COLREGs Rule 20: Application of lights and shapes rules

Last reviewed: October 14, 2026

Rule 20 sets when the lights and shapes rules apply. The rules must be complied with in all weathers, the lights rules from sunset to sunrise and the shapes rules by day. The Inland rule adds that a vessel's lights and shapes may be lowered to pass under a bridge.

What it says

  1. International: Rules in this part must be complied with in all weathers.

    COLREGs Rule 20(a)“Rules in this part shall be complied with in all weathers.”

  2. Inland: Rules in this subpart (Rules 20-31) must be complied with in all weathers.

    COLREGs Rule 20(a)“Rules in this subpart (Rules 20-31) (§§ 83.20 through 83.31) shall be complied with in all weathers.”

  3. The rules concerning lights must be complied with from sunset to sunrise. During those times no other lights may be exhibited, except lights that cannot be mistaken for the specified lights, or do not impair their visibility or distinctive character, or interfere with the keeping of a proper look-out.

    COLREGs Rule 20(b)“no other lights shall be exhibited, except such lights as cannot be mistaken for the lights specified in these Rules or do not impair their visibility or distinctive character”

  4. Prescribed lights, if carried, must also be exhibited from sunrise to sunset in restricted visibility. They may be exhibited in all other circumstances when it is deemed necessary.

    COLREGs Rule 20(c)“The lights prescribed by these Rules shall, if carried, also be exhibited from sunrise to sunset in restricted visibility”

  5. The rules concerning shapes must be complied with by day.

    COLREGs Rule 20(d)“The Rules concerning shapes shall be complied with by day.”

  6. International: Lights and shapes must comply with the provisions of Annex I to these Regulations.

    COLREGs Rule 20(e)“The lights and shapes specified in these Rules shall comply with the provisions of Annex I to these Regulations.”

  7. Inland: A vessel's navigation lights and shapes may be lowered if necessary to pass under a bridge.

    COLREGs Rule 20(f)“A vessel’s navigation lights and shapes may be lowered if necessary to pass under a bridge.”

Common questions

When must navigation lights be shown?

The rules concerning lights must be complied with from sunset to sunrise. Lights, if carried, must also be exhibited from sunrise to sunset in restricted visibility.

“The lights prescribed by these Rules shall, if carried, also be exhibited from sunrise to sunset in restricted visibility”

When must day shapes be displayed?

The rules concerning shapes must be complied with by day.

“The Rules concerning shapes shall be complied with by day.”

Can I lower my navigation lights to pass under a bridge?

Inland: Yes. A vessel's navigation lights and shapes may be lowered if necessary to pass under a bridge. The International text has no such provision.

“A vessel’s navigation lights and shapes may be lowered if necessary to pass under a bridge.”

Do the lights and shapes rules apply in bad weather?

Yes. International: rules in this part must be complied with in all weathers.

“Rules in this part shall be complied with in all weathers.”

The text of COLREGs Rule 20

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

Rule 20: Application

International (COLREGs)

(a) Rules in this part shall be complied with in all weathers. (b) The Rules concerning lights shall be complied with from sunset to sunrise, and during such times no other lights shall be exhibited, except such lights as cannot be mistaken for the lights specified in these Rules or do not impair their visibility or distinctive character, or interfere with the keeping of a proper look- out. (c) The lights prescribed by these Rules shall, if carried, also be exhibited from sunrise to sunset in restricted visibility and may be exhibited in all other circumstances when it is deemed necessary. (d) The Rules concerning shapes shall be complied with by day. (e) The lights and shapes specified in these Rules shall comply with the provisions of Annex I to these Regulations.

Inland Rules

Application (a) Rules in this subpart (Rules 20-31) (§§ 83.20 through 83.31) shall be complied with in all weathers. (b) The Rules concerning lights (§§ 83.20 through 83.31) shall be complied with from sunset to sunrise, and during such times no other lights shall be exhibited, except such lights as cannot be mistaken for the lights specified in these Rules or do not impair their visibility or distinctive character, or interfere with the keeping of a proper look-out. (c) The lights prescribed by these Rules shall, if carried, also be exhibited from sunrise to sunset in restricted visibility and may be exhibited in all other circumstances when it is deemed necessary. (d) The Rules concerning shapes shall be complied with by day. (e) The lights and shapes specified in these Rules shall comply with the provisions of Annex I of these Rules (33 CFR Part 84). (f) A vessel’s navigation lights and shapes may be lowered if necessary to pass under a bridge.

Sections it refers to

  • 33 CFR Part 84

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.