• A short blast of the whistle should have a duration of about one second. A prolonged blast of the whistle should have a duration of four to six seconds.
• One short blast to mean "I am altering my course to starboard".
• Two short blasts to mean "I am altering my course to port".
• Three short blasts to mean "my engines are operating astern propulsion".
• A power driven vessel making way through the water except when fishing, under sail, towing or being towed, shall in restricted visibility sound one prolonged blast at intervals of not more than 2 minutes.
• A vessel at anchor in restricted visibility shall ring the bell rapidly for about five seconds at intervals of not more than one minute.
• A vessel not under command, a vessel restricted in her ability to maneuver, a sailing vessel, a vessel constrained by her draft, a vessel fishing, a vessel engaged in towing or pushing shall sound at intervals of not more than 2 minutes, one prolonged blasts followed by two short blasts.
• Sound 5 short rapid blasts if you fail to understand the intentions of the other vessel.

  For a complete set of International and Inland Rules of the Road, please get Coast Guard Navigation Rules COMDTINST M 16672.2A available from:

Government Book Store
Federal Building
915 Second Avenue
Seattle, WA 98174

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