COLREG - Manoeuvring and Warning Signals (Rule 34)
Sound and light signal pattern for intended manoeuvres or warnings per COLREG Rule 34.
Sound signal
One short blast (~1 sec)
Light signal (optional)
One all-round white flash
Formula, assumptions, and limits
COLREG Rule 34 prescribes sound signals for manoeuvres in sight of one another and for warnings. Signals may be supplemented by all-round white light flashes synchronised with the sound. Short blast = approximately 1 second; prolonged blast = 4 to 6 seconds.
Manoeuvring and warning signals
| Situation | Sound | Light | Rule |
|---|---|---|---|
| Altering to starboard | One short blast | One flash | 34(a)(i) |
| Altering to port | Two short blasts | Two flashes | 34(a)(ii) |
| Operating engines astern | Three short blasts | Three flashes | 34(a)(iii) |
| Narrow channel - overtake on stbd | Two prolonged + one short | n/a | 34(c)(i) |
| Narrow channel - overtake on port | Two prolonged + two short | n/a | 34(c)(i) |
| Narrow channel - agreement | One prolonged, one short, one prolonged, one short | n/a | 34(c)(ii) |
| Doubt - in danger | Five or more short rapid blasts | Five or more flashes | 34(d) |
| Bend or obstruction | One prolonged blast | n/a | 34(e) |
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