Incident Investigation: Rethinking the Chain of Events Analogy

Article on EHS Today By Allan Goldberg on 17 November 2003. It disputes the often used notion that incidents occur due to a 'chain of events' suggesting the logic behind the chain may be its weakest link.

The safety profession often refers to a chain of events and then looks for the weak link as a means of identifying what went wrong that allowed the incident to occur. We then very often go further and identify a specific human error that was made, and the person who made it. That person, and/or what they did or didn't do, is thought of as a weak link in the sense of a "performance" chain. Rigid adherence to this way of thinking can lead to some significant errors in improving safety performance. We can and should avoid them.

There are three main problems that this traditional thinking about the chain of events analogy can lead to:

1. Incidents are not linear sequences and instead multivariable meaning there are many different possible paths to an incident.

2. The "weakest link" approach implies that there is only one "main" cause for a given incident whereas most incidents have multiple causes

3. Looking for the weak link creates a focus on the point of failure which is usually well removed from the best point of control. This leads t overemphasis on behavioral approaches and misses the true root causes.

Every link in a physical chain is in fact only connected to one other on each end. The real world chain of events, however, has many more "options" in terms of inputs and outputs. Breaking a single "link" will not necessarily preclude the end event from occurring.

Human actions are a combination of attitudes, beliefs, moods, training, awareness and many other factors. The point being, we may not respond to a given situation today the same way we did yesterday. The key idea here is that many sets of inputs and outputs are possibilities in incident causation. We must be very careful to avoid thinking about causation in a purely linear manner.

Root causes are likely to apply to a whole series of potential incidents, not just one event. These root causes are in fact the key to prevention of future incidents. And contrary to what all too many people may think, human error is not one of them! Human error itself is a symptom that there are other problems in the management of the work that is taking place. These error problems themselves have root causes. When a worker makes an error or fails to follow a procedure, there are reasons that set up the situation. These are the root causes that must be found.

Avoiding Pitfalls

1. Recognize the multivariable nature of incident causation.

2. Understand the Principle of Multiple Causes.

3. Realize the point of failure and the point of control are not necessarily the same. Seek to understand the problem as part of the overall system, and identify where the system itself can be best controlled.

Andy Brazier

Human error 'doing more harm than enemy'

Western Morning News on 26 January 2009

Air Chief Marshal Sir Jock Stirrup, the Chief of the Defence Staff (CDS), reported as saying accidents and mistakes in combat zones do more to undermine British troops' fighting abilities than attacks by the enemy, according to the head of the armed forces.

Sir Jock said that more than half of "accidents and incidents" which have led to troops being killed or injured on operations were down to human error.

The CDS also admitted that troops who make mistakes were too afraid to own up to their failings because of concerns they would be unfairly punished.

In an article for a Ministry of Defence publication, Sir Jock said that the absence of a "just culture" in the forces meant the military had failed to learn valuable lessons from its mistakes.

Since March 2003, 320 troops have died on operations and several thousand have been injured. And while the vast majority have been killed by enemy action, the CDS said that errors made by British troops had played a significant part.

In an article for "Desider", a magazine for the defence, equipment and support arms of the military, Sir Jock wrote: "Evidence shows that more than half our accidents and incidents are down to human factors. In other words, it is our people who are causing the most damage to our fighting capability. We must do something to drive down the number of accidents and incidents.

"One of the most effective ways of doing this is to promote a culture that encourages open and honest reporting that allows for a structured investigation of errors.

"This action should address all individual, systemic and environmental issues relating to an incident and allow us to learn from what took place.

"The actions and feedback will prevent us making the same mistakes again. It is the justness of what we do that gives rise to a just culture."

The CDS added: "To me, such a culture is based on trust. It suggests a working environment where individuals are encouraged to contribute to providing essential safety information and where they are commended for owning up to mistakes."

Sir Jock then asked: "Do we have a just culture in place? Is there a tolerant and non-punitive environment where mistakes can be admitted freely before they can cause an accident?

"My sense is that it is not as well established as it might be, nor as comprehensive as I would wish. The greatest challenge for senior leaders and those with command responsibility, including me, is to make a just culture a fact, not just an aspiration."

Sir Jock's comments come soon after the publication of a document in which General Sir Richard Dannatt, the Chief of the General Staff, revealed that 10 out of the 89 soldiers killed in combat in 2007 were "entirely avoidable accidents".

New Study Shows Patient Safety Benefits of Ensuring Rest for Doctors

Article by Jennifer Anderson 2 February 2009 on ergoweb.com website.

The University Hospitals Coventry and Warwickshire NHS Trust conducted the new study, which was reported by the BBC.

Nineteen junior doctors working on the endocrinology and respiratory wards at the hospital participated in the 12-week study. Nine were put on a 48-hour per week pattern that met the conditions of the European Working Time Directive (EWTD) and 10 were on a traditional pattern, where they worked up to 56 hours.


Two senior doctors, who were unfamiliar with the shift patterns of both groups, reviewed their errors by checking case notes.

Doctors working to the EWTD pattern made 33 percent fewer errors than their colleagues on the traditional pattern, and there were fewer potentially life-threatening events.

Andy Brazier

'Human error' kills Google seach

Article by David Walker 2 February 2009 at T3 gadget website

Apparently someone at Google inputted the symbol '/', which contrived to label all sites as unsafe for a portion of Saturday afternoon (UK time). This left all sites in the Google universe classed as unsafe, with the warning 'This site may harm your computer' appearing under the website name. Even if you went to Google, Google Maps, Gmail or indeed any other Google site.

Initially, Google blamed the non-profit website StopBadware.org, but later changed tact and offered up a new statement taking full responsibility.

Andy Brazier