Comparisons
COLREG (International) vs US Inland — major differences
Comparison study notes and reference passages. Read the linked complete rules, including qualifications, exceptions and any publication notes; translated study text is not an official instrument.
US applicability is determined by the COLREG Demarcation Lines in 33 CFR 80 and the scope of 33 CFR 83. Consult the applicable chart and rules; do not invent a rule for a vessel exactly on a boundary.
Check the current examination module and licence requirements. The USCG publishes International and Inland rules together; this comparison covers selected differences and is not an exhaustive examination syllabus.
COLREG (International) vs US Inland — major differences
| Topic | COLREG (International) | US Inland Rules |
|---|---|---|
| 1 / 33 CFR 80, 83 | (a) These Rules shall apply to all vessels upon the high seas and in all waters connected therewith navigable by seagoing vessels. | US applicability is determined by the COLREG Demarcation Lines in 33 CFR 80 and the scope of 33 CFR 83. Consult the applicable chart and rules; do not invent a rule for a vessel exactly on a boundary. US Great Lakes waters use US Inland Rules. Canadian waters are governed by Canadian Collision Regulations, which implement COLREG with Canadian modifications. Do not apply US Inland Rules to the entire binational lake system. |
| 24(f) | (f) Provided that any number of vessels being towed alongside or pushed in a group shall be lighted as one vessel: (i) a vessel being pushed ahead, not being part of a composite unit, shall exhibit at the forward end, sidelights; (ii) a vessel being towed alongside shall exhibit a sternlight and at the forward end, sidelights. | Inland Rule 24(f): the vessel BEING pushed ahead, outside a composite unit, or BEING towed alongside shows the special flashing yellow light forward. It is not a universal light on the pushing/towing vessel. Groups and towing on both sides have specific arrangements. |
| 34(a) | (a) When vessels are in sight of one another, a power-driven vessel underway, when maneuvering as authorized or required by these Rules, shall indicate that maneuver by the following signals on her whistle: − one short blast to mean “I am altering my course to starboard”; − two short blasts to mean “I am altering my course to port”; − three short blasts to mean “I am operating astern propulsion”. | Inland Rule 34(a): power-driven vessels in sight, meeting or crossing within half a mile, use one short for intended port-to-port passing and two for starboard-to-starboard; agreement is answered with the same signal. Three short still means operating astern propulsion. Rule 34(h) covers radiotelephone agreement. |
| 34(g) Inland | — | Inland Rule 34(g): a power-driven vessel leaving a dock or berth sounds ONE PROLONGED blast. Five or more short rapid blasts remain the doubt/danger signal, not the departure signal. |
| 30(e) / 30(g) Inland | (e) A vessel of less than 7 meters in length, when at anchor, not in or near a narrow channel, fairway or anchorage, or where other vessels normally navigate, shall not be required to exhibit the lights or shape prescribed in paragraphs (a) and (b) of this Rule. | Inland Rule 30(g): vessels under 20 m anchored in a Coast Guard-designated special anchorage area are exempt from the anchor lights and shapes required by that rule. International Rule 30(e) instead has its own under-7 m location-qualified exemption. |
33 CFR 80 · 83
US applicability is determined by the COLREG Demarcation Lines in 33 CFR 80 and the scope of 33 CFR 83. Consult the applicable chart and rules; do not invent a rule for a vessel exactly on a boundary.
- Inland Rule 24(f): the vessel BEING pushed ahead, outside a composite unit, or BEING towed alongside shows the special flashing yellow light forward. It is not a universal light on the pushing/towing vessel. Groups and towing on both sides have specific arrangements.
- Inland Rule 34(a): power-driven vessels in sight, meeting or crossing within half a mile, use one short for intended port-to-port passing and two for starboard-to-starboard; agreement is answered with the same signal. Three short still means operating astern propulsion. Rule 34(h) covers radiotelephone agreement.
- Inland Rule 34(g): a power-driven vessel leaving a dock or berth sounds ONE PROLONGED blast. Five or more short rapid blasts remain the doubt/danger signal, not the departure signal.
- US Great Lakes waters use US Inland Rules. Canadian waters are governed by Canadian Collision Regulations, which implement COLREG with Canadian modifications. Do not apply US Inland Rules to the entire binational lake system.
Drill the rules that actually differ
Frequently asked questions
Where do the US Inland Rules apply?
US applicability is determined by the COLREG Demarcation Lines in 33 CFR 80 and the scope of 33 CFR 83. Consult the applicable chart and rules; do not invent a rule for a vessel exactly on a boundary.
Why does Inland have a yellow flashing light?
Inland Rule 24(f): the vessel BEING pushed ahead, outside a composite unit, or BEING towed alongside shows the special flashing yellow light forward. It is not a universal light on the pushing/towing vessel. Groups and towing on both sides have specific arrangements.
Are the whistle signals the same in COLREG and US Inland Rules?
(a) When vessels are in sight of one another, a power-driven vessel underway, when maneuvering as authorized or required by these Rules, shall indicate that maneuver by the following signals on her whistle:
− one short blast to mean “I am altering my course to starboard”;
− two short blasts to mean “I am altering my course to port”;
− three short blasts to mean “I am operating astern propulsion”. Inland Rule 34(a): power-driven vessels in sight, meeting or crossing within half a mile, use one short for intended port-to-port passing and two for starboard-to-starboard; agreement is answered with the same signal. Three short still means operating astern propulsion. Rule 34(h) covers radiotelephone agreement.
Do USCG candidates have to learn both rule sets?
Check the current examination module and licence requirements. The USCG publishes International and Inland rules together; this comparison covers selected differences and is not an exhaustive examination syllabus.
Do COLREG Rules apply on the Great Lakes?
US Great Lakes waters use US Inland Rules. Canadian waters are governed by Canadian Collision Regulations, which implement COLREG with Canadian modifications. Do not apply US Inland Rules to the entire binational lake system.
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