Inland vs International Navigation Rules: The Differences That Matter

Here's what makes this topic tricky: the Inland Navigation Rules and the International COLREGS look almost identical. Same rule numbers, same structure, mostly the same words. Then a single paragraph changes the answer. This guide lays out the differences you're most likely to see, with rule numbers, and a method for keeping them straight.

Which rules apply where?

The International rules (the 72 COLREGS) apply on the high seas and connected waters navigable by seagoing vessels. The U.S. Inland Navigation Rules, found in 33 CFR Part 83, apply on U.S. inland waters, including the Great Lakes and Western Rivers. The boundary between the two is set by the COLREGS Demarcation Lines in 33 CFR Part 80. On an exam, the question will usually tell you which waters you're in. Read that first, every time.

Rule 9: Narrow channels

Both versions say a vessel in a narrow channel keeps as near to the outer limit on her starboard side as is safe and practicable.

Inland adds Rule 9(a)(ii): on the Great Lakes, Western Rivers, or waters specified by the Secretary, a power-driven vessel proceeding downbound with a following current has the right-of-way over an upbound vessel. She proposes the manner and place of passage and initiates the maneuvering signals of Rule 34(a)(i). The upbound vessel holds as necessary to permit a safe passing.

The overtaking signals in a narrow channel also differ. International Rule 9(e) points to the Rule 34(c) signals using prolonged and short blasts. Inland uses its own Rule 34(c) signals of one or two short blasts. More on those below.

Rules 14 and 15: Head-on and crossing on rivers

The basic head-on and crossing rules match. Inland adds two twists:

Inland Rule 14(d): on the Great Lakes, Western Rivers, or specified waters, a power-driven vessel downbound with a following current has the right-of-way over an upbound vessel and proposes the manner of passage.
Inland Rule 15(b): on the Great Lakes, Western Rivers, or specified waters, a power-driven vessel crossing a river keeps out of the way of a power-driven vessel ascending or descending the river.

Rules 23 and 24: Lights for power-driven and pushing vessels

Inland Rule 23(e): a power-driven vessel on the Great Lakes may carry an all-round white light in place of the second masthead light and sternlight.
Rule 24(c), pushing ahead or towing alongside: International shows two masthead lights in a vertical line, sidelights, and a sternlight. Inland shows two masthead lights, sidelights, and two towing lights (yellow) in a vertical line instead of a white sternlight. On the Western Rivers (except below the Huey P. Long Bridge at mile 106.1 Above Head of Passes on the Mississippi River) and waters specified by the Secretary, Inland Rule 24(j) changes this again: a vessel pushing ahead or towing alongside shows sidelights and two towing lights in a vertical line, with no masthead lights.
Inland Rule 24(f): a vessel being pushed ahead (not part of a composite unit) shows sidelights and a special flashing light at the forward end. The special flashing light is a yellow light flashing 50 to 70 times per minute (Inland Rule 21(g)). It isn't found in the International rules.

Our navigation lights cheat sheet has these side by side.

Practice this on your phone. COLREGS: Rules of the Road has 1,272 questions, 83 diagrams, and spaced repetition. Get the iOS app

Rule 28: Constrained by her draft

International Rule 28 lets a vessel constrained by her draft show three all-round red lights in a vertical line, or a cylinder by day. Inland Rule 28 is reserved, meaning there's no Inland equivalent. If a question says "Inland" and offers three red lights as a draft signal, that's your cue something is off.

Rule 30: Anchoring and moored barges

Inland Rule 30(g) says a vessel under 20 meters at anchor in a special anchorage area designated by the Coast Guard doesn't need to show anchor lights or shapes. Inland Rule 30 also adds lighting requirements for certain moored barges. Neither appears in the International version.

Rule 34: Maneuvering signals (the big one)

This is where most Inland vs International questions live.

International Rule 34(a): when vessels are in sight of one another, a power-driven vessel maneuvering as authorized or required sounds one short blast for "I am altering my course to starboard," two short for "I am altering my course to port," and three short for "I am operating astern propulsion." These signals announce an action, and no reply is required.
Inland Rule 34(a): when power-driven vessels are in sight, meeting or crossing within half a mile, one short blast means "I intend to leave you on my port side," two short means "I intend to leave you on my starboard side," and three short means "I am operating astern propulsion." These signal intent, and the other vessel answers with the same signal if she agrees, or sounds the danger signal if in doubt.
Overtaking (Rule 34(c)): International uses two prolonged plus one short (overtake on your starboard side) and two prolonged plus two short (on your port side), with agreement shown by prolonged, short, prolonged, short. Inland uses one short (overtake on your starboard side) and two short (on your port side), answered with the same signal.
Light signals (Rule 34(b)): International uses an all-round white light visible at least 5 miles. Inland allows an all-round white or yellow light visible at least 2 miles, synchronized with the whistle.
Inland extras: Rule 34(g) requires one prolonged blast when a power-driven vessel leaves a dock or berth. Rule 34(h) says vessels that reach agreement by radiotelephone aren't obliged to sound the whistle signals, though they may.

The sound signals guide has a full table.

Rule 35: Fog signals in special anchorage areas

Inland Rule 35(l) says a vessel under 20 meters, or a barge, canal boat, scow, or other nondescript craft, anchored in a special anchorage area designated by the Coast Guard, doesn't need to sound the anchor bell signal.

A study method that works

Label the waters first. Before you think about the scenario, circle "Inland," "International," or "both."
Keep a distinction list. Every time a miss turns on an Inland vs International difference, write down the rule number and the one fact that changed the answer.
Compare side by side. Read the Inland and International versions of Rules 9, 14, 15, 24, and 34 next to each other until you can explain the difference out loud.
Return to mixed practice. Once the differences are clear on their own, shuffle questions so you have to spot the waters from the scenario.

Ready for exam-style practice? Drill your weak spots with missed-question review in COLREGS: Rules of the Road for iPhone and iPad. Download on the App Store

Frequently asked questions

Are the Inland and International rules numbered the same?

Yes. Both run from Rule 1 to Rule 38 with the same topics. A few Inland rules add paragraphs, and Inland Rule 28 is reserved.

What's the biggest difference between Inland and International rules?

Rule 34. International whistle signals announce a maneuver you're making, while Inland signals propose a passing that the other vessel agrees to.

Where is the line between Inland and International waters?

The COLREGS Demarcation Lines in 33 CFR Part 80 mark the boundary. Inside the lines, the Inland Rules apply.

Where can I read the official text?

The U.S. Coast Guard Navigation Center (navcen.uscg.gov) publishes both rule sets side by side, and 33 CFR Part 83 on ecfr.gov holds the Inland Rules.

Mini quiz: test yourself

Under Inland rules, you hear one short blast from a power-driven vessel meeting you within half a mile. What does it mean?
Under International rules, what does one short blast mean?
Does Inland have a rule for vessels constrained by their draft?
What light does Inland Rule 24 require at the forward end of a barge pushed ahead?
On the Western Rivers, who has the right-of-way: a power-driven vessel downbound with a following current, or one upbound?

Answers: 1) "I intend to leave you on my port side," and you answer with one short blast if you agree (Inland Rule 34(a)). 2) "I am altering my course to starboard" (International Rule 34(a)). 3) No. Inland Rule 28 is reserved. 4) Sidelights plus a special flashing light (Inland Rule 24(f)). 5) The downbound vessel with a following current (Inland Rules 9(a)(ii) and 14(d)).