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AI-assisted editorial review · version 3 ·

Rule 34: manoeuvre, doubt and channel intention

A sequence needs context: a manoeuvre in progress is not a proposed passing agreement.

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Manual contents
In this guide
Symbolic patterns, no time scale:34(a) one short starboard, two port, three astern propulsion;34(c) two prolongeds+one short overtake on other’s starboard, two+two on port; agreement prolonged-short-prolonged-short;34(d) at least five rapid shorts. Rule32 durations and scopes written, no audio.
Rule 34 · patterns and context

Original interpretation schematic with declared functions and references. No scale, approved installation or operational track.

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Symbolic patterns, no time scale:34(a) one short starboard, two port, three astern propulsion;34(c) two prolongeds+one short overtake on other’s starboard, two+two on port; agreement prolonged-short-prolonged-short;34(d) at least five rapid shorts. Rule32 durations and scopes written, no audio.

International Rule 34 does not give the same meanings as some US Inland rules. One short blast under 34(a) announces altering course to starboard, not a universal proposal to leave the other on the port side.

Mixing columns in a comparative publication creates a rule that does not exist. The figure shows patterns without audio and with stated contexts.

Short and long rectangles encode duration categories rather than a recording with invented gaps.

Manoeuvring in sight

Rule 34(a) concerns a power-driven vessel underway, in sight of another, manoeuvring as authorised or required. One short means altering to starboard; two, altering to port; three, operating astern propulsion.

The last does not prove astern hull velocity: inertia can retain forward motion. Rule 32 defines short as about one second and prolonged as four to six.

Count, duration and status must be read together.

Paragraph (b) permits supplementing (a)’s whistles with light: one, two or three flashes with the same meanings. Each lasts about one second, gaps between flashes about one second, and gaps between successive signals at least ten seconds.

The light is all-round white, minimum range five miles, conforming to Annex I. It is neither any flashing torch nor a whistle replacement.

Inland yellow and range alternatives are not imported into this international account.

Overtaking intention and agreement

Under 34(c), in sight in a narrow channel or fairway for the 9(e)(i) case, two prolonged and one short indicate intending to overtake on the other vessel’s starboard; two prolonged and two short, on her port. The side belongs to the overtaken vessel.

Her agreement is prolonged-short-prolonged-short in that order. The need for her action to permit safe passing defines the 9(e) context; Rule 13 duty remains.

Agreement does not turn an existing risk into guaranteed clearance.

Doubt and obscuration

Rule 34(d) requires at least five short rapid blasts when approaching vessels in sight fail to understand intentions/actions or doubt the other’s sufficient action. The indication is immediate and can be supplemented by at least five rapid flashes.

It is not exactly five in all circumstances or a general expression of annoyance. Under (e), approaching a bend or area where an obstruction may hide vessels requires a prolonged blast; an approaching vessel within hearing behind the obstruction answers with a prolonged blast.

Paragraph (f) requires one whistle where fitted whistles are separated by over one hundred metres. Rule 33 and Annex III address appliances, not changes in meaning because a boat is small.

Restricted visibility also requires consulting 35; attention and distress have separate references in 36 and 37. The drawing reads International 34 patterns while retaining those conditions.

It emits no signal, gives no appliance setup and approves no manoeuvre.

Sources and references

  1. RIEAM / COLREGs — Rule 9: Narrow channels ↗

    Instituto Hidrográfico / International Maritime Organization · Rule 9, normative Portuguese printed p.11 (PDF p.17); International English cross-check in USCG handbook.

    Rule 9; IH normative Portuguese printed p.11, PDF p.17; English International column cross-check. Individual provision commencement not established: valid_from remains null.

    Checked on
  2. RIEAM / COLREGs — Rule 13: Overtaking ↗

    Instituto Hidrográfico / International Maritime Organization · Rule 13, normative Portuguese printed p.19 (PDF p.25); International English cross-check in USCG handbook.

    Rule 13; IH normative Portuguese printed p.19, PDF p.25; English International column cross-check. Individual provision commencement not established: valid_from remains null.

    Checked on
  3. RIEAM / COLREGs — Rule 36: Signals to attract attention ↗

    Instituto Hidrográfico / International Maritime Organization · Rule 36, normative Portuguese printed p.59 (PDF p.65); International English cross-check in USCG handbook. Rule 37, normative Portuguese printed p.59 (PDF p.65); International English cross-check in USCG handbook.

    Rule 36; IH normative Portuguese printed p.59, PDF p.65; English International column cross-check. Individual provision commencement not established: valid_from remains null. Rule 37; IH normative Portuguese printed p.59, PDF p.65; English International column cross-check. Individual provision commencement not established: valid_from remains null.

    Checked on
  4. USCG amalgamated rules — International current web cross-check ↗

    United States Coast Guard Navigation Center · International/shared Rules 3,20–30,32–35; International Annexes I–III. International-only wording identified by angle-bracket legend; all Inland insertions excluded. Rule35(j)/(k) compared with IH normative Portuguese printed55/PDF61 and English appendix89–90/PDF95–96.

    Directly read 11 October2026 alongside freshly fetched corrected-August2024 official handbook. Current page confirms under12 paragraph(j) and pilot(k); Portuguese IH agrees; its English appendix differs. Access is not qualified legal approval. No unsupported exact consolidation date assigned.

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  5. RIEAM / COLREGs — Rule 35: Sound signals in restricted visibility ↗

    Instituto Hidrográfico / International Maritime Organization · Rule 35, normative Portuguese printed p.55 (PDF p.61); International English cross-check in USCG handbook.

    Rule 35; IH normative Portuguese printed p.55, PDF p.61; English International column cross-check. Individual provision commencement not established: valid_from remains null. Review discrepancy: IH English appendix printed pp.89–90 omits current paragraph (j), the under-12m alternative, and labels pilot clause (j). USCG International Rule35(j)/(k) supplies the current distinction; Editorial source concordance checked 2026-10-11: IH Portuguese normative Rule35(j)/(k), PDF61, and USCG INTERNATIONAL Rule35(j)/(k), PDF113, agree. The IH English appendix omission/misnumbering remains recorded; no professional approval is claimed.

    Checked on
  6. RIEAM / COLREGs — Rule 2: Responsibility ↗

    Instituto Hidrográfico / International Maritime Organization · Rule 3, normative Portuguese printed p.3 (PDF p.9); International English cross-check in USCG handbook.

    Rule 3; IH normative Portuguese printed p.3, PDF p.9; English International column cross-check. Individual provision commencement not established: valid_from remains null.

    Checked on
  7. RIEAM / COLREGs — Rule 32: Definitions of sound signals ↗

    Instituto Hidrográfico / International Maritime Organization · Rule 32, normative Portuguese printed p.53 (PDF p.59); International English cross-check in USCG handbook. Rule 33, normative Portuguese printed p.53 (PDF p.59); International English cross-check in USCG handbook. Rule 34, normative Portuguese printed p.53 (PDF p.59); International English cross-check in USCG handbook.

    Rule 32; IH normative Portuguese printed p.53, PDF p.59; English International column cross-check. Individual provision commencement not established: valid_from remains null. Rule 33; IH normative Portuguese printed p.53, PDF p.59; English International column cross-check. Individual provision commencement not established: valid_from remains null. Rule 34; IH normative Portuguese printed p.53, PDF p.59; English International column cross-check. Individual provision commencement not established: valid_from remains null.

    Checked on
  8. COLREGs Annex I — Positioning and technical details of lights and shapes ↗

    Instituto Hidrográfico / International Maritime Organization · Annex I; printed p.65, PDF p.71; International cross-check USCG.

    Annex I, IH printed p.65 (PDF p.71); cross-check International annex in USCG handbook. Installation/approval is not taught. International/Inland distinction checked in the USCG PDF: International §3(a) half-length/100m agrees with IH; the quarter-length/50m value belongs to U.S. Inland and is not imported. No dimensional installation prescription is reproduced.

    Checked on
  9. COLREGs Annex III — Technical details of sound signal appliances ↗

    Instituto Hidrográfico / International Maritime Organization · Annex III; printed p.77, PDF p.83; International cross-check USCG.

    Annex III, IH printed p.77 (PDF p.83); cross-check International annex in USCG handbook. Installation/approval is not taught.

    Checked on

Regulatory references

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