Maritime Safety at Different Scales

When this thread was posted, Maritime Safety Ideas I wondered what kind of ideas? Thought again of the apparent paradox of the Deepwater Horizon. The DWH won a safety award and tragically suffered an explosion that killed 11 crewmembers on the same day.

In meteorology weather is analyzed at different scales, synoptic, mesoscale, and microscale, there is macroeconomics and micro and so forth.

In maritime operations safety could be at the scale of the regulators and company, vessel or at the scale of “on deck”. Safety at deck scale could be proper wearing of PPE, following relatively simple procedures, micromanagement. Moving from the deck to vessel and company scale things start to get more abstract and complex.

A comprehensive safety management system has to span all scales.

its easy to win an award, you just never report any incident.

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Monitoring PPE compliance on deck , for example is simple and low cost.
Low-risk / high-consequence decisions with potentially high costs are more difficult.

sure but thats why there is reporting.
In the DWH case they dodged lots of issues but finally the swiss cheese lined up, no surprise

Anatomy of an Error


The idea of different scales is more in line with Nancy Leveson’s work than the Swiss Cheese model.

This picture is just humbug.

With all slices identical and with the same orientation it protects nothing, all four holes are open; the probability of passage is 100%. The same error is just repeated.

With different slices, the probability of passage is low; every supplementary and different slice diminishes this already low probability…

Doesnt matter the size or the shape of the holes, just that they line up, usually one by one, thats why people get caught out.

I know the Swiss cheese metaphor was more about the error chain, but it makes a great metaphor for scales too. Regulatory loopholes - company culture issues- SMS holes - gaps in onboard implementation. I hadn’t given much though to scales previously.

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My pic is more convincing :wink:


Thinking in terms of scale may or may not be useful, It was something that occurred to me thinking about mooring operations. Crew members on deck are warned to pay attention, avoid standing in the bight and so forth but the decision to use one or two tugs for example also can effect safety down on deck.

Nancy Leveson uses levels within a hierarchy, levels higher up in the hierarchy would be system level which would be system scale.

Leveson’s book is available on line: Engineering a Safer World.

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