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Rule 24: Towing and Pushing (COLREGS)

Last reviewed October 21, 2026

The short answer

Rule 24 says a power-driven vessel towing astern shows two masthead lights in a vertical line (three if the tow exceeds 200 meters), sidelights, a sternlight, and a yellow towing light above the sternlight, plus a diamond by day for long tows. Pushing ahead and towing alongside have their own light sets.

The rule text

When the length of the tow, measuring from the stern of the towing vessel to the after end of the tow, exceeds 200 meters, three such lights in a vertical line;

International Rules, U.S. Coast Guard Navigation Rules and Regulations Handbook (NAVCEN, 2024 corrected edition), Rule 24

a towing light in a vertical line above the sternlight;

International Rules, U.S. Coast Guard Navigation Rules and Regulations Handbook (NAVCEN, 2024 corrected edition), Rule 24

When a pushing vessel and a vessel being pushed ahead are rigidly connected in a composite unit they shall be regarded as a power-driven vessel and exhibit the lights prescribed in Rule 23.

International Rules, U.S. Coast Guard Navigation Rules and Regulations Handbook (NAVCEN, 2024 corrected edition), Rule 24

What it means on the water

  • Towing astern: two masthead lights (three if tow over 200 meters), sidelights, sternlight, towing light above the sternlight, diamond if over 200 meters (24(a)).
  • Composite unit: lit as one power-driven vessel (24(b)).
  • Pushing ahead or alongside: two masthead lights and sidelights, plus a sternlight (International) or two towing lights (Inland) (24(c)).
  • Vessel towed: sidelights, sternlight, diamond if tow over 200 meters (24(e)).
  • Partly submerged objects towed: all-round white lights and a diamond at the after end (24(g)).

International vs Inland

Pushing ahead or towing alongside: International 24(c) shows a sternlight; Inland 24(c) shows two towing lights in a vertical line. Inland 24(f) adds a special flashing light at the forward end of a vessel pushed ahead or towed alongside. Inland 24(j): on the Western Rivers (except below the Huey P. Long Bridge) and specified waters, a vessel pushing ahead or towing alongside shows sidelights and two towing lights, with no masthead lights.

Common exam traps

  • Counting the tow from the tug's bow. It's from the stern of the towing vessel to the after end of the tow.
  • Using two towing lights on an International pusher.
  • Forgetting the Western Rivers exception in Inland 24(j).

Try 3 questions on Rule 24

  1. A tug tows astern with a 150-meter tow. How many masthead lights in a vertical line?

    1. One
    2. Two
    3. Three
    4. Four
    Show answer

    B. Two Rule 24(a)(i).

  2. What day shape shows a tow longer than 200 meters?

    1. Ball
    2. Diamond
    3. Cone
    4. Cylinder
    Show answer

    B. Diamond Rule 24(a)(v).

  3. Inland, pushing ahead (not on the Western Rivers): what's shown instead of a sternlight?

    1. Two towing lights in a vertical line
    2. A special flashing light
    3. Nothing
    4. An all-round white
    Show answer

    A. Two towing lights in a vertical line Inland Rule 24(c)(iii).

Frequently asked questions

What color is a towing light?

Yellow, with the same arc as a sternlight (Rule 21(d)).

How is a composite unit lit?

As one power-driven vessel under Rule 23 (Rule 24(b)).

Do towing lights differ Inland?

Yes for pushing ahead and towing alongside (Inland 24(c), (f), and (j)).

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