COLREGs trainerPart C: Lights and Shapes
Rule 27
NUC: two reds. RAM: red-white-red, plus appropriate shapes.
Wording follows the International Regulations as printed in the US Coast Guard Navigation Rules handbook (2024), with British spelling, and is shortened in places. Download the rules
A vessel not under command shall exhibit: (i) two all-round red lights in a vertical line where they can best be seen; (ii) two balls or similar shapes in a vertical line where they can best be seen; (iii) when making way, sidelights and a sternlight as well.
A vessel restricted in her ability to manoeuvre, except a vessel engaged in mine clearance operations, shall exhibit: (i) three all-round lights in a vertical line: highest and lowest red, middle white; (ii) three shapes in a vertical line: highest and lowest balls, middle a diamond; (iii) when making way, masthead lights, sidelights and a sternlight in addition; (iv) when at anchor, the Rule 30 lights or shapes as well.
A power-driven vessel engaged in a towing operation such as severely restricts the towing vessel and her tow in their ability to deviate from their course shall, in addition to the lights or shapes prescribed in Rule 24(a), exhibit the lights or shapes of paragraph (b)(i) and (ii).
A vessel engaged in dredging or underwater operations, when restricted in her ability to manoeuvre, shall exhibit the lights and shapes of paragraph (b)(i), (ii) and (iii) (so, when making way, masthead lights, sidelights and a sternlight as well) and shall in addition, when an obstruction exists, exhibit: (i) two all-round red lights or two balls in a vertical line to indicate the side on which the obstruction exists; (ii) two all-round green lights or two diamonds in a vertical line to indicate the side on which another vessel may pass; (iii) when at anchor, the lights or shapes of this paragraph instead of the lights or shape prescribed in Rule 30.
Where the size of a vessel engaged in diving operations makes it impracticable to exhibit all the paragraph (d) lights and shapes, she shall exhibit: (i) three all-round lights in a vertical line where they can best be seen, the highest and lowest red and the middle white; (ii) a rigid replica of the International Code flag "A" not less than 1 m in height, with measures taken to ensure its all-round visibility.
A vessel engaged in mine clearance operations shall, in addition to the lights prescribed for a power-driven vessel in Rule 23 or to the lights or shape prescribed for a vessel at anchor in Rule 30 as appropriate, exhibit three all-round green lights or three balls: one near the foremast head and one at each end of the fore yard. They mean it is dangerous for another vessel to approach within 1000 m of the mine clearance vessel.
Vessels of less than 12 m in length, except those engaged in diving operations, are not required to exhibit the lights and shapes prescribed in this Rule.
The signals prescribed in this Rule are not signals of vessels in distress. Distress signals are contained in Annex IV.
A training aid, not the official text. The COLREGs are an IMO convention, and your national authority publishes the version that applies in its waters. Check the rules themselves before you rely on them at sea. Download the rules.