Fog, underway, International and Inland
Vessel being towed
The manned vessel at the end of a tow.
One prolonged blast, then three short blasts
Who sounds it
A vessel towed, or the last vessel of the tow, if manned.
How it's sounded
Short blast: about 1 second (Rule 32(b)). Prolonged blast: 4 to 6 seconds (Rule 32(c)); 5 seconds is used here. The rule sets no gap between blasts. 1 second is used here so the blasts stay distinct.
At intervals of not more than 2 minutes.
A short blast is about 1 second. A prolonged blast is 4 to 6 seconds. Clips use 1 and 5 seconds.
In or near an area of restricted visibility, by day or by night. You don't have to be inside the fog.
Worth remembering
When practicable, it sounds immediately after the towing vessel's signal, so you hear one long and two short, then one long and three short.
More in fog, underway
- Power vessel making wayInternational and Inlandone prolonged blast
- Power vessel stoppedInternational and Inlandtwo prolonged blasts
- Limited vessels, underwayInternationalone prolonged blast, then two short blasts
- Limited vessels, underwayInlandone prolonged blast, then two short blasts
- Fishing or restricted, at anchorInternationalone prolonged blast, then two short blasts
- Fishing or restricted, at anchorInlandone prolonged blast, then two short blasts
- Composite unit making wayInternational and Inlandone prolonged blast
- Composite unit stoppedInternational and Inlandtwo prolonged blasts
Study more
See every sound signal, try the free Rules of the Road practice test, or read who gives way, and how Inland differs.
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