What lights does a vessel towing show?
Two masthead lights in a vertical line (three if the tow is over 200 m), plus sidelights, sternlight and a yellow towing light above the sternlight.
The tow's length is measured from the tug's stern to the end of the tow. Over 200 m, both tug and tow show a black diamond by day. The vessel being towed shows sidelights and a sternlight but no masthead light.
- 50 m and over: she also shows her normal aft masthead light.
- Pushing ahead or towing alongside: two masthead lights, sidelights, sternlight, no towing light.
- If the tow stops her turning away, she adds red-white-red (or ball-diamond-ball).
- In fog the tug sounds one prolonged and two short; a manned tow follows with one prolonged and three short.
Source: COLREGS Rule 24, Rule 27(c) and Rule 35(c), (e).
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