COLREGS Rule 24 — Navigation Lights
Towing and Pushing Vessel — Navigation Lights (COLREGS Rule 24)
A vessel towing astern shows two forward masthead lights in a vertical line (three if the tow exceeds 200 meters), sidelights, a white sternlight, and a yellow towing light positioned directly above the sternlight. Pushing ahead or towing alongside uses two masthead lights but no yellow towing light. Tows over 200 meters require a diamond dayshape on both vessels.
Condition: Underway while towing astern, pushing ahead, or towing alongside
Navigation lights required
| Light | Color | Arc | Position |
|---|---|---|---|
| Forward masthead lights (towing astern) | White | 225° each | Two vertical in line forward (three if tow > 200 m) |
| Port sidelight | Red | 112.5° | Port side |
| Starboard sidelight | Green | 112.5° | Starboard side |
| Sternlight | White | 135° | Stern, centerline |
| Towing light (towing astern only) | Yellow | 135° | Stern, directly above the sternlight |
| Forward masthead lights (pushing ahead or towing alongside) | White | 225° each | Two vertical in line forward |
Forward masthead lights (towing astern): Two lights = tow 200 m or less; three lights = tow more than 200 m
Towing light (towing astern only): Shown in addition to — NOT instead of — the white sternlight. Only used when towing astern, not when pushing ahead or towing alongside.
Forward masthead lights (pushing ahead or towing alongside): Two lights always — regardless of tow length. No yellow towing light for pushing or alongside tow.
Dayshapes
| Shape | Position | When displayed |
|---|---|---|
| Diamond | Forward on the towing vessel, where best seen; also on the vessel being towed | When the length of the tow exceeds 200 meters — required on BOTH the towing vessel and the towed object |
Exceptions and size rules
- →A vessel being towed astern shows sidelights and a sternlight (plus a diamond if tow > 200 m). It does NOT show masthead lights.
- →A vessel being pushed ahead (not part of a composite unit) shows sidelights at the forward end only.
- →When a vessel is pushed ahead as part of a composite unit, the composite is treated as a single power-driven vessel and shows power-driven vessel lights.
Inland Rules differences
- !Under US Inland Rules, a vessel pushing ahead or towing alongside in a composite unit may show the combined light set as a single power-driven vessel rather than two masthead lights.
Common exam mistakes
- ✗Thinking the yellow towing light replaces the white sternlight — it is shown ABOVE and in addition to the sternlight.
- ✗Giving a pushing vessel a yellow towing light — pushing ahead and towing alongside do NOT use a yellow towing light.
- ✗Applying the three-masthead-light rule to all towing situations — three lights are only required when the tow exceeds 200 meters.
- ✗Forgetting the diamond dayshape is required on BOTH the towing vessel and the towed vessel when the tow exceeds 200 meters.
USCG exam questions — Towing and Pushing Vessel
These questions are drawn from the same pool used in real USCG licensing exams. Correct answers and explanations are shown.
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. 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. 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. 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. 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. 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. 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. 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 is the yellow towing light and when is it used?
- The yellow towing light is a 135° yellow stern light positioned directly above the white sternlight. It is shown only when towing astern — it is not used when pushing ahead or towing alongside. Critically, the yellow towing light is shown IN ADDITION TO the white sternlight, not instead of it.
- How many forward masthead lights does a towing vessel show?
- Two masthead lights in a vertical line when the tow is 200 meters or less, and three masthead lights in a vertical line when the tow exceeds 200 meters. A vessel pushing ahead or towing alongside always shows two masthead lights regardless of tow or push length.
- What lights does the vessel being towed astern show?
- A vessel being towed astern shows sidelights (red port, green starboard) and a white sternlight. It does not show masthead lights. When the tow length exceeds 200 meters, the towed vessel must also display a diamond dayshape by day.
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