Light signals, International

Maneuvering light signals

One flash: altering course to starboard. Two flashes: altering course to port. Three flashes: operating astern propulsion. Five or more short and rapid flashes may back up the danger signal.

Who sounds it

Any vessel may add them to its whistle signals.

How it's sounded

Each flash about 1 second, about 1 second between flashes, and not less than 10 seconds between signals (Rule 34(b)(ii)).

A short blast is about 1 second. A prolonged blast is 4 to 6 seconds. Clips use 1 and 5 seconds.

Worth remembering

Optional. The light, if fitted, is all-round white, visible at least 5 miles.

Study more

See every sound signal, try the free Rules of the Road practice test, or read who gives way, and how Inland differs.

Learn the whole set

Helm drills every signal with flashcards and spaced review, on the web and iPhone.

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Sources

Rule 34(b), Rule 34(d)

Helm is an independent study aid, not affiliated with or endorsed by the U.S. Coast Guard or the National Maritime Center. This page is for study, not navigation guidance or legal advice. Check the current rules before you rely on anything here.