Accident reports often show the same COLREG-related mistakes again and again. They are less about not knowing the rules and more about how the rules are applied in practice.
1. Poor look-out (Rule 5)
Watching only the radar, or one person doing both navigation and look-out. Small craft and fishing gear can be hard to see on radar.
2. Late action
Hesitating until the last minute. Rule 8 asks for action in ample time; an early, large alteration is the safest one.
3. Small, successive alterations
The other vessel may not notice them. Make the alteration large and obvious.
4. Forgetting the stand-on vessel's duty
Rule 17 places obligations on the stand-on vessel too: if the give-way vessel does not act, sound the warning and, when necessary, take your own action.
5. Relying on VHF agreements
Agreeing on the radio to "pass starboard to starboard" does not replace the action the Rules require. You may not be sure which vessel you are talking to.
6. Over-reliance on AIS
AIS data can be incomplete or delayed. Use AIS as an aid, not a replacement for look-out.
7. Speed in restricted visibility
Not reducing speed or preparing the engines when fog sets in.
8. Insufficient radar observation
Deciding on very few observations (Rule 7). A systematic plot and long-range scanning are essential.
How to prevent them
- Speak up on the bridge: say your doubts aloud.
- Call the Master early.
- Do not make decisions when exhausted; respect rest periods.
- Hand over the watch with a clear picture of the traffic.
This article is based on general patterns, not on a particular incident.