Weak Signals : What are they and why do we care?

“Weak signals are subtle signs or indicators which may indicate that some of the barriers intended to prevent an incident are failing or missing. Weak signals can be observed in equipment, human factors and near misses.”


High Reliability Organizations (HRO) are commonly considered to include nuclear power systems, naval vessels such as aircraft carriers and healthcare, amongst others.  They are characterized by five principles:

    1. Preoccupation with Failure
    2. Reluctance to Simplify Interpretations
    3. Sensitivity to Operations (an HRO Distinguishing Characteristic)
    4. Commitment to Resilience
    5. Deference to Expertise

As part of an HRO’s preoccupation with failure, they are on the lookout for potential signs of failure and actively seek out “weak signals.” While these weak signals might not point directly at a potential failure, when aggregated, they may indicate a weakness in the system that left unchecked will lead to failure.  A significant difference between an HRO and companies with a less-evolved safety culture is that these weak signals are not considered distractions, even though the majority may turn out to be nothing.

The graphic below from Skybrary highlights some characteristics of weak signals.  Weak signals are by definition, not as easily perceived as strong signals and, as a result, can be rationalized away or discounted.  One example of this from the business world was the introduction of the iPhone.  This was discounted early on by Microsoft executives as too expensive or inconvenient.

In the maritime industry, from a shipboard safety standpoint, we aren’t looking for market trends, so our weak signals will differ from those of business.  From a technical viewpoint, some of the weak signals on a vessel might be a piece of machinery that is running differently, a strange vibration or maintenance that is required at an abnormal interval.  From a human standpoint, we might focus on near misses and safety observations to identify some of the human factors at play.



Seably was founded together with The Swedish Shipping Association in 2017, out of strong demand from the shipping cluster for better ways for seafarers to conduct their mandatory training.  They offer a free short course “Reflective Learning – Weak Signals.”  This 30-45 minute course provides a good introduction to weak signals and, in particular, weak signals in the maritime industry.

Dr. Jake Mazulewicz discusses practical applications of HRO principles in a recent article on LinkedIn.  In How to Build Resilience Instead of Chasing Zero Errors, Three strategies that can be implemented in any organization seeking greater resiliency are:

  1. Watch for Weak Signals
  2. Embed Fail Safes
  3. Practice Uncertainty

Resilience Engineering and the HRO Principles both include this focus on weak signals.  Now, in the maritime industry, we might not outwardly state that individual shipping companies or ships are High Reliability Organizations, when seen through the lens of maritime accidents our opinions might change.  When the complexity of the maritime industry and the ripple effect of one incident, such as the grounding of MV Ever Given in the Suez Canal, on the world economy is considered, perhaps we want to adopt some of these principles.

Weak signals are a good place to start.  But reporting of weak signals will be for nought if it is not paired with a proactive safety culture.

Check out Seably’s training.  Pass it along to your organization.  Think about how you might use the concept to better safety both aboard and ashore.

And, in the meantime, let’s be safe out there.

Additional Reading and Links

Reflective Learning – Weak Signals – Seably
How to Build Resilience Instead of Chasing Zero Errors – Jake Mazulewicz, Ph.D.

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