Inland Rules vs International COLREGs — Side by Side
The US Inland Navigation Rules (33 CFR Part 83) parallel the international COLREGs almost word-for-word. The differences are concentrated in five rules and matter most on the OUPV Near-Coastal exam.
TL;DR
Inland and COLREGs are ~95% identical. The five rules where they meaningfully diverge are 9 (narrow channels), 10 (VTS vs TSS), 24 (towing on Western Rivers), 28 (no Inland constrained-by-draft), and 34 (intent vs action signals).
| Feature | Inland Rules (33 CFR Part 83) | COLREGs (International) |
|---|---|---|
| Where it applies | Inside the demarcation lines (33 CFR Part 80) — bays, sounds, Great Lakes, Western Rivers | On the high seas and seaward of the demarcation lines |
| Rule 9 — Narrow Channels | Adds descending-current right-of-way for power-driven vessels on Great Lakes / Western Rivers | Standard 'keep to your starboard side' with no descending-current exception |
| Rule 10 | Vessel Traffic Services (VTS) — must comply with USCG-regulated VTS | Traffic Separation Schemes (TSS) — IMO-adopted lanes |
| Rule 24 — Towing | Special provisions for composite units and Western Rivers towing astern | Standard tow-light progression by tow length |
| Rule 28 — Constrained by Draft | Does not exist — Inland numbering jumps from 27 to 29 | CBD vessels may show three vertical red all-round lights |
| Rule 34 — Manoeuvring Signals | Signals of INTENT — 1 short = 'I intend to leave you on my port side'. Vessels must agree before manoeuvring. | Signals of ACTION — 1 short = 'I am altering course to starboard'. |
| Exam version | Tested on OUPV Inland and Master Inland | Tested on OUPV Near-Coastal and Master Near-Coastal |
Bottom line
If you're studying for OUPV Inland, focus on the Inland Rules and the Western Rivers / Great Lakes deviations. If you're going Near-Coastal, learn both — the demarcation lines mean you'll cross between them on the same trip.