Rule 24 — Towing and Pushing: Light Requirements for the Towing Vessel and the Tow

TL;DR — A power-driven vessel towing astern shows two (or three) masthead lights in a vertical line plus a yellow towing light above the sternlight; pushing ahead or towing alongside substitutes two towing lights in a vertical line for the sternlight, except on Western Rivers where masthead lights are omitted entirely. The tow itself shows sidelights, a sternlight, and — when the tow length exceeds 200 meters — a diamond shape.

---

What the Rule Says

Towing Astern — the Towing Vessel

A power-driven vessel towing astern shall exhibit 33 CFR §83.24:

• Two masthead lights in a vertical line, in place of the single (or second) masthead light otherwise required by Rule 23. When the length of the tow — measured from the stern of the towing vessel to the after end of the tow — exceeds 200 meters, this becomes three masthead lights in a vertical line.
• Sidelights (green starboard, red port).
• A sternlight (white, 135° arc).
• A towing light — a yellow light with the same arc as the sternlight (135°) — carried in a vertical line above the sternlight.
• When tow length exceeds 200 meters, a diamond shape where it can best be seen.

The towing light is defined as a yellow light having the same characteristics as the sternlight. 33 CFR §83.21 The sternlight itself is a white light placed as nearly as practicable at the stern, showing an unbroken light over 135 degrees, fixed to show 67.5 degrees from right aft on each side. 33 CFR §83.21

Pushing Ahead or Towing Alongside — the Towing Vessel

A power-driven vessel pushing ahead or towing alongside (and not forming a rigid composite unit) shall exhibit 33 CFR §83.24:

• Two masthead lights in a vertical line (replacing the Rule 23 masthead light arrangement).
• Sidelights.
• Two towing lights in a vertical line (yellow, 135° arc each) — no sternlight is shown; the two towing lights take its place.

Note that paragraph (d) of Rule 24 requires that a towing vessel to which paragraphs (a) or (c) apply shall also comply with Rule 23(a)(i) and (ii) — meaning the masthead light obligations of Rule 23 remain in force alongside the towing-specific lights. 33 CFR §83.24

Composite Unit Exception

When a pushing vessel and the vessel being pushed ahead are rigidly connected in a composite unit, the combination is treated as a single power-driven vessel and exhibits only the lights prescribed in Rule 23 — no towing lights at all. 33 CFR §83.24

Western Rivers Exception

On the Western Rivers (except below the Huey P. Long Bridge at mile 106.1 Above Head of Passes on the Mississippi River), a power-driven vessel pushing ahead or towing alongside shall exhibit only 33 CFR §83.24:

• Sidelights, and
• Two towing lights in a vertical line.

The two masthead lights required under paragraph (c) are omitted on Western Rivers. This is a significant distinction from the standard inland/international arrangement. The Boatswain's Mate Manual confirms that pushing ahead is the standard towing arrangement on Western Rivers and that light arrangements differ significantly from open-water towing astern. USCG Boatswain Manual Ch. 3 §3.3

Distress-Towing Exception

Where it is impracticable for a vessel not normally engaged in towing to display the prescribed towing lights when assisting a vessel in distress, those lights are not required. All possible measures shall be taken to indicate the nature of the relationship, and the searchlight authorized by Rule 36 may be used to illuminate the tow. 33 CFR §83.24

---

Lights on the Tow Itself

Standard tow (towed astern): The vessel or object being towed shall exhibit 33 CFR §83.24:

• Sidelights;
• A sternlight; and
• When tow length exceeds 200 meters, a diamond shape where it can best be seen.

Vessel pushed ahead (not a composite unit): At the forward end, sidelights and a special flashing light. 33 CFR §83.24

Vessel towed alongside: A sternlight and, at the forward end, sidelights and a special flashing light. 33 CFR §83.24

Multiple vessels towed alongside or pushed in a group are lighted as one vessel, with the exception that when vessels are towed alongside on both sides of the towing vessel, a sternlight shall be exhibited on the stern of the outboard vessel on each side, a single set of sidelights as far forward and outboard as practicable, and a single special flashing light. 33 CFR §83.24

The special flashing light is defined as a yellow light flashing at 50 to 70 flashes per minute, placed as far forward as practicable on the fore and aft centerline of the tow, showing an arc of not less than 180° nor more than 225°, from right ahead to abeam and no more than 22.5° abaft the beam on either side. 33 CFR §83.21

Inconspicuous, partly submerged vessel or object being towed: 33 CFR §83.24

• If less than 25 meters in breadth: one all-round white light at or near each end.
• If 25 meters or more in breadth: four all-round white lights to mark its length and breadth.
• If exceeding 100 meters in length: additional all-round white lights so that spacing does not exceed 100 meters.
• A diamond shape at or near the aftermost extremity.
• The towing vessel may direct a searchlight toward the tow to indicate its presence.

The all-round white lights on an inconspicuous partly submerged tow must be visible at a minimum range of 3 miles, regardless of the size of the towing vessel. 33 CFR §83.22

---

Vertical Spacing of Lights

When two or three lights are carried in a vertical line on a vessel of 20 meters or more in length, they shall be spaced not less than 1 meter apart, and the lowest shall be placed at a height of not less than 4 meters above the hull (except where a towing light is required). On a vessel of less than 20 meters, spacing is not less than 1 meter apart and the lowest not less than 2 meters above the gunwale. When three lights are carried, they shall be equally spaced. 33 CFR §84.02

For towing vessels, one of the two or three masthead lights shall be placed in the same position as either the forward or after masthead light, provided that the lowest after masthead light shall be at least 2 meters vertically higher than the highest forward masthead light. 33 CFR §84.02

---

Minimum Visibility Ranges for Towing Lights

The towing light (yellow, 135° arc) must be visible at the following minimum ranges 33 CFR §83.22:

• Vessel 50 meters or more in length: 3 miles
• Vessel 12 meters or more but less than 50 meters: 2 miles
• Vessel less than 12 meters: 2 miles

---

Why It Matters on the Exam

Exam questions on Rule 24 test several recurring concepts:

1. Two vs. three masthead lights — the 200-meter tow-length threshold is a classic numerical trigger. Candidates must know that the measurement runs from the stern of the towing vessel to the after end of the tow, not just the length of the towline.

2. Towing light vs. sternlight — when towing astern, the vessel shows both a sternlight and a towing light above it. When pushing ahead or towing alongside, the vessel shows two towing lights and no sternlight. Confusing these two arrangements is a common error.

3. Special flashing light on the tow — a pushed or alongside-towed vessel shows a special flashing light at its forward end. This light is yellow, flashes 50–70 times per minute, and has a forward arc of 180°–225°. 33 CFR §83.21 Do not confuse it with the all-round flashing yellow light of an air-cushion vessel or the rapid-flash (120+ per minute) signal.

4. Western Rivers exception — on Western Rivers, the two masthead lights are dropped; only sidelights and two towing lights in a vertical line are required. 33 CFR §83.24 This is a tested distinction.

5. Composite unit — a rigidly connected pushing vessel and pushed vessel show only Rule 23 lights. No towing lights. 33 CFR §83.24

6. Diamond shape — required on both the towing vessel and the tow when tow length exceeds 200 meters. 33 CFR §83.24

---

Common Pitfalls

Pitfall 1: Measuring tow length incorrectly. The 200-meter threshold is measured from the stern of the towing vessel to the after end of the tow — not the length of the towline alone, and not the length of the towed object alone. 33 CFR §83.24

Pitfall 2: Forgetting the diamond on the towing vessel. When tow length exceeds 200 meters, both the towing vessel and the tow display a diamond shape. Candidates often remember only the tow's diamond. 33 CFR §83.24

Pitfall 3: Confusing the towing light color and arc. The towing light is yellow with a 135° arc — the same arc as the sternlight. The special flashing light on the tow is also yellow but has a forward-facing arc of 180°–225° and flashes at 50–70 per minute. These are two distinct lights with different purposes and positions. 33 CFR §83.21

Pitfall 4: Applying Western Rivers rules to all inland waters. The masthead-light omission applies only on the Western Rivers (with the noted exception below the Huey P. Long Bridge). It does not apply to all inland waters. 33 CFR §83.24

Pitfall 5: Treating a rigidly connected composite unit as a towing situation. A composite unit shows Rule 23 lights only — no towing lights, no extra masthead lights. 33 CFR §83.24

Pitfall 6: Forgetting the sternlight on a vessel towed alongside. A vessel towed alongside shows a sternlight in addition to sidelights and a special flashing light at the forward end. A vessel towed astern shows sidelights and a sternlight. 33 CFR §83.24

---

Quick Check

Q1: A vessel is towing astern with a tow length of 250 meters. How many masthead lights does the towing vessel show, and what additional shape is required?

Three masthead lights in a vertical line (because tow length exceeds 200 meters), plus a diamond shape where it can best be seen. The tow also displays a diamond shape. 33 CFR §83.24

Q2: What lights does a vessel being pushed ahead (not part of a composite unit) exhibit?

At the forward end: sidelights and a special flashing light. No sternlight is required on a pushed vessel that is not a composite unit. 33 CFR §83.24

Q3: What is the arc and color of the towing light, and where is it positioned relative to the sternlight?

The towing light is yellow with a 135° arc (same characteristics as the sternlight). It is carried in a vertical line above the sternlight. 33 CFR §83.21 33 CFR §83.24

Q4: A towboat on the Western Rivers is pushing a barge ahead (not a composite unit). What lights does the towboat exhibit?

Sidelights and two towing lights in a vertical line. The two masthead lights required under the standard inland pushing-ahead rule are omitted on Western Rivers. 33 CFR §83.24

Q5: An inconspicuous partly submerged object being towed is 20 meters in breadth. What lights does it show, and what is the minimum visibility range for those lights?

Because its breadth is less than 25 meters, it shows one all-round white light at or near each end, plus a diamond shape at or near the aftermost extremity. Each all-round white light must be visible at a minimum range of 3 miles. 33 CFR §83.24 33 CFR §83.22

Q6: What is the flash rate of the special flashing light on a vessel being pushed ahead, and what is its arc of visibility?

The special flashing light flashes at 50 to 70 flashes per minute and shows an unbroken light over an arc of not less than 180° nor more than 225°, from right ahead to abeam and no more than 22.5° abaft the beam on either side. 33 CFR §83.21

Q7: A pushing vessel and the barge it is pushing are rigidly connected as a composite unit. What lights does the combination exhibit?

The combination is regarded as a power-driven vessel and exhibits only the lights prescribed in Rule 23 — forward masthead light, sidelights, sternlight, and (if 50 meters or more) a second masthead light. No towing lights are shown. 33 CFR §83.24 33 CFR §83.23