibility for maintaining a proper look-out rests jointly upon the vessel master, the watchkeeping officers, and dedicated bridge look-out personnel. The rule specifies that a look-out must be maintained by sight and hearing, as well as by all available means appropriate in the prevailing circumstances and conditions. This broad formulation ensures that modern electronic navigation tools are fully integrated into watchkeeping duties.

Effective look-out duties require combining human senses with technological systems:

• Visual observation remains essential for detecting small craft, unlit obstacles, floating debris, and visual light signals that radar or automatic identification systems might miss.
• Auditory monitoring allows bridge personnel to detect whistle signals, fog bells, fog horns, and surf breaking on nearby shoals.
• Radar and Automatic Radar Plotting Aids provide long-range detection, tracking capabilities, and collision risk assessments, particularly during nighttime or thick fog.
• Automatic Identification Systems supply real-time tracking data, vessel names, headings, speeds, and navigation status directly to navigation displays.

The primary purpose of maintaining a proper look-out is to make a full appraisal of the situation and of the risk of collision. Neglecting to maintain a dedicated look-out is repeatedly identified in maritime accident investigations as a primary root cause of ship collisions. A bridge officer distracted by non-essential tasks violates Rule 5 and creates legal liability for any resulting incident.

Future Challenges: Autonomous Ships and Modern Navigation

As technology reshapes the maritime industry, the application of COLREGs faces new questions. The development of Maritime Autonomous Surface Ships, ranging from remotely operated vessels to fully autonomous unmanned ships, presents legal and practical challenges for regulatory bodies.

Current COLREGs rules were drafted under the fundamental assumption that human mariners are physically present on board to observe conditions, make professional judgments, and execute maneuvers. Concepts such as the ordinary practice of seamen and proper look-out by sight and hearing are rooted in human perception and seamanship experience.

To address autonomous technologies, the International Maritime Organization is conducting thorough regulatory scoping exercises. Key areas under examination include how artificial intelligence and machine learning algorithms will interpret situational context under Rule 2, how sensor suites will satisfy Rule 5 look-out obligations, and how communication between automated ships and conventional crewed vessels will occur during crossing or head-on encounters.

Despite technological advancements, the core principles of COLREGs remain the bedrock of collision prevention. Whether navigation decisions are executed by an experienced ship master on the bridge or processed by computer systems, clear rules, predictable behaviors, and strict adherence to safety standards remain indispensable for global maritime safety.

Conclusion

The International Regulations for Preventing Collisions at Sea have served as the vital rulebook for global ocean traffic for nearly half a century. By providing clear guidance on safe speed, collision risk assessment, right-of-way obligations, lighting, sound signals, and watchkeeping duties, COLREGs has significantly reduced maritime casualties and saved countless lives. Understanding and rigorously applying these rules is essential for every navigator, ship owner, and maritime professional committed to preserving safety at sea.