COLREGS Rule 24 — Towing and Pushing

Rule Text

What it means on the water

• →Towing astern: 2 forward masthead lights (3 if tow > 200m) + sidelights + sternlight + yellow towing light.
• →Pushing ahead or towing alongside: 2 forward masthead lights + sidelights + sternlight (no yellow towing light).
• →Tow > 200m: diamond shape by day on BOTH the towing vessel and the vessel being towed.
• →Vessel being towed astern: sidelights + sternlight (+ diamond if tow > 200m).
• →Vessel being pushed ahead: sidelights at the forward end only.
• →Yellow towing light is in addition to (not replacing) the sternlight when towing astern.

Common exam mistakes

• ✗Thinking the yellow towing light replaces the sternlight — it is shown ABOVE the sternlight, not in place of it.
• ✗Forgetting that pushing ahead requires 2 masthead lights forward, not 1.
• ✗Missing the diamond dayshape when tow exceeds 200m.
• ✗Applying the 3-masthead-light rule to all towing situations — 3 lights are only required when the tow exceeds 200m.

USCG exam questions — Rule 24

These questions are drawn from the same pool used in real USCG licensing exams. Correct answers and explanations are shown.

1. 1. A power-driven vessel towing another vessel where the length of tow exceeds 200 meters shall show how many masthead lights forward?

   • A.One
   • B.Two
   • C.Three✓
   • D.Four

   Why: Rule 24(a)(i) requires three masthead lights in a vertical line forward when the length of tow (from stern of towing vessel to stern of last vessel towed) exceeds 200 meters. Two masthead lights are shown when the tow is 200 meters or less.

2. 2. A vessel towing another astern where the tow does NOT exceed 200 meters shall show, in addition to sidelights and a sternlight:

   • A.Three masthead lights in a vertical line and a yellow towing light
   • B.One masthead light and a yellow towing light above the sternlight
   • C.Two masthead lights in a vertical line only
   • D.Two masthead lights in a vertical line and a yellow towing light above the sternlight✓

   Why: Rule 24(a) prescribes two masthead lights in a vertical line (forward), sidelights, sternlight, and a yellow towing light in a vertical line above the sternlight for tows of 200 meters or less. The yellow towing light distinguishes the tug from a vessel merely underway.

3. 3. A vessel being TOWED astern at night shall show:

   • A.An all-round white light
   • B.A yellow flashing light
   • C.Sidelights and a sternlight only✓
   • D.Sidelights, a sternlight, and a white masthead light if practicable

   Why: Rule 24(e) requires a vessel being towed to show sidelights and a sternlight. If the tow is partly submerged or difficult to see, Rule 24(g) requires additional lights or shapes, but the basic towed vessel shows only sidelights and sternlight.

4. 4. You observe a vessel at night displaying three white masthead lights in a vertical line, sidelights, a sternlight, and a yellow light above the sternlight. What does this indicate?

   • A.A vessel pushing a composite unit ahead
   • B.A vessel towing astern with a tow exceeding 200 meters✓
   • C.A vessel not under command
   • D.A vessel restricted in its ability to maneuver

   Why: Three masthead lights in a vertical line forward plus the yellow towing light above the sternlight indicates an astern tow where the total length of the tow exceeds 200 meters. This combination is a warning to give the vessel and its long tow a wide berth.

5. 5. During daylight hours, a vessel towing another vessel where the length of tow exceeds 200 meters shall display:

   • A.A black diamond shape
   • B.A black cylinder
   • C.A black diamond shape forward and one on the towed vessel✓
   • D.A black cone, point downward

   Why: When the length of the tow exceeds 200 meters, Rule 24(a)(v) requires the towing vessel to display a diamond shape where it can best be seen, and Rule 24(e)(iii) requires the vessel being towed to display a diamond shape as well. This alerts other vessels to the extended hazard of the long tow.

6. 6. A composite unit — a pushing vessel and vessel being pushed that are connected as a rigid unit — shall be regarded as:

   • A.A vessel towing, showing two masthead lights and a yellow towing light
   • B.A power-driven vessel underway, showing the lights prescribed by Rule 23✓
   • C.A RAM vessel, showing red-white-red lights
   • D.A vessel restricted in ability to maneuver, showing ball-diamond-ball shapes

   Why: Rule 24(b)(ii) specifies that when a pushing vessel and a vessel being pushed are rigidly connected as a composite unit, they shall be regarded as a power-driven vessel and show the lights prescribed by Rule 23. This treats the integrated unit as a single entity.

7. 7. A vessel being towed astern at night shall exhibit which lights?

   • A.Sidelights and a stern light✓
   • B.Sidelights, a stern light, and an all-round white light
   • C.A stern light only
   • D.Sidelights only

   Why: Rule 24(e) states that a vessel being towed shall exhibit sidelights and a stern light, the same lights as a power-driven vessel making way but without any masthead lights, clearly indicating its towed status.

8. 8. A power-driven vessel pushing ahead or towing alongside at night shall exhibit which lights forward?

   • A.Two masthead lights in a vertical line forward✓
   • B.Three masthead lights in a vertical line forward
   • C.One masthead light forward
   • D.Two masthead lights arranged horizontally forward

   Why: Under Rule 24(c)(i) (COLREGS / 33 CFR 83.24(c)), a power-driven vessel pushing ahead or towing alongside (other than a composite unit) shows two masthead lights in a vertical line forward, in lieu of the single masthead light of a free-running power-driven vessel. It also carries sidelights and a sternlight (internationally) — under US Inland two towing lights in a vertical line stand in for the sternlight — so the configuration does include a sternlight or its towing-light substitute.

Frequently asked questions

What lights does a vessel towing astern show under COLREGS?

A vessel towing astern shows two white masthead lights in a vertical line forward (three if the tow exceeds 200 meters), port and starboard sidelights, a white sternlight, and a yellow towing light positioned above the sternlight. During the day, a diamond shape is shown when the tow exceeds 200 meters.

What is the difference in lights between towing astern and pushing ahead?

When towing astern, the vessel shows a yellow towing light in addition to the sternlight. When pushing ahead or towing alongside, there is no yellow towing light — just two masthead lights in a vertical line, sidelights, and a sternlight. Both configurations require two masthead lights regardless of vessel length.

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