COLREGs · Rule 15 · 33 CFR §83.15
Crossing Situation
When two power-driven vessels are crossing so as to involve risk of collision, the vessel which has the other on her own starboard side shall keep out of the way and shall, if circumstances admit, avoid crossing ahead of the other.
What does Rule 15 actually say?#
Source
Practice this rule#
One real exam question on this rule, cited to source. No sign-up.
Under the Inland Rules, two power-driven vessels are crossing a river. Vessel A is ascending the river; Vessel B is crossing the river. Which vessel keeps out of the way?
How does Inland Rule 15 differ from COLREGs?#
Inland Rule 15(b) gives a power-driven vessel crossing a Western River or the Great Lakes the right-of-way if the other is descending the river.
21 of 38 rules differ somewhere; the five the exam leans on are Rule 9, Rule 10, Rule 24, Rule 28 and Rule 34, side by side on Inland vs International Rules.
Why it shows up on the exam#
Mnemonic: 'green over green, no problem seen' is wrong — green-on-your-starboard means you are the give-way vessel.
What does the exam actually test here?#
Who gives way
The one with the other to starboard
When two power-driven vessels are crossing so as to involve risk of collision, the vessel which has the other on her own starboard side keeps out of the way.
How
Avoid crossing ahead
The give-way vessel shall, if the circumstances of the case admit, avoid crossing ahead of the other vessel. Combined with Rule 8, that normally means a substantial early alteration to starboard to pass astern.
The Inland exception
Crossing a river
On the Great Lakes, Western Rivers, or waters specified by the Secretary, a power-driven vessel crossing a river keeps out of the way of a power-driven vessel ascending or descending the river — regardless of which side she is on.
Rule 15 — common exam questions#
In a crossing situation, who is the give-way vessel?
The vessel which has the other on her own starboard side keeps out of the way (33 CFR §83.15(a)). The other vessel is the stand-on vessel and is governed by Rule 17.
What does 'avoid crossing ahead' mean in practice?
Rule 15(a) directs the give-way vessel, if circumstances admit, not to pass in front of the stand-on vessel. Read with Rule 8, the expected answer is an early, substantial alteration to starboard that takes you astern of her.
What is the Inland river-crossing rule?
On the Great Lakes, Western Rivers, or waters specified by the Secretary, a power-driven vessel crossing a river must keep out of the way of a power-driven vessel ascending or descending the river (33 CFR §83.15(b)). COLREGs has no equivalent.
Does Rule 15 apply between a sailing vessel and a power-driven vessel?
No. Rule 15 governs two power-driven vessels crossing. Sail against power is a Rule 18 question.
Authoritative source#
- 33 CFR §83.15 — this section with its neighbours. 33 CFR Part 83 is public domain; checked 2026-05-16.
- COLREGs Rule 15 is published by the IMO and is authoritative internationally.
Practise this rule against the real exam.
Real exam questions. No signup, no card.
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