COLREGs
COLREGs (Convention on the International Regulations for Preventing Collisions at Sea) are the international rules of the road for vessels at sea. They govern right of way, lights, shapes, and sound signals. Every seafarer is required to know and apply COLREGs to prevent collisions.
Definition
Semantic definition
- Subject
- COLREGs
- Predicate
- are the international rules that
- Object
- govern vessel right of way, lights, shapes, and sound signals to prevent collisions at sea.
COLREGs are the international rules that govern vessel right of way, lights, shapes, and sound signals to prevent collisions at sea.
What are COLREGs?
COLREGs (the Convention on the International Regulations for Preventing Collisions at Sea, 1972) are the universally agreed rules of the road for vessels at sea. Adopted by the IMO and in force since 1977, they apply to all vessels — power-driven, sailing, fishing, or anchored — on the high seas and in waters connected to the high seas. Every seafarer, from a superyacht captain to an RYA Day Skipper, is required by flag state law to know and apply the COLREGs. They define who has right of way (stand-on vessel), who must manoeuvre (give-way vessel), what lights and shapes must be displayed, and what sound signals must be used. Ignorance of COLREGs is not a defence in a collision inquiry.
The Five Parts of COLREGs
COLREGs is structured into five parts plus Annexes. Part A covers application and definitions. Part B covers steering and sailing rules (the rules most mariners need to know and apply). Part C defines lights and shapes. Part D covers sound and light signals. Part E covers exemptions. The Annexes define technical specifications for lights, shapes, and sound signal equipment.
Core Steering and Sailing Rules
Part B — Steering and Sailing Rules — is the most operationally critical section of COLREGs. It covers three situations: vessels in sight of each other (Rules 11-18), vessels in restricted visibility (Rules 19), and conduct in any condition of visibility (Rules 4-10).
Rule 5 — Lookout
Every vessel must maintain a proper lookout at all times, using sight, hearing, and all available means (radar, AIS). A proper lookout is a fundamental duty. Failure to maintain a lookout is a prime factor in nearly every collision investigated by marine accident inquiry bodies (MAIB, NTSB).
Rule 6 — Safe Speed
Every vessel must proceed at safe speed at all times, taking into account visibility, traffic density, vessel manoeuvrability, background lighting, state of sea, and operational condition of radar and other aids. Excessive speed in poor visibility is a persistent cause of collisions.
Rule 8 — Action to Avoid Collision
When action is required to avoid collision, it must be taken in ample time, it must be large enough to be readily apparent to the other vessel, and it must not result in another close-quarters situation. Small, incremental alterations of course or speed are dangerous and non-compliant.
Rule 13 — Overtaking
A vessel overtaking another vessel is the give-way vessel in all circumstances — even if overtaking under sail. The vessel being overtaken is stand-on and must maintain course and speed.
Rule 14 — Head-on Situation
When two power-driven vessels meet head-on (or nearly so), both must alter course to starboard so each vessel passes on the port side of the other. This rule applies whenever there is any doubt about whether the situation is head-on.
Rule 15 — Crossing Situation
When two power-driven vessels cross, the vessel with the other on her starboard side is the give-way vessel. She must keep out of the way and avoid crossing ahead of the stand-on vessel. The stand-on vessel must maintain course and speed.
Rule 16 — Give-way vessel
The give-way vessel must take early and substantial action to keep well clear. "Early" is critical — waiting until the last moment creates collision risk regardless of who is technically give-way.
Rule 17 — Stand-on vessel
The stand-on vessel must initially maintain course and speed but must take action if the give-way vessel fails to act appropriately. The stand-on vessel may act as soon as a collision becomes apparent. Stand-on status does not confer immunity from fault in a collision inquiry.
Rule 18 — Responsibilities between vessels
The hierarchy of give-way responsibility: power-driven vessel gives way to all others under most circumstances; sailing vessels give way to vessels not under command, restricted in ability to manoeuvre, and fishing vessels; vessels constrained by draught have special status in certain situations. Understanding the hierarchy prevents the common assumption that sailing always has right of way.
Navigation Lights Under COLREGs
Part C (Rules 20-31) specifies the lights every vessel must display from sunset to sunrise and during restricted visibility. Correct light configuration is essential both for collision avoidance and for Port State Control compliance. The most important configurations for yacht operators are:
Power-driven vessel underway
Masthead light (white, forward-facing 225°), sidelights (green starboard, red port, each 112.5°), and sternlight (white, aft 135°). Vessels under 50m may use a combined tricolour at the masthead instead of separate masthead + sidelights + stern.
Sailing vessel underway
Sidelights and sternlight only (no masthead steaming light). May use a combined tricolour. Sailing vessels under 7m and vessels under oars may use a combined white all-round light shown in time to prevent collision when normal lights are not practicable.
Vessel at anchor
An all-round white light where best seen (or two all-round white lights fore and aft for vessels over 50m). Vessels over 100m must also illuminate their decks.
Not under command
Two all-round red lights in a vertical line plus sidelights and sternlight when making way.
Shapes and Day Signals
Part C also specifies shapes (black geometric figures) to be displayed by day when a vessel's status must be communicated. Key shapes: a ball indicates a vessel at anchor; two balls in a vertical line indicate a vessel not under command; a diamond indicates a vessel being towed (when tow exceeds 200m); a cone with apex down indicates a vessel under sail and power. Shapes must be at least 0.6m in diameter and must be displayed where they can best be seen.
Sound Signals
Part D (Rules 32-37) specifies sound signals for vessels in sight of each other and in restricted visibility. Key signals: one short blast (one second) — I am altering course to starboard; two short blasts — I am altering course to port; three short blasts — I am going astern; five or more short blasts — danger or doubt signal. In restricted visibility, a power-driven vessel making way sounds one prolonged blast every two minutes; a power-driven vessel underway but stopped sounds two prolonged blasts every two minutes; a vessel at anchor rings a bell rapidly for five seconds every minute.
COLREGs and Traffic Separation Schemes
Rule 10 governs the conduct of vessels in and near Traffic Separation Schemes (TSS). Vessels must use the appropriate traffic lane and proceed in the general direction of traffic flow; vessels crossing a TSS must cross as nearly as practicable at right angles. Yachts under 20m and sailing vessels must not impede the passage of power-driven vessels following a traffic lane. Many major shipping lanes and port approaches are governed by a TSS.
STCW Training and COLREGs Competency
STCW certification (Standards of Training, Certification and Watchkeeping for Seafarers) requires demonstrated competency in COLREGs application as a core assessment element for all watchkeeping officers. The RYA Yachtmaster Offshore and Ocean syllabi include COLREGs as a mandatory element. For commercial yachts, every officer of the watch must be able to demonstrate COLREGs knowledge to port state control standards — not just recite the rules, but apply them to real collision scenarios.
COLREGs for Charter Yachts: Watchkeeping Standards and Officer Responsibility
Commercial charter yachts must maintain a STCW-certified officer of the watch on the bridge or helm station at all times while underway. This is not a recommendation — it is a legal requirement under the STCW Convention, enforced by flag state and Port State Control. The officer of the watch carries direct personal legal responsibility for COLREGs compliance during their watch. When a collision or near-miss occurs, the officer on watch at the time is the primary subject of the marine accident investigation. Marine accident investigations in the United Kingdom are conducted by the Marine Accident Investigation Branch (MAIB); in the United States by the National Transportation Safety Board (NTSB) and the Coast Guard; in France by the BEA-mer; and in other flag states by their equivalent authority. These agencies have independent investigative powers and their findings are published. An investigation that concludes that the officer of the watch failed to maintain a proper lookout (Rule 5) or failed to take action in ample time (Rule 8) can result in the cancellation or suspension of that officer's STCW certificate — the loss of their professional licence. Charter yacht captains carry a responsibility that extends beyond their own watch. They must ensure that every officer on the watchkeeping roster can demonstrate COLREGs competency to the required standard — not merely that they hold the required certificate. STCW certificate holders who have not applied COLREGs in commercial watchkeeping situations may be technically compliant but practically unprepared. Captains should conduct COLREGs scenario assessments as part of crew familiarisation, particularly when an officer joins from a different type of vessel. STCW rest hours requirements directly affect COLREGs compliance planning. Under STCW, watchkeeping officers are entitled to a minimum of 10 hours rest in any 24-hour period and 77 hours in any seven-day period. A watch roster that does not account for these minimums will eventually put a fatigued officer on watch — and fatigue is a primary factor in watchkeeping failures. The captain must demonstrate to Port State Control that the watch schedule complies with STCW rest hours and that COLREGs-qualified personnel are available for every watch. For MCA LY3 vessels (under 24m in commercial operation), the minimum COLREGs competency requirements for crew are specified in the MCA code and in the RYA commercial endorsement requirements. A vessel operating commercially in Category 0 or Category 1 waters (offshore) must have a qualified watchkeeper whose certification matches the operational area. Even in Category 6 (sheltered waters) commercial operation, the watch officer is still bound by COLREGs and personally responsible for collision avoidance.
COLREGs for Yachts Under 24m: Common Mistakes and Practical Application
Smaller yachts — particularly those under 24m or under 20m — have simplified light configuration options under COLREGs, but they are fully subject to all collision avoidance rules. The simplified light provisions (combined tricolour at masthead, all-round white for vessels under 7m) do not create any relaxation of the steering and sailing rules. A yacht under 12m that fails to display correct anchor lights in an anchorage frequented by commercial vessels is in breach of COLREGs and is creating a collision risk for which it will bear fault. Common mistakes on smaller yachts include: assuming a sailing yacht always has right of way (it does not when overtaking, when operating in a TSS, or when approaching a vessel constrained by draught or not under command); anchoring in traffic lanes or approaches without proper anchor lights; failing to display the correct shape for motor-sailing (an inverted cone — meaning the yacht is technically a power-driven vessel for COLREGs purposes); and maintaining inadequate lookout when one crew member is sleeping and the other is helming without a dedicated watch. The TSS interaction problem is particularly common for yachts crossing major shipping lanes. Rule 10 is explicit: vessels under 20m and sailing vessels must not impede the safe passage of a power-driven vessel following a traffic lane. This does not mean smaller yachts are prohibited from crossing TSS lanes — they may cross, but they must do so at right angles to the traffic flow and must not require large commercial vessels to manoeuvre around them. A yacht that enters a TSS lane and proceeds along it in the same direction as shipping traffic, at a fraction of the speed, is creating a hazardous situation that Rule 10 prohibits. Radar watch requirements for yachts in busy commercial shipping areas are implicit in Rule 5 (proper lookout by all available means) and Rule 7 (risk of collision assessment). A yacht without radar or AIS in a major shipping lane at night is relying only on visual lookout for vessels that may be travelling at 20+ knots — the visual acquisition time at those closing speeds in darkness is dangerously short. At minimum, AIS reception and a functioning VHF radio are the operational baseline for any yacht transiting areas with commercial traffic density. Rule 19 — restricted visibility — is frequently misunderstood on smaller yachts. The rule requires proceeding at a safe speed that takes into account all circumstances, including visibility. It does not permit continuing at full speed in fog on the basis that radar is fitted. It requires engines to be on standby (manoeuvring mode), a proper sound signal watch, and radar plotting of all detected contacts. Many smaller yacht engines are not manoeuvrable enough at slow speeds to satisfy the intent of Rule 19 in dense commercial traffic. Slowing down, calling the shipping lane via VHF on Channel 16, and waiting for visibility to improve is often the correct action.
COLREGs Violations and Collision Inquiries
When a collision or near-miss (close-quarters situation) occurs involving a commercial yacht, the sequence of events that follows is defined by maritime law. The master has a legal duty under SOLAS Regulation V/33 to render assistance to any vessel in distress and to report the incident to the flag state authority and the coastal state authority of the nearest port. Failure to render assistance is a criminal offence in most jurisdictions, separate from any COLREGs fault finding. The flag state or coastal state authority conducts a formal investigation. In practice, for incidents occurring in European waters, the MAIB (UK), BEA-mer (France), BSU (Germany), or equivalent national authority investigates even if the vessel is foreign-flagged, if the incident occurred in their territorial waters or affected their coast. These investigations have statutory powers to compel the production of the vessel log, AIS records, radar plots, chart plotter tracks, VHF radio logs, and witness statements from all crew. COLREGs violations established in an investigation lead to three concurrent consequences. First, the flag state may take certificate action against the master and/or the officer of the watch — suspension or cancellation of their STCW certificates, removing their ability to sail professionally. Second, civil liability proceedings follow in the relevant jurisdiction, with fault apportioned between the vessels involved. Unlike road traffic law, both vessels can be found at fault — an 80/20 or 50/50 apportionment is common where both vessels contributed to the situation. Third, the vessel owner's insurance is affected: a finding of COLREGs fault increases premiums and may affect claim recovery. Post-incident evidence management is a critical and often neglected operational matter. The chart plotter track log, AIS data from a connected receiver, radar echo log (if radar has track recording capability), and VHF Channel 16 recordings are all potential evidence. On modern ECDIS and chart plotter systems, these records can be overwritten if the equipment is not isolated quickly after an incident. Best practice is to immediately disable track log overwriting, capture screenshots of the track and AIS targets in the minutes before and during the incident, and note the time synchronisation status of all instruments. Preservation of this data materially affects the ability to reconstruct what happened and to establish or defend against fault findings. Insurance P&I clubs (Protection & Indemnity clubs, which insure third-party liability for most superyachts and commercial yachts) handle the legal aftermath of collisions. The P&I club's correspondent in the port of incident should be contacted immediately. They will advise on local legal representation, survey of both vessels for damage assessment, and the procedural steps required under the applicable maritime law. Cooperation with the P&I club from the first moment is essential to preserving the vessel owner's legal position.
Frequently Asked Questions
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