Part C — Lights and Shapes
COLREGS Rule 28 — Vessels Constrained by their Draft
Rule 28 is a COLREGS-only rule — it has no equivalent in the US Inland Rules. A vessel constrained by her draft may show three all-around red lights in a vertical line, or a cylinder by day, in addition to the normal lights of a power-driven vessel.
Rule Text
A vessel constrained by her draft may, in addition to the lights prescribed for power-driven vessels in Rule 23, exhibit where they can best be seen three all-around red lights in a vertical line, or a cylinder. These lights and shapes are not mandatory; they are permissive.
What it means on the water
- →CBD status applies only to POWER-DRIVEN vessels (by definition in Rule 3).
- →COLREGS ONLY — the US Inland Rules have no constrained-by-draft status.
- →The three all-around red lights and cylinder are OPTIONAL (permissive), not mandatory.
- →The CBD lights are shown IN ADDITION TO normal power-driven vessel lights (Rule 23).
- →Three vertical red lights distinguish CBD from NUC (2 red) and RAM (red/white/red).
Common exam mistakes
- ✗Thinking CBD lights are mandatory — they are permissive (a vessel MAY show them).
- ✗Applying CBD status in Inland Rules waters — CBD only exists under COLREGS.
- ✗Confusing three vertical red lights (CBD) with two vertical red lights (NUC).
- ✗Applying CBD to sailing vessels — only power-driven vessels qualify under Rule 3.
USCG exam questions — Rule 28
These questions are drawn from the same pool used in real USCG licensing exams. Correct answers and explanations are shown.
1. A vessel 'constrained by her draft' as defined in Rule 3(h) applies to:
- A.A power-driven vessel which, because of her draft in relation to the available depth and width of navigable water, is severely restricted in her ability to deviate from the course she is following✓
- B.Any vessel whose draft exceeds 10 meters
- C.Any vessel that is heavily laden to the point where her freeboard is less than 0.5 meters
- D.Both power-driven and sailing vessels navigating in charted shallow water areas
Why: Rule 3(h) defines CBD as applying only to power-driven vessels whose draft in relation to available depth severely restricts their ability to deviate from their course — this is a COLREGS-only category not found in the Inland Rules.
2. A vessel constrained by her draft may exhibit which optional lights?
- A.Three all-round red lights in a vertical line✓
- B.Three all-round blue lights in a vertical line
- C.Two all-round red lights in a vertical line
- D.A single all-round red light
Why: Rule 28 allows a power-driven vessel constrained by her draft to optionally exhibit three all-round red lights in a vertical line in addition to prescribed lights, indicating to other vessels that maneuvering ability is severely limited by available water depth.
Frequently asked questions
- What lights does a vessel constrained by her draft show?
- A vessel constrained by draft may show three all-around red lights in a vertical line, or a cylinder by day, in addition to the normal lights of a power-driven vessel under Rule 23. These are permissive — the vessel may show them but is not required to.
- Do the US Inland Rules have a category for vessels constrained by draft?
- No. The constrained-by-draft status exists only under the 72 COLREGS (international rules). When operating under US Inland Rules, there is no equivalent category. This is one of the most commonly tested COLREGS-vs-Inland distinctions.
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