Part D — Sound and light signals
COLREGs Rule 35: Sound signals in restricted visibility
Rule 35 sets the fog signals, sounded at least every two minutes: one prolonged blast for a power-driven vessel making way, two for one stopped, and one prolonged followed by two short for sailing, fishing, towing, NUC, RAM and CBD vessels.
What Rule 35 says
- Power-driven, making way: one prolonged blast at intervals of not more than 2 minutes.
- Power-driven, underway but stopped: two prolonged blasts about 2 seconds apart, at least every 2 minutes.
- Not under command, restricted, constrained by draught, sailing, fishing or towing/pushing: one prolonged followed by two short blasts, at least every 2 minutes. Fishing and RAM vessels at anchor use this signal too.
- A manned vessel towed, or the last of a tow: one prolonged followed by three short blasts, straight after the towing vessel's signal.
- At anchor: rapid ringing of the bell for about 5 seconds at least every minute (over 100 m, followed by a gong aft). May add short, prolonged, short to warn an approaching vessel.
- Aground: the bell signal with three separate, distinct strokes before and after it.
- Vessels 12–20 m need not give the bell signals; vessels under 12 m need not give any of these, but both must make some other efficient sound signal at least every 2 minutes.
- A pilot vessel on duty may also sound four short blasts.
This is a plain-English summary, not the official wording. For the exact text, see the IMO convention. In UK waters the rules are given legal force by the Merchant Shipping (Distress Signals and Prevention of Collisions) Regulations.
What it means on a yacht
A sailing yacht in fog sounds one long and two short every two minutes; motoring, it sounds one long. Set a timer so the signal does not get forgotten during a tense passage.
| Signal | Meaning | When |
|---|---|---|
| Prolonged | Power-driven vessel making way | Every 2 minutes |
| Prolonged, prolonged | Power-driven vessel underway but stopped | Every 2 minutes |
| Prolonged, short, short | Sailing, fishing, towing, NUC, RAM or CBD vessel | Every 2 minutes |
| Prolonged, short, short, short | Last vessel of a manned tow | Every 2 minutes |
| Bell | At anchor — rapid ringing of the bell for 5 seconds | Every minute |
| Short, prolonged, short | At anchor — optional warning to an approaching vessel | As needed |
| Short, short, short, short | Pilot vessel on duty (in addition to her other signals) | Optional |
Practise it
Test yourself on who gives way in the free COLREGs trainer, or print the rules of the road cheat sheets for the chart table.
Other rules in Part D
- Rule 32: Definitions of sound signals
- Rule 33: Equipment for sound signals
- Rule 34: Manoeuvring and warning signals
- Rule 36: Signals to attract attention
- Rule 37: Distress signals