Proper Bridge Opening Signals and Conch Shell Horns

The Conch Shell and the Air Horn

The Conch Shell and the Air Horn

Sometimes boaters have trouble getting a bridge to open for them, there are several reasons why a bridge might not lift as soon as you sound your horn.

The email below is from a Seattle Bridge Operator and was forwarded to me with a request that the boating public be made aware of problems that Bridge Operators have hearing the sound signal requesting the bridge to be opened.

The email speaks for itself.


From:  Fremont Bridge Operator
Sent: Tuesday, April 12, 2016 11:00 PM
To: DOT_Bridge_Operators

Subject: Sub Standard Sound Signals
Hello fellow Bridge Operators,

The other day I heard a vessel on VHF 13 in a belligerent voice say ” __________ BRIDGE ARE YOU GOING TO RESPOND TO MY SIGNAL”?

I knew that Fremont bridge was next so I would see her soon. I watched with the binoculars and listened very carefully.

As the sailboat [Name Redacted] got about 200 feet from the west side of Fremont the vessel operator picked up a Queen Conch shell and blew into it and I heard absolutely NOTHING. The door was open and A/C on low. I responded with a horn signal and opened the bridge. I recommended a large air horn via intercom and received smiles and waves.

I am sure you have all seen the Conch shells, Triton Trumpets, duck calls, Oscar Meyer Weiner whistles and whatever that are very impressive to the crew but don’t do much for us.

The season is just starting and if we are proactive early maybe we can avoid some erroneous boater complaints.

This is the direct quote from CFR 33, 117.15 that we need to get out to as many boaters as possible:

(b) Sound signals. (1) Sound signals shall be made by whistle, horn, megaphone, hailer, or other device capable of producing the described signals loud enough to be heard by the drawtender.

Those of you who network with boaters via boat shows, sailing regattas, boat clubs, USCG Auxiliary, maritime blogs or other social events please get the word out. Not as a Bridge Operator but as an ordinary civilian unless your communication has been approved by the cities media protocols and Greg or Mary.

Fremont Bridge Operator
City of Seattle Department of Transportation


In the above case, despite Conch Shell Horns having been in in use for hundreds of years, this time it was not quite up to the job.

Sound producing devices come in many versions, the one I see in use the most is the hand held air horn.  (note; in cold weather wear gloves when operating, the canister can get quite cold to hold). Shaking the canister will give you a bit of an idea how much propellant is left.  Having a spare horn and canister is also prudent, the horn always seems to run out of propellant when the horn is needed the most.

Hand held horns also come in a pump it up version where you charge the air horn with a hand air pump.  Make sure you check the canister for proper pressure and top it off as needed.

Human operated horns are also available, you blow vigorously into one end and a diaphragm is vibrated, they are quite loud but some seem to sound like a love sick Moose.  But they never have an empty canister.  Remember a Prolonged Blast is 4 to 6 seconds and that is a lot of air and a very long exhale and most people seem to trail off at the end.

Even if you have a fixed electric  horn on your boat, carrying a hand held horn with a pressurized canister is a good idea in case the electric horn stops working.  Some people have pointed out that keeping an electric horn working and loud takes extra maintenance, and checking the electric horn for proper operation each trip seems to annoy the neighbors.

Some points to remember, even with a proper sound producing device many factors can work to reduce the ability of a Bridge Operator or other vessel to hear a proper sound signal.  Some of the factors can be, distance from the bridge, adverse wind and weather such as rain reducing the distance the sound will carry and the doors and windows in the Bridge Operators control tower being closed due to weather.

Road noise is another factor that boaters may not be aware of.  It is very loud
in the Ballard tower and the noise is directly between the Bridge Operator and
the eastbound vessels.

A few points to consider, having a sound producing device a bit louder is better than quiet, a spare device in case the one you are using suddenly runs out of pressure (for the common hand held horns, or a spare canister).  If you are using a hand held horn, keep it readily available, I have needed to use my air horn several times to warn other vessels that we were stand on and  they were on a collision course with us and they did not seem to be aware of our vessel, having the horn close to the helm where the driver or crew member can quickly grab it is good.  My horn is right inside the companionway and an easy reach for the crew.

The proper sound signal for all the bridges from Shilshole Bay to Webster Point (including the Ship Canal) is one Prolonged (long) one Short.  For more information on the bridges operated by the Seattle Department of Transportation please see their web site.

For general information about special regulations in the Seattle area, including Lake Washington and Lake Union, please see: Avoiding the Seattle Harbor Patrol’s Attention

Bridges can also be contacted on VHF channel 13 if needed.

The CFR (Code of Federal Regulations) does allow bridges to wait to open, this is commonly done to help clear vehicle traffic off the bridge or to group boats together so one opening can be used for many boats.  Also a bridge can be held down for emergency vehicles such as Fire and other emergency vehicles.  Bridges also do not need to life during rush hour traffic and special events, see the link above to the Seattle Department of Transportation for specific information on closed periods (generally Monday through Friday 7am to 9am and 4pm to 6pm except some holidays).

Some fine print on Sound Signals.  Vessels under 39.4 ft (12 meters) are not required to carry a horn, but they must carry a device capable of making an “efficient sound signal” The human voice (yelling) is specifically excluded as meeting the requirements of a sound producing device.   A vessel 12 meters to 20 meters in length must carry a horn that produces a sound audible for 1/2 mile.

Or you can also ask a passing powerboat to sound their horn for you if your horn is out of air.  Using the universal signal of pulling your fist down like you are pulling on a Steam Locomotive Horn has also been used successfully by some friends.

And if all else fails, get out the old antique horn and huff and puff.

Antique Boat horn - in case all else fails - yes it does work and it is loud!! Photo by Lee Youngblood

Antique Boat horn – in case all else fails – yes it does work and it is loud!!
Photo by Lee Youngblood

A special thanks to Kahuna Dave and the folks at The Alki Surf Shop in West Seattle for letting me take pictures of their Conch Shell Horn.  They also said that Conch Shell Horns were quite loud when blown properly, sadly Kahuna Dave was not in the shop to demonstrate their horn for me the day I visited.

Thanks Lee Youngblood, long time friend, sailor and Yacht Broker for the picture of the antique horn.

Thanks also to Pam C-K the U.S. Coast Guard Auxiliary District 13 Staff Officer for Navigation Systems for sending the email on to me and providing feedback and suggestions for the article and the Seattle Bridge Operators for also helping with suggestions and feedback “from the tower” so to speak.

Thanks for your interest in and support of boating safety

 – c / m –

This entry was posted in Boating Safety, Sailing and Boating Skills and tagged , . Bookmark the permalink.

7 Responses to Proper Bridge Opening Signals and Conch Shell Horns

  1. Saffy The Pook says:

    Which begs the question…Why don’t they use the VHF as the primary signaling means?

    • captnmike says:

      Interesting question and so far my research and checking with people has not turned up a “prolonged horn” memo so far.

      Here are my thoughts based on conversations with others.

      Looking at the CFR’s (Code of Federal Regulations) for Bridges indicates 4 types of signals, Sound, Flags, Lights and Radiotelephone.

      There are five bridges and the locks located close to each other, using sound signals keeps the traffic on VHF Ch-13 down on busy days. Commercial vessels almost always use the VHF as they have maneuvering and safety issues because of their size so they call way ahead to schedule an opening.

      As a recreational vessel you can us Ch-13 if you want – nothing illegal about calling a bridge
      The Seattle Harbor Patrol’s Booklet on Seattle Regulations indicates that Sound is preferred. ( )

      The bridges predate the common use of VHF radios by recreational vessels – so perhaps part tradition – Seattle has many marine traditions, some large like opening day and Duck Dodge to name just two.

      Not all recreational vessels have VHF radios even today.

      The Ballard and Freemont Brides can be heard on the VHF at the Spokane Street Bridge, so the bridge traffic would add traffic in general.

      In Florida sound signals are not used much, in many areas there is a significant tidal current up to around 5 knots. With that amount of current to deal with boats requiring a bridge opening will call ahead so they don’t need to station keep in the current or turn broadside to the current in what is sometimes a narrow channel. So using the radio to schedule an opening is a safety issue.

      The Seattle DOT web site states ( )

      Pleasure vessels are requested by the Coast Guard to use a whistle signal from 7:00 AM to dusk.

      But it is not in the CFR so it could be a Local Custom, perhaps related to radio traffic.

      Sorry no paragraph in the CFR. Hope this helps a bit. Also my thanks to those that helped with background information

      My suggestion is to use what works best for you and be polite to the Bridge Operators and keep in mind that the traffic noise and weather problems might cause you to need to use a second sound signal. Remember also that there are several marinas close to the bridges so a signal is needed to help the Bridge Operator understand your requirements.


  2. andy says:

    The bridges regulations governing operations set forth a delay of up to 10 minutes to clear traffic (from SDOT website). Shouldn’t be any wait longer than that so long as you sounded an appropriately loud horn. It helps when the bridge tender responds so that a vessel knows that they have been heard, even if it is 5 short blasts to signal a delay. There is a form to report delay of opening at a drawbridge, (not posting the link, serious business to report it to Coast Guard, you’ll go find it if it’s that serious)

    Sound signals are very efficient for most openings. They minimize the amount of radio chatter.

    • captnmike says:

      The Seattle DOT is working on standardizing the response time at all bridges to match the CFR – even if the response is the 5 short that you will need to wait a bit – the not knowing if the sound was heard is annoying to say the least – If I know the bridge heard the signal then I can decide how I am going to station keep until the bridge can open

      Thanks for dropping by

  3. Pingback: The View From The Fremont Bridge Tower – The Bridge Operators Perspective | Boating Safety Tips, Tricks & Thoughts from Captnmike

  4. Dave says:

    If you give a sound signal to a bridge requesting an opening and you don’t hear anything back within 30 seconds, the Bridge Operator did not hear your sound signal. Repeat, closer and louder.

    • captnmike says:

      I usually give a bit more time than the 30 seconds on the theory the Bridge Operator might be doing something but then the second signal is a bit extra long and closer – sort of a Waaaaake Up if one wants to think of it in those terms

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