33 CFR § 83.24 - Towing and pushing (Rule 24).
(a) A power-driven vessel when towing astern shall exhibit:
(i) Instead of the light prescribed either in Rule 23(a)(i) or 23(a)(ii) (§§ 83.23(a)(i) and (ii)), two masthead lights in a vertical line. 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;
(iii) A sternlight;
(v) When the length of the tow exceeds 200 meters, a diamond shape where it can best be seen.
(b) 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 (§ 83.23).
(c) A power-driven vessel when pushing ahead or towing alongside, except as required by paragraphs (b) and (i) of this Rule, shall exhibit:
(ii) Sidelights; and
(iii) Two towing lights in a vertical line.
(e) A vessel or object other than those referred to in paragraph (g) of this Rule being towed shall exhibit:
(ii) A sternlight; and
(iii) When the length of the tow exceeds 200 meters, a diamond shape where it can best be seen.
(iii) 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 of the towing vessel, and a single set of sidelights as far forward and as far outboard as is practicable, and a single special flashing light.
(i) If it is less than 25 meters in breadth, one all-round white light at or near each end;
(ii) If it is 25 meters or more in breadth, four all-round white lights to mark its length and breadth;
(iii) If it exceeds 100 meters in length, additional all-round white lights between the lights prescribed in paragraphs (g)(i) and (ii) of this Rule so that the distance between the lights shall not exceed 100 meters: provided, that any vessels or objects being towed alongside each other shall be lighted as one vessel or object;
(iv) A diamond shape at or near the aftermost extremity of the last vessel or object being towed; and
(h) Where from any sufficient cause it is impracticable for a vessel or object being towed to exhibit the lights or shapes prescribed in paragraph (e) or (g) of this Rule, all possible measures shall be taken to light the vessel or object towed or at least to indicate the presence of such vessel or object.
(i) Where from any sufficient cause it is impracticable for a vessel not normally engaged in towing operations to display the lights prescribed by paragraph (a), (c), or (j) of this Rule, such vessel shall not be required to exhibit those lights when engaged in towing another vessel in distress or otherwise in need of assistance. All possible measures shall be taken to indicate the nature of the relationship between the towing vessel and the vessel being assisted. The searchlight authorized by Rule 36 (§ 83.36) may be used to illuminate the tow.
(j) Notwithstanding paragraph (c) of this Rule, on the Western Rivers (except below the Huey P. Long Bridge at mile 106.1 Above Head of Passes on the Mississippi River) and on waters specified by the Secretary, a power-driven vessel when pushing ahead or towing alongside, except as paragraph (b) of this Rule applies, shall exhibit:
(i) Sidelights; and
(ii) Two towing lights in a vertical line.
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