COLREGs · Rule 34
Maneuvering and Warning Signals
Last verified: 2026-06-02
TL;DR
International: 1 short = 'I am altering course to starboard'; 2 short = port; 3 short = engines astern. Overtaking in a narrow channel: 2 long + 1 short (overtake on stbd) / 2 long + 2 short (port). Doubt: 5+ short.
Why it shows up on the exam
Inland Rule 34 has a critical difference: under Inland, sound signals are signals of INTENT not action — answered by the other vessel agreeing or sounding the doubt signal.
Exam checkpoints
COLREGs action
1 / 2 / 3 short blasts
In International waters, one short blast means altering course to starboard, two short blasts means altering course to port, and three short blasts means operating astern propulsion.
Inland intent
Leave you port / starboard
Inland Rule 34 uses the same one- and two-short-blast patterns as meeting, crossing, or overtaking signals of intent: one short means intending to leave the other vessel on your port side, and two short means intending to leave her on your starboard side.
Warning signal
5 or more short blasts
Five or more short and rapid blasts is the danger or doubt signal. It belongs on both COLREGs and Inland exams and is the answer when another vessel's intentions are unclear.
Authoritative source
Source links checked against the current public rule corpus on 2026-06-02.
- 33 CFR §83.34— verbatim Inland Rule text (US Code of Federal Regulations)(retrieved 2026-06-02)
- International COLREGs Rule 34 verbatim text is published by the IMO. The Inland counterpart 33 CFR §83 chunk above mirrors the international wording almost verbatim.
Rule questions
What does Rule 34 cover?
Rule 34 covers maneuvering and warning signals. It gives the short-blast codes for course changes, astern propulsion, overtaking in narrow channels, bend or obstruction warnings, and the five-or-more-short-blast danger signal.
What do one, two, and three short blasts mean under COLREGs?
Under COLREGs Rule 34, one short blast means 'I am altering my course to starboard,' two short blasts means 'I am altering my course to port,' and three short blasts means 'I am operating astern propulsion.'
Why is Inland Rule 34 different from COLREGs Rule 34?
Inland Rule 34 treats one- and two-short-blast meeting, crossing, and overtaking signals as intent signals. One short means 'I intend to leave you on my port side'; two short means 'I intend to leave you on my starboard side.' The other vessel must answer with agreement or use the danger signal.
What does five short blasts mean?
Five or more short and rapid blasts means danger or doubt. Use it when you do not understand another vessel's intentions or doubt whether enough action is being taken to avoid collision.
Inland parallel
Inland Rule 34 — Maneuvering and Warning Signals →More from Part D — Sound and Light Signals
Related drills
- Practise Rule 32 — Sound Signal Definitions
- Rule 33 — Equipment for Sound Signals
- Practise Rule 35 — Sound Signals in Restricted Visibility
- Rule 36 — Signals to Attract Attention
Drill COLREGs Rule 34
Try the free Rules of the Road practice questions (no sign-in), or sign in to drill citation-backed questions on this rule with immediate feedback and the source chunk in a popover.