What about fog signals? Are they still serving a purpose?


30 year old Tideland Signal fog signal under the main deck, still working. What a great investment!

Audible fog signals have been around for centuries, warning seafarers for hazards ahead in foggy conditions. Initially ringing a bell, or firing a canon, later developed into the electronically powered fog signals we see today, such as the Tideland Signal fog signals.

Fog signals were used both onshore and offshore, on vessels and platforms, but these days you will struggle to still find them onshore. Next to the lovely Kinnaird Head Lighthouse, in Fraserburgh, Scotland, you actually will see them, even though they are not operational anymore. As a result of the fast developments in navigational aids over the last decades, such as radar and – more recently – AIS, they are not needed anymore. The developments in navigational aids have a nice side-effect: improvement of quality of sleep of the people living next door.

Yup, this will keep you awake at night – Fraserburgh, Scotland

On offshore structures, whether it be a platform, a jacket or a wind farm, you still will find fog signals. Mainly for two reasons:

The first being that fog signals tend to have a very, very long life span. Secondly, they are still mandatory in many countries.

There are a lot of old platforms in the North Sea. In the Dutch sector, the majority of the platforms are over 25 years old, and typically still use the exact same fog signals they installed when commissioning the platforms. The reality is, that all good things come to an end, so even the fog signals that have been in service for sometimes over 3 decades, tend to start showing problems. Given the current market conditions, even the largest oil majors need to watch where and how they spend their money, so the question arrises whether or not to retire the old fog signal and replace it by a new one, or not replacing it at all and continue operating the platform without a working one.

But the same question also pops up with platform abandonment, or when new structures are installed at sea (in the oil and gas industry this is very rare at the moment, I admit).

Needless to say, this is rather a hot topic at the moment for operators of platforms that need to make a decision whether or not to buy a new fog signal.

In essence it comes down to the question: “Do we really need a fog signal?”. And the answer is very simple, when in UK or Dutch waters: “Yes, you do, because it is mandatory according to the regulations.” The Norwegians have a different approach, the fog signal is no requirement in their part of the North Sea anymore. Denmark is in doubt, officially it is required, but for abandonment, it is actually allowed not to install one.

Although the answer to the question is very simple and straightforward, the question itself is actually very legit. But the question should be asked slightly different: “Do fog signals, given the technical developments, actually still serve a purpose?”. And if the answer to that question is a (partially) “no”, why would you spend money on it?


Tideland Signal AB-560  safe area, 2 nm fog signal


Fact is, that the regulations are written decades ago, and do not take into account new technologies. Even the IALA O-139 “The Marking of Man-made Offshore Structures”, which is a recommendation, not a regulation, does not even mention AIS as an aids to navigation in the section about marking offshore structures in general, under which oil and gas platforms fall. Its predecessor, the O-114 publised in 1998, has been the basis for the local regulations, such as the Dutch Mijnbouwregeling from 2002. 16 years later, the Mijnbouwregeling has not been updated, hence focussing primarily on visual and audible aids to navigation and basically neglecting more advanced tools.

Strangely enough, onshore there is a tendency to decrease the range of navigational aids: shore based fog signals are long gone and replacement lights for light houses will have less intensity, and thus a smaller ranger, than previously. In Belgium, for example, a typical light house would have a range of 25 nautical miles (nm) or more, but when their light is replaced these days, their range will drop to about 18 nm. The main reason: improved navigational equipment onboard vessels reduces the need for long-range lanterns. And – as a side-effect –  reduce power consumption dramatically, quite an important issue these days.

And of course, this is true. Any vessel sailing the North Sea is required to be able to receive AIS messages. Any vessel sailing the North Sea is required to have radar. We have better night vision than owls, regardless whether it is foggy or not.

And even though collisions between vessels and platforms are considered to be the largest risk in the Dutch part of the North Sea by the governing body, Staatstoezicht op de Mijnen, and even though marine traffic obviously has increased dramatically over the last decades, and even though there are more than 600 platforms and several wind farms in the North Sea, we are more capable of spotting offshore structures than ever before. To put it quite simple, visiting Marinetraffic.com allows me to see offshore structures in the Gulf of Mexico, whilst sitting at my kitchen table at home in the Netherlands.

Collisions are most certainly a threat, and the only reason why we use aids to navigation in the first place. Not only has traffic become more dense, the average vessel size has increased significantly as well. Vessels with a Loa of over 350 meters are a common sight. This means that we are looking at a displacement of close to 200,000 tonnes. Vessels of this size require quite a distance to come to a full stop and the radius of a turn of these giants is given in miles, not in meters. When a vessel of this size and displacement would hit an operational production platform, the consequences are obviously severe. So proper marking of any offshore structure is not just a “nice to have”, it is critical for safety at sea.

But picture this: according to the requirements, fog signals should have a range of 2 nm (1/2 nm for the backup fog signal in the UK). What are the odds that you will hear a fog signal when you are standing in a well insulated bridge of a modern ultra large vessel, with the bridge located at around 3/4 of the ship’s length?

Maybe, a vessel like this:

Large vessel indeed

The answer is rather clear, I would say: the odds are very, very slim. In fact, when you are on the bridge of one of these large vessels, it is not unlikely that by the time you actually hear the fog signal, most of the offshore structure is already gone because of the impact of collission.

The days that people on the bow, on the outside of the bridge or in the crow’s nest, are on the watch to hear fog signals warning them for danger, are gone. These days we stay warm and cosy, with a cup of Nespresso, inside the bridge and watch the screens for upcoming mayham.

I was doing a site acceptance test of an Aids to Navigation skid onboard a modern vessel last year. Maybe I should mention the name of the vessel? The Pioneering Spirit of Allseas, the largest vessel in the world.

The fog signal, mounted on the skid, was approximately 150 meters from the bridge, as the crow flies, but when testing the fog signal, it could not be heard on the bridge. Well, actually it could be heard, but only because we were on permanent comms with the bridge and the sound of the fog signal was transmitted through the portable radios. Important to note: it was a perfect day, no wind at all.


Onboard the Pioneering Spirit, with the skid with fog signal on top of the test platform (top left corner of the platform)

Over the course of last year, I have commissioned Aids to Navigation systems on several abandoned platforms, all including fog signals. Most of these platforms were small satellites, with a length of just over 30 meters. In all cases, the fog signals were installed on the main deck, whereas the power supply was installed on the helideck. During testing of the system, another logical shortcoming of sound became apparent: during strong winds, it was hardly possible to hear the fog signal at all, even though I was less than 40 meters away from the source.


Fog signal on the main deck of an abandoned platform

Sounds can blow you away, but the opposite is also true: sound itself can be blown away. Or blocked, by the structure of the topside, for example.

Dutch regulations state that each offshore structure should be fitted with a fog signal, with a range of 2 nm. It does not, however, require that the fog signal should be heard from all directions, so if you use a single fog signal on the corner of a very large platform, you still comply to the rules. Even though you are certain that the fog signal during most of the time will not be heard when standing on the opposite corner.

So, what’s my point of view?

For structures outside the 12 nm zone, a fog signal basically serves no use anymore. There are much better ways to mark these structures, the odds that the fog signal cannot even be heard on the bridge of passing vessel is high, and these same ships will have noticed the structures way in advance by using radar, AIS or electronic charts. Or, how oldskool, noticed the 10 or 15 nm marine lanterns.


Oldskool? State of the art LED lantern actually.

For structures within the 12 nm zone, it actually makes sense to use fog signals, since there are much more small vessels and boats sailing these waters, many of them for leasure, with less experienced crew. And often less advanced electronic equipment. In particular for near shore windfarms, fog signals still serve a useful purpose.

One final thought:

On operational platforms, power consumption is not an issue. However, on abandoned platforms, where the power needs to be supplied by the combination of batteries and PV modules, it is. In an AtoN system, the fog signal typically is the largest user and avoiding having to use them, will actually make AtoN systems much cheaper, while not reducing safety. Just make a physical AIS transmitter mandatory.

So, I think it is time to partially retire the fog signal. It is no longer needed in the area where predominately professionals are at work. But let it enjoy its retirement in the areas where it still can support marine traffic and can help to avoid accidents, being close to shore.

As I mentioned before, all good things come to and end. So long good friend, you have served your time well.


Disclaimer: a fog signal is an expensive piece of kit and from a commercial point of view, manufacturers will not necessarily agree with me. But hey, this is my personal blog 😉


About robinjansen

MD of PC Jansen Marine Agencies BV, agents for several international manufacturers of equipment to the offshore and marine industry.
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1 Response to What about fog signals? Are they still serving a purpose?

  1. bob macgregor says:

    Couldn’t agree more. Any vessel large enough to do damage in a collision carries navigational aids sufficient to avoid collision. Any vessel so small that doesn’t carry aids should not be proceeding at speed in fog and thus will not cause damage to structure or itself. On top of that, one cannot navigate in fog by the sound of a fog horn or electronically generated signal. It is omnidirectional and the different densities of water vapor in fog cause the sound to echo and bounce around. Perhaps at sea on a derrick there could be a reason for a fog horn if there is a high volume of small vessel traffic but land based fog horns are simply an anachronistic expensive nuisance. With the availability of cheap navigational aids today the responsibility to navigate safely should be on the shoulders of the vessel operator.

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