Rule text#
Source
(a)When two power-driven vessels are crossing so as to involve risk of collision, the vessel which has the other on her starboard side shall keep out of the way and shall, if the circumstances of the case admit, avoid crossing ahead of the other vessel.
(b)Notwithstanding paragraph (a) of this Rule, on the Great Lakes, Western Rivers, or water specified by the Secretary, a power-driven vessel crossing a river shall keep out of the way of a power-driven vessel ascending or descending the river.
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.
Inland-specific notes#
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.
Authoritative source#
Source links checked against the current public rule corpus on 2026-05-16.
- 33 CFR §83.15 — the section this text comes from, with its neighbours.
- The Inland Navigation Rules are codified at 33 CFR Part 83 and are public domain. The international COLREGs text is published separately by the IMO.
Practice this rule#
One real exam question on this rule, cited to source. No sign-up.
Vessel A is a power-driven vessel proceeding on a steady course. Vessel B, also power-driven, is crossing from Vessel A's port side so as to involve risk of collision. Which statement correctly describes the situation?
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