Primary sources
Checked against the current public rule corpus on .
- 33 CFR Part 83 — Inland Navigation Rules (eCFR current issue) (retrieved 2026-05-23)
- 33 CFR Part 80 — COLREGS Demarcation Lines (eCFR current issue) (retrieved 2026-05-23)
- USCG Navigation Center — International and Inland Navigation Rules (Amalgamated) (retrieved 2026-05-23)
- IMO — Convention on the International Regulations for Preventing Collisions at Sea, 1972 (COLREGs) (retrieved 2026-05-23)
Where Inland diverges from COLREGs#
Five rules carry exam-relevant differences. Read each pair together — see the full side-by-side comparison for the rest. Sound-signal questions are the common trap: study COLREGs Rule 34 maneuvering and warning signals before comparing the Inland intent-signal version.
- Rule 9
Inland adds descending-current right of way on Great Lakes / Western Rivers
- Rule 10
Inland covers Vessel Traffic Services (VTS) instead of Traffic Separation Schemes
- Rule 24
Inland adds composite-unit and Western Rivers towing-astern provisions
- Rule 34
Inland signals are intent (must agree); COLREGs signals are action
- Rule 28
No Inland counterpart — constrained-by-draft is COLREGs-only (Inland skips 27 → 29). See COLREGs Rule 28.
Start with the collision-avoidance sequence#
Read these five rules as a set before working through the full directory.
- Rule 5Look-out
- Rule 6Safe Speed
- Rule 7Risk of Collision
- Rule 8Action to Avoid Collision
- Rule 9Narrow Channels
Ready to test yourself? Work the free Rules of the Road practice questions — no sign-in, citation-backed against 33 CFR Part 83 and the COLREGs — or browse practice questions for every exam module.
Keep the rulebook vocabulary close as you study: review COLREGs, demarcation lines, the duties of a give-way vessel and a stand-on vessel, and the Rule 13 definition of overtaking.
All 38 COLREGs Rules by Part#
The complete directory, Parts A–E. Each rule links to its summary, exam-frequency notes, and the Inland parallel.
Part A — General
Rules 1-3: application, responsibility, definitions.
Part B-I — Conduct in Any Visibility
Rules 4-10: lookout, safe speed, risk of collision, action, narrow channels, separation schemes.
Part B-II — In Sight of One Another
Rules 11-18: sailing vessels, overtaking, head-on, crossing, action by give-way / stand-on, responsibilities between vessels.
Part B-III — Restricted Visibility
Rule 19: conduct in fog, snow, heavy rain.
Part C — Lights and Shapes
Rules 20-31: visibility, definitions, and per-vessel-type light displays.
- 20Application (Lights and Shapes)
- 21Definitions (Lights)
- 22Visibility of Lights
- 23Power-driven Vessel Underway
- 24Towing and Pushing
- 25Sailing Vessels Underway and Vessels Under Oars
- 26Fishing Vessels
- 27Vessels Not Under Command or Restricted in Their Ability to Maneuver
- 28Vessels Constrained by Their Draft
- 29Pilot Vessels
- 30Anchored Vessels and Vessels Aground
- 31Seaplanes
Part D — Sound and Light Signals
Rules 32-37: equipment, maneuvering, restricted-visibility, distress signals.
Part E — Exemptions
Rule 38: phase-in exemptions for rule changes.
Frequently asked#
How many COLREGs rules are there?
38 navigation Rules (Parts A–E) grouped into five parts (A through E), plus four annexes covering technical light, shape, and equipment specs. (The full convention has 41 Rules in six Parts; Part F, Rules 39–41, added in 2016, covers verification of compliance and is not a navigation rule or tested.) The US Inland Navigation Rules in 33 CFR Part 83 carry 37 rules — Inland skips Rule 28 (constrained by draft).
What does COLREGs stand for?
The 1972 Convention on the International Regulations for Preventing Collisions at Sea. The acronym is sometimes written COLREGS or COLREG; all refer to the same IMO treaty.
Where do COLREGs apply versus the Inland Rules?
COLREGs apply on the high seas and all connected navigable waters outside the COLREGS demarcation lines fixed by 33 CFR Part 80. Inside those lines — most US harbors, bays, and Western Rivers — 33 CFR Part 83 (the Inland Navigation Rules) controls. The same vessel can be subject to both rule sets on a single transit.
Which COLREGs rules show up most on the USCG license exam?
Rules 5-9 (lookout, safe speed, risk of collision, action to avoid, narrow channels) anchor the collision-avoidance sequence. Rules 13-15 (overtaking, head-on, crossing) and Rule 18 (responsibilities between vessels) drive most situation questions. Rules 23-30 (lights and shapes) and Rule 34 (maneuvering and warning sound signals) carry the highest single-rule question density on the Rules of the Road module.
Are COLREGs and the Inland Rules really the same?
Mostly. The Inland Rules mirror COLREGs almost verbatim with five exam-relevant divergences (Rules 9, 10, 24, 28, and 34) plus Western-Rivers and Great-Lakes-specific provisions. The /vs/inland-vs-international-rules page lists each line-by-line difference.