COLREGs Rule 27: Lights and shapes for vessels not under command or restricted

Last reviewed: October 14, 2026

Rule 27 sets the lights and shapes shown by vessels not under command and vessels restricted in their ability to maneuver. It covers towing, dredging, underwater work, diving and mine clearance. The International and Inland rules differ on towing and on dredge pipelines.

Applies toIt applies to vessels not under command and vessels restricted in their ability to maneuver, including those towing, dredging, diving or clearing mines.

What it says

  1. A vessel not under command must show two all-round red lights in a vertical line where they can best be seen.

    COLREGs Rule 27(a)(i)“two all-round red lights in a vertical line where they can best be seen;”

  2. A vessel restricted in her ability to maneuver, except one engaged in mine clearance operations, must show three all-round lights in a vertical line. The highest and lowest are red and the middle one is white.

    COLREGs Rule 27(b)(i)“The highest and lowest of these lights shall be red and the middle light shall be white;”

  3. International: A power-driven vessel in a towing operation that severely restricts the tow and towing vessel in deviating from course must show the lights or shapes of paragraphs (b)(i) and (ii), in addition to those in Rule 24(a).

    COLREGs Rule 27(c)“shall, in addition to the lights or shapes prescribed in Rule 24(a), exhibit the lights or shapes prescribed in subparagraphs (b)(i) and (ii) of this Rule.”

  4. A vessel dredging or doing underwater operations, when restricted in her ability to maneuver and an obstruction exists, must show two all-round red lights or two balls on the obstructed side. It must show two all-round green lights or two diamonds on the side where another vessel may pass.

    COLREGs Rule 27(d)(ii)“two all-round green lights or two diamonds in a vertical line to indicate the side on which another vessel may pass;”

  5. Inland: Floating dredge pipelines, or those supported on trestles, must show one row of yellow lights at night and in periods of restricted visibility.

    COLREGs Rule 27(d)(iv)“Dredge pipelines that are floating or supported on trestles shall display the following lights at night and in periods of restricted visibility.”

  6. A vessel engaged in mine clearance operations must show three all-round green lights or three balls. These show it is dangerous for another vessel to approach within 1000 meters.

    COLREGs Rule 27(f)“These lights or shapes indicate that it is dangerous for another vessel to approach within 1000 meters of the mine clearance vessel.”

  7. International: Vessels of less than 12 meters in length, except those engaged in diving operations, are not required to exhibit the lights and shapes of this Rule.

    COLREGs Rule 27(g)“Vessels of less than 12 meters in length, except those engaged in diving operations, shall not be required to exhibit the lights and shapes prescribed in this Rule.”

Common questions

What lights must a vessel not under command show?

It must show two all-round red lights in a vertical line where they can best be seen. When making way through the water, it must also show sidelights and a sternlight.

“two all-round red lights in a vertical line where they can best be seen;”

Are the signals in Rule 27 distress signals?

No. The signals in this Rule are not signals of vessels in distress and requiring assistance. Such signals are contained in Annex IV.

“The signals prescribed in this Rule are not signals of vessels in distress and requiring assistance.”

What does a small diving vessel show under Rule 27?

When size makes it impracticable to show all the paragraph (d) lights and shapes, it shows three all-round lights in a vertical line. It also shows a rigid replica of International Code flag "A" not less than 1 meter in height.

“a rigid replica of the International Code flag “A” not less than 1 meter in height.”

The text of COLREGs Rule 27

U.S. Coast Guard, Navigation Rules and Regulations Handbook

Rule 27: Vessels Not Under Command or Restricted in Their

International (COLREGs)

Ability to Maneuver

(a) 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 through the water, in addition to the lights prescribed in this paragraph, sidelights and a sternlight. Vessel not under command—not making way. Same for Inland.

(b) A vessel restricted in her ability to maneuver, except a vessel engaged in mine clearance operations, shall exhibit:

(i) three all-round lights in a vertical line where they can best be seen. The highest and lowest of these lights shall be red and the middle light shall be white;

(ii) three shapes in a vertical line where they can best be seen. The highest and lowest of these shapes shall be balls and the middle one a diamond;

(iii) when making way through the water, a masthead light or lights, sidelights and a sternlight, in addition to the lights prescribed in subparagraph (i);

(iv) when at anchor, in addition to the lights or shapes prescribed in subparagraphs (i) and (ii), the light, lights or shape prescribed in Rule 30. Vessel restricted in her ability to maneuver—making way; vessel less than 50 meters in length. Same for Inland.

(c) 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 prescribed in subparagraphs (b)(i) and (ii) of this Rule.

(d) A vessel engaged in dredging or underwater operations, when restricted in her ability to maneuver, shall exhibit the lights and shapes prescribed in subparagraphs (b)(i), (ii) and (iii) of this Rule 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 prescribed in this paragraph instead of the lights or shape prescribed in Rule 30. Vessel engaged in dredging or underwater operations when restricted in ability to maneuver—making way with an obstruction on the starboard side. Same for Inland. Vessel engaged in dredging or underwater operations when restricted in ability to maneuver—not making way with an obstruction on the starboard side. Same for Inland.

(e) Whenever the size of a vessel engaged in diving operations makes it impracticable to exhibit all lights and shapes prescribed in paragraph (d) of this Rule, the following shall be exhibited:

(i) three all-round lights in a vertical line where they can best be seen. The highest and lowest of these lights shall be red and the middle light shall be white;

(ii) a rigid replica of the International Code flag “A” not less than 1 meter in height. Measures shall be taken to ensure its all-round visibility. Small vessel engaged in diving operations by day. Same for Inland.

(f) 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 of these lights or shapes shall be exhibited near the foremast head and one at each end of the fore yard. These lights or shapes indicate that it is dangerous for another vessel to approach within 1000 meters of the mine clearance vessel. Vessel engaged in mine clearance operations—vessel less than 50 meters in length. Same for Inland.

(g) Vessels of less than 12 meters in length, except those engaged in diving operations, shall not be required to exhibit the lights and shapes prescribed in this Rule.

(h) The signals prescribed in this Rule are not signals of vessels in distress and requiring assistance. Such signals are contained in Annex IV to these Regulations.

Inland Rules

Vessels not under command or restricted in their ability to maneuver

(a) 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; and

(iii) When making way through the water, in addition to the lights prescribed in this paragraph, sidelights and a sternlight. Vessel not under command—making way. Same for International.

(b) A vessel restricted in her ability to maneuver, except a vessel engaged in mine clearance operations, shall exhibit:

(i) Three all-round lights in a vertical line where they can best be seen. The highest and lowest of these lights shall be red and the middle light shall be white;

(ii) Three shapes in a vertical line where they can best be seen. The highest and lowest of these shapes shall be balls and the middle one a diamond;

(iii) When making way through the water, a masthead light or lights, sidelights and a sternlight, in addition to the lights prescribed in paragraph

(b)(i) of this Rule; and

(iv) When at anchor, in addition to the lights or shapes prescribed in paragraphs (b)(i) and (ii), the light, lights or shapes prescribed in Rule 30

(§ 83.30). Vessel restricted in her ability to maneuver—at anchor; vessel less than 50 meters in length. Same for International.

(c) A vessel engaged in a towing operation which 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 subparagraphs (b)(i) and (ii) of this Rule, exhibit the lights or shape prescribed in Rule 24 (§ 83.24). Vessel engaged in towing operation which severely restricts towing vessel and her tow in their ability to deviate from their course—length of tow does not exceed 200 meters; towing vessel less than 50 meters in length. Same for International.

(d) A vessel engaged in dredging or underwater operations, when restricted in her ability to maneuver, shall exhibit the lights and shapes prescribed in subparagraphs (b)(i), (ii), and (iii) of this Rule 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; and

(iii) When at anchor, the lights or shape prescribed by this paragraph, instead of the lights or shape prescribed in Rule 30 (§ 83.30).

(iv) Dredge pipelines that are floating or supported on trestles shall display the following lights at night and in periods of restricted visibility.

(1) One row of yellow lights. The lights must be:

(A) Flashing 50 to 70 times per minute,

(B) Visible all round the horizon,

(C) Visible for at least 2 miles,

(D) Not less than 1 and not more than 3.5 meters above the water,

(E) Approximately equally spaced, and

(F) Not more than 10 meters apart where the pipeline crosses a navigable channel. Where the pipeline does not cross a navigable channel the lights must be sufficient in number to clearly show the pipeline’s length and course.

(2) Two red lights at each end of the pipeline, including the ends in a channel where the pipeline is separated to allow vessels to pass (whether open or closed). The lights must be:

(A) Visible all round the horizon, and

(B) Visible for at least 2 miles, and

(C) One meter apart in a vertical line with the lower light at the same height above the water as the flashing yellow light.

(e) Whenever the size of a vessel engaged in diving operations makes it impracticable to exhibit all lights and shapes prescribed in paragraph (d) of this Rule, as appropriate, the following shall instead be exhibited:

(i) Three all-round lights in a vertical line where they can best be seen. The highest and lowest of these lights shall be red and the middle light shall be white;

(ii) A rigid replica of the International Code flag “A” not less than 1 meter in height. Measures shall be taken to ensure its all-round visibility. Small vessel engaged in diving operations at night or in restricted visibility. Same for International.

(f) A vessel engaged in mine clearance operations shall, in addition to the lights prescribed for a power-driven vessel in Rule 23 (§ 83.23) or to the lights or shape prescribed for a vessel at anchor in Rule 30 (§ 83.30), as appropriate, exhibit three all-round green lights or three balls. One of these lights or shapes shall be exhibited near the foremast head and one at each end of the fore yard. These lights or shapes indicate that it is dangerous for another vessel to approach within 1000 meters of the mine clearance vessel. Vessel engaged in mine clearance operations. Same for International.

(g) A vessel of less than 12 meters in length, except when engaged in diving operations, is not required to exhibit the lights or shapes prescribed in this Rule.

(h) The signals prescribed in this Rule are not signals of vessels in distress and requiring assistance. Such signals are contained in Annex IV to these Rules (33 CFR part 87).

Sections it refers to

The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of August 12, 2024. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.