So you're trying to figure out how Rule 18 fits with Rules 9 and 10, right? Honestly, it trips up a lot of people at sea. The quick answer? Yeah, Rule 18 still applies in narrow channels and traffic separation schemes — but not exactly how you'd think. Rule 9 and 10 kind of muscle in and change things. They're more specific, so they get priority when there's a clash. But Rule 18 isn't totally useless either. Here's the thing with COLREGs — specific beats general every time. Rule 18 sets out who's supposed to give way between different vessel types. Like, sailing boats usually have priority over power-driven ones. But then Rule 9 and 10 come along with their own demands for narrow channels and TSS. When you're in one of those, the specific conduct rules take the wheel. Imagine you're sailing in a TSS lane. Under Rule 18, you'd normally be stand-on against a motor vessel. But Rule 10 says you can't just block a power-driven vessel that's following the lane properly. You're not allowed to impede them. Same deal in narrow channels with Rule 9 — if you're under 20 meters or sailing, you can't get in the way of bigger vessels that need that channel. So your "stand-on" status gets kinda... bent out of shape. Sort of. Rule 18 says RAM vessels usually get right of way over power-driven ones. But Rule 10(i) steps in and says if a RAM vessel is doing safety work in a TSS, they're exempt from some of Rule 10 — only as much as needed for the job. That doesn't mean they can do whatever they want. They still can't just cross a lane if it's gonna cause immediate danger. Their priority isn't a free pass. It's more like a careful balance. Rule 18 basically steps aside when it butts heads with Rule 9 or 10's specific demands. That "impede" thing is the big one. Say you're sailing and a power-driven vessel is in a narrow channel. Rule 18 says you're stand-on. But Rule 9(b) says nope — you can't impede them. So you have to give way, even though Rule 18 normally says otherwise. Same in a TSS under Rule 10(j). Rule 18 isn't dead everywhere though — it still works in situations where there's no impeding issue. When you're stuck trying to figure out which rule wins, run through this: Yeah, under Rule 9(b). If you're sailing and that power-driven boat can only safely use the channel, you can't block them. Rule 18's priority doesn't save you here. No way. Rule 10(i) says fishing vessels can't impede anyone following a lane. They've got to fish outside the lane or get out of the way if something's coming. Yes, fully. Rule 10 only works inside the TSS. Outside of that, you're back to normal rules, including Rule 18. It does, but it's heavily modified. If you're crossing, you've got to do it at right angles and not mess up the traffic flow. Rule 18 only kicks in once you've made sure you're not impeding anyone in the lane.Does rule 18 apply in 9 10 COLREGs
How Do Rules 9, 10, and 18 Interact in a Traffic Separation Scheme?
Does a Vessel Restricted in Her Ability to Maneuver (RAM) Still Have Priority Under Rule 18 in a TSS?
When Does Rule 18 Completely Cease to Apply in Favor of Rules 9 and 10?
Key Differences: When Rule 18 Applies vs. When Rules 9/10 Override
Situation
Rule 18 Applies?
Governing Rule
Example
Power-driven vessel meeting a sailing vessel outside a narrow channel or TSS.
Yes
Rule 18
Sailing vessel is stand-on.
Power-driven vessel meeting a sailing vessel inside a narrow channel.
Partially
Rule 9
Sailing vessel must not impede the power-driven vessel.
Power-driven vessel meeting a fishing vessel in a TSS traffic lane.
Partially
Rule 10
Fishing vessel shall not impede the passage of any vessel following the lane.
Two power-driven vessels meeting head-on in a narrow channel.
No
Rule 9 & 14
Both vessels alter course to starboard. Rule 18 is irrelevant.
Vessel RAM crossing a TSS traffic lane.
Yes (with limits)
Rule 10 & 18
RAM vessel must still avoid crossing if it causes danger, but has special exemptions.
Checklist: Determining the Applicable Rule
Frequently Asked Questions
Does a sailing vessel have to give way to a power-driven vessel in a narrow channel?
Can a fishing vessel block a traffic lane in a TSS?
If a power-driven vessel is outside a TSS, does Rule 18 apply?
Does Rule 18 apply to vessels crossing a TSS traffic lane?
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