{"id":51605,"date":"2026-04-17T21:26:19","date_gmt":"2026-04-17T20:26:19","guid":{"rendered":"https:\/\/maritimehub.co.uk\/?p=51605"},"modified":"2026-04-17T21:26:19","modified_gmt":"2026-04-17T20:26:19","slug":"colregs-narrow-channels-tss-overtaking","status":"publish","type":"post","link":"https:\/\/maritimehub.co.uk\/colregs-narrow-channels-tss-overtaking\/","title":{"rendered":"COLREGs \u2013 Narrow Channels, TSS & Overtaking"},"content":{"rendered":"
\n

BRIDGE \u2192 Rules of the Road<\/strong><\/p>\n

Position on the Bridge<\/strong><\/p>\n

System Group:<\/strong> Navigation \/ Collision Avoidance<\/p>\n

Primary Role:<\/strong> Defines the precise obligations governing vessel conduct in constrained and regulated waters, and during overtaking situations<\/p>\n

Interfaces:<\/strong> ECDIS, AIS, VHF, VTS, pilot communications, OOW watchkeeping judgement<\/p>\n

Operational Criticality:<\/strong> Absolute \u2013 errors in interpretation or application directly produce collision and grounding risk<\/p>\n

Failure Consequence:<\/strong> Misapplication of Rule 9, 10 or 13 in confined or regulated waters leads to close-quarters situations, collision, enforcement action, detention, and criminal liability for the master<\/p>\n<\/div>\n

The Rules do not exist to be recited at examination.<\/em>
They exist to be applied at 0300, in rain, with a following sea and a VTS frequency that will not clear.<\/em><\/p>\n

Introduction<\/h2>\n

Rules 9, 10 and 13 of the International Regulations for Preventing Collisions at Sea sit at the intersection of geography, traffic management, and the most fundamental question in collision avoidance: who is obliged to do what, and when. They are also the rules most frequently cited in post-incident investigations and enforcement proceedings. Not because they are obscure, but because they are misread by officers who believe they understand them.<\/p>\n

The misreading follows a pattern. A watchkeeper learns the headline obligation, applies it mechanically, and misses the conditional structure underneath. Rule 9 becomes “keep to starboard.” Rule 10 becomes “stay in your lane.” Rule 13 becomes “the overtaking vessel gives way.” Each of those summaries is broadly true. Each of them, applied without the surrounding context, has contributed to collisions.<\/p>\n

This article treats the three rules as they operate in practice: interacting with each other, with VTS requirements, with the geography of the water, and with the professional judgement of an officer who cannot pause to consult a textbook.<\/p>\n

The purpose is not to reproduce the text of the Rules. Any officer can read the text. The purpose is to examine what the text actually requires, where interpretation is genuinely contested, and where common practice falls short of legal obligation.<\/p>\n

Contents<\/h2>\n
    \n
  • 1. Rule 9 \u2013 The Narrow Channel in Full<\/li>\n
  • 2. The Safe Water Obligation and the “As Far as Practicable” Trap<\/li>\n
  • 3. Small Vessel and Fishing Vessel Obligations Under Rule 9<\/li>\n
  • 4. Rule 10 \u2013 Traffic Separation Schemes: Structure and Status<\/li>\n
  • 5. Crossing, Joining, and the Inshore Traffic Zone<\/li>\n
  • 6. What “Following the General Direction of Traffic Flow” Actually Means<\/li>\n
  • 7. Rule 13 \u2013 Overtaking: Status, Duration, and the Moment of Completion<\/li>\n
  • 8. Common Violations and Enforcement Patterns<\/li>\n
  • Closing Reality<\/li>\n<\/ul>\n

    1. Rule 9 \u2013 The Narrow Channel in Full<\/h2>\n

    Rule 9 applies when a vessel is in a narrow channel or fairway. The Rule does not define “narrow channel” by width, depth, or charted designation. It defines it by navigational constraint: a channel is narrow when a vessel of the relevant draught is effectively confined to it for safe navigation. A deep-draught tanker in a buoyed approach channel may be operating in a narrow channel. A coastal cruiser in the same channel may not be, because it has water to spare on either side. The same geographical space can attract different Rule 9 obligations depending on the vessel.<\/p>\n

    That distinction matters. It determines whether a vessel must keep to the starboard side, whether it must not impede, and whether it enjoys the priority of a vessel that cannot safely navigate outside the channel.<\/p>\n

    The primary obligation is to keep to the starboard outer limit of the channel or fairway as far as safe and practicable. Not to the centreline. Not to the buoyed fairway in general terms. To the starboard side. Vessels consistently navigating the centreline in narrow channels are not in compliance, regardless of how standard that practice may feel on a quiet watch.<\/p>\n

    2. The Safe Water Obligation and the “As Far as Practicable” Trap<\/h2>\n

    The phrase “as far as safe and practicable” is the operating margin Rule 9 provides. It exists because the starboard edge of a channel may contain shoals, wrecks, overfalls, or cross-traffic from marinas. The Rule acknowledges navigational reality.<\/p>\n

    What it does not do is authorise comfortable centreline navigation because the starboard side looks inconvenient.<\/p>\n

    In enforcement proceedings, “as far as practicable” has repeatedly been examined. Courts and flag state investigators have held consistently that it requires an active assessment of what is actually preventing movement toward the starboard limit, not a general preference for sea room. An officer who cannot articulate what specific hazard prevented starboard-side navigation has not met the standard.<\/p>\n

    The watch log and the ECDIS track tell that story with precision. They are used against vessels in collision investigations with regularity.<\/p>\n

    Rule 9(b) prohibits anchoring in a narrow channel except in cases of necessity. This is an absolute prohibition, not a guidance note. Anchoring in a buoyed fairway because the berth is not ready is a Rule 9 violation. Port operational convenience does not override the Collision Regulations.<\/p>\n

    3. Small Vessel and Fishing Vessel Obligations Under Rule 9<\/h2>\n

    Rule 9(b) contains an obligation directed at vessels under 20 metres and sailing vessels: they shall not impede the passage of a vessel that can only safely navigate within the channel. Rule 9(c) places the same obligation on fishing vessels.<\/p>\n

    This is not a give-way rule. It is an impeding rule. The distinction is critical.<\/p>\n

    A give-way obligation activates when a collision risk exists. The obligation not to impede activates earlier, before risk has developed, and requires positive action to stay clear of a vessel that is constrained to the channel. A sailing vessel that forces a laden tanker to take avoiding action in a narrow channel has violated Rule 9 even if no close-quarters situation developed. The MCA has issued enforcement guidance on this point, and harbour authorities have prosecuted accordingly.<\/p>\n

    For the large vessel master, the corollary is this: the existence of Rule 9(b) and 9(c) obligations on smaller vessels does not remove the large vessel’s obligation to navigate prudently. Rule 9 does not create a right of way in the conventional sense. It creates a structured set of obligations. Both vessels can be in violation simultaneously.<\/p>\n

    4. Rule 10 \u2013 Traffic Separation Schemes: Structure and Status<\/h2>\n

    Traffic Separation Schemes adopted by the IMO have a specific legal status. Rule 10 governs conduct within them, but Rule 10(a) makes clear it does not relieve any vessel of its other obligations under the Rules. TSS navigation is not a substitute for collision avoidance. It is a layer of ordered traffic management on top of it.<\/p>\n

    The scheme structure matters. A TSS consists of traffic lanes, a separation zone between opposing lanes, and potentially inshore traffic zones between the separation zone and the coast. A vessel in a traffic lane is required to proceed in the general direction of traffic flow for that lane. A vessel in the separation zone is required to avoid anchoring there except in an emergency. These are specific requirements, not aspirational guidance.<\/p>\n

    Rule 10 applies to all vessels underway in a TSS. It does not apply only to vessels above a certain size, and it does not exclude vessels that are merely transiting the area rather than “using” the scheme as a regular route. If the vessel is in a TSS, Rule 10 obligations attach.<\/p>\n

    Fishing within a TSS is not prohibited by Rule 10, but fishing vessels shall not impede the passage of vessels following a traffic lane. In practice, fishing vessels working across or near traffic lanes in adopted TSS areas are a recurrent source of near-miss reports. The obligation is on the fishing vessel, but the prudent watch officer does not rely on that to manage the risk.<\/p>\n

    5. Crossing, Joining, and the Inshore Traffic Zone<\/h2>\n

    Rule 10(c) requires that a vessel crossing a traffic lane do so on a heading as nearly as practicable at right angles to the general direction of traffic flow. This is the most consistently violated provision in Rule 10, and the one that causes the most confusion about intent.<\/p>\n

    The requirement is for a heading at right angles, not a track made good at right angles. In a tidal stream, these are different things. A vessel that compensates for tide to achieve a right-angle track across the lane is not in compliance with Rule 10(c) unless that track is achieved by a heading that is itself at right angles. The purpose is visibility of intent: a vessel approaching a traffic lane at 90 degrees signals a clear crossing intention to ships in the lane. A vessel approaching at an oblique angle, however tidy its track, creates ambiguity.<\/p>\n

    In strong tidal conditions this creates genuine difficulty. The Rule accepts the limitation. What it does not accept is an approach angle that is oblique because it is operationally convenient.<\/p>\n

    The inshore traffic zone is available to vessels of less than 20 metres, sailing vessels, and vessels engaged in fishing. It is also available to any vessel that is proceeding to or from a port, pilot station, or offshore installation situated within the inshore traffic zone. This is a defined list. A vessel that does not fall within it should not be in the inshore zone without good reason, and “avoiding the traffic lane” is not, by itself, a good reason that satisfies Rule 10.<\/p>\n

    Large vessels taking a shortcut through the inshore zone to avoid traffic-lane congestion are in violation. This has been the subject of enforcement action in the Dover Strait, the Channel Islands approaches, and the Traffic Separation Scheme off Ushant.<\/p>\n

    6. What “Following the General Direction of Traffic Flow” Actually Means<\/h2>\n

    Rule 10(b)(i) requires a vessel using a traffic lane to proceed in the general direction of traffic flow. General direction is the operative phrase. It does not require a vessel to be perfectly parallel to the lane boundaries at all times. It requires the vessel to be broadly aligned with the intended flow of traffic through that lane.<\/p>\n

    A vessel proceeding at an acute angle to the lane direction while technically within the lane boundaries is not following the general direction of traffic flow. This situation arises when vessels make large course alterations within a lane to avoid traffic ahead, when vessels enter a lane from an oblique angle without correcting onto the lane direction, or when a vessel is cutting across one lane to reach the next, using the separation zone as a turning area.<\/p>\n

    The separation zone is not a manoeuvring area. Rule 10(d) prohibits crossing it unless it is necessary to avoid immediate danger, or to cross from one traffic lane to the other. Vessels are not to navigate within the separation zone when there is no operational necessity to do so.<\/p>\n

    A quiet bridge watch does not indicate that the vessel’s conduct in a TSS is compliant.<\/p>\n

    VTS authorities in major TSS areas \u2014 Strait of Dover CNIS, Ushant Traffic, the Singapore Strait \u2014 actively monitor vessel tracks and heading relative to lane boundaries. Deviations are logged. Persistent non-compliance generates formal reports. Masters have been summoned to explain track records extracted from VTS radar recordings after incidents that might otherwise have been treated as minor.<\/p>\n

    7. Rule 13 \u2013 Overtaking: Status, Duration, and the Moment of Completion<\/h2>\n

    Rule 13 defines an overtaking vessel as one approaching another from more than 22.5 degrees abaft the beam. Once that condition is met, the approaching vessel is overtaking and is the give-way vessel. This is straightforward.<\/p>\n

    What is less well understood is the duration of that status.<\/p>\n

    Rule 13(d) is explicit: any doubt about whether a vessel is overtaking shall be resolved by treating the vessel as overtaking. And the give-way obligation persists until the overtaking vessel is finally past and clear. Not when it has drawn abeam. Not when it has moved past the midships of the overtaken vessel. Finally past and clear: a condition that requires the overtaking vessel to have moved sufficiently ahead that the risk of collision from that manoeuvre has completely resolved.<\/p>\n

    In a narrow channel, this has specific implications. An overtaking vessel that has driven past the overtaken vessel but then slows for a berth, a lock, or a fairway bend has not completed the overtaking manoeuvre. If the overtaken vessel is then forced to take action because the overtaking vessel is no longer maintaining the separation of the manoeuvre, the overtaking vessel remains the give-way vessel and remains in violation.<\/p>\n

    Rule 9(e) adds a further layer specifically for narrow channels. In a narrow channel, a vessel shall not overtake unless the overtaken vessel has signalled its agreement, using the relevant sound signal sequence. This is not a courtesy requirement. It is a mandatory signalling exchange before any overtaking manoeuvre begins in a narrow channel.<\/p>\n

    In practice, this exchange rarely happens. VHF contact is substituted. Port authority instructions are treated as consent. Neither is compliant with the Rule. A VHF agreement to overtake in a narrow channel may be good seamanship and may reflect sensible operational practice, but it is not the mechanism Rule 9(e) requires.<\/p>\n

    The five-short-blast signal given by a vessel that does not agree to the overtaking manoeuvre is an absolute prohibition on proceeding. A vessel that ignores five short blasts and overtakes anyway is not merely in procedural violation. It is navigating in direct contravention of the expressed intent of the overtaken vessel, and assumes full responsibility for any subsequent incident.<\/p>\n

    8. Common Violations and Enforcement Patterns<\/h2>\n

    Enforcement action under Rules 9, 10 and 13 follows recognisable patterns. Understanding those patterns is useful, not because it helps a vessel avoid detection, but because it identifies where real collision risk concentrates.<\/p>\n

    The most common Rule 9 violations recorded in MCA and MAIB files involve centreline navigation in approach channels, anchoring in fairways on commercial instructions from agents, and large vessels failing to act on the impeding obligations of small craft until a close-quarters situation has already developed. The third category regularly involves passages where the large vessel’s bridge team saw the small vessel early, expected it to comply with Rule 9(b), and took no action until forced to.<\/p>\n

    Expectation of compliance by other vessels is not a collision avoidance strategy.<\/p>\n

    Rule 10 violations most frequently recorded by VTS authorities involve crossing angles significantly less than 90 degrees, vessels using the inshore traffic zone without meeting the stated criteria, vessels altering course within separation zones for traffic-avoidance purposes, and vessels failing to correct onto the lane direction after joining from an oblique approach. AIS data and VTS radar recordings provide the evidence base. These violations are increasingly prosecuted rather than simply noted.<\/p>\n

    Rule 13 violations concentrate around two failure modes. The first is premature termination of give-way status: the overtaking vessel considers itself past and clear before it genuinely is, and begins manoeuvring for the next objective. The second is the failure to use the Rule 9(e) sound signal exchange before overtaking in a narrow channel, followed by an overtaking manoeuvre that the overtaken vessel was not anticipating. Both failure modes have featured in fatal collision investigations.<\/p>\n

    It is worth noting that Rules 9, 10 and 13 do not exist in isolation. Rule 16 requires a give-way vessel to take early and substantial action. An overtaking vessel that makes a series of small, late alterations while relying on the stand-on vessel to hold course is not fulfilling its Rule 13 obligation even if its final action prevents collision. The standard is early, substantial, and unambiguous.<\/p>\n

    In TSS areas, Rule 13 applies alongside Rule 10. A vessel overtaking within a traffic lane must give way under Rule 13 while maintaining compliance with Rule 10(b). These obligations run in parallel and neither suspends the other.<\/p>\n

    Closing Reality<\/h2>\n

    Rules 9, 10 and 13 are not complicated rules. They are precise rules, and precision requires more than memory of the headline obligation.<\/p>\n

    The narrow channel demands starboard-side navigation and a mandatory exchange before any overtaking begins. The TSS demands right-angle crossings, legitimate use of the inshore zone, and genuine alignment with the traffic flow. Overtaking status persists until the manoeuvre is complete \u2014 not until the overtaking vessel loses interest in it.<\/p>\n

    None of this is difficult to apply when understood. It becomes difficult only when officers apply condensed summaries under pressure and trust that general compliance is good enough.<\/p>\n

    General compliance is not the standard. The Rules specify what is required. VTS systems record what actually happens. The gap between those two things is where collisions and enforcement actions occur.<\/p>\n

    The ECDIS track does not lie. Neither does the VTS recording. Both will be produced in any inquiry that follows.<\/p>\n","protected":false},"excerpt":{"rendered":"

    Rules 9, 10 and 13 examined in operational depth: the obligations masters and officers must internalise, not just cite.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"fifu_image_url":"","fifu_image_alt":"","c2c-post-author-ip":"2a02:c7c:2ef8:2400:931:afb1:9971:4a62","footnotes":""},"categories":[10,1],"tags":[9076,7796,9138,9140,9136,9137,9135,9139],"class_list":["post-51605","post","type-post","status-publish","format-standard","hentry","category-bridge","category-latest","tag-collision-avoidance","tag-colregs","tag-narrow-channels","tag-overtaking","tag-rule-10","tag-rule-13","tag-rule-9","tag-traffic-separation-scheme"],"acf":[],"_links":{"self":[{"href":"https:\/\/maritimehub.co.uk\/?rest_route=\/wp\/v2\/posts\/51605","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/maritimehub.co.uk\/?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/maritimehub.co.uk\/?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/maritimehub.co.uk\/?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/maritimehub.co.uk\/?rest_route=%2Fwp%2Fv2%2Fcomments&post=51605"}],"version-history":[{"count":1,"href":"https:\/\/maritimehub.co.uk\/?rest_route=\/wp\/v2\/posts\/51605\/revisions"}],"predecessor-version":[{"id":51619,"href":"https:\/\/maritimehub.co.uk\/?rest_route=\/wp\/v2\/posts\/51605\/revisions\/51619"}],"wp:attachment":[{"href":"https:\/\/maritimehub.co.uk\/?rest_route=%2Fwp%2Fv2%2Fmedia&parent=51605"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/maritimehub.co.uk\/?rest_route=%2Fwp%2Fv2%2Fcategories&post=51605"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/maritimehub.co.uk\/?rest_route=%2Fwp%2Fv2%2Ftags&post=51605"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}