Human Factors, Human Error & The Role of Bad Luck in Incident Investigations


As an Organisational Psychologist working with clients in various safety critical industries over the past 25 years I often get asked for some advice on how to better manage the 'human factor' within an organisation. Usually the conversation begins with a frustrated question from a senior manager that goes something like this. "We have all these mature systems and procedures in place and a low Total Recordable Injury Frequency Rate (TRIFR) but it is the 'idiot factor' that we can't seem to stop. How do we stop people doing stupid things". Of course herein lies part of the problem - using the terms 'stupid' or 'idiot' will do little to help.

This article will outline how we can improve the quality of workplace health and safety investigations by better understanding the role of human factors. A better understanding will ultimately provide insight into practical error management strategies designed to tolerate the errors that individuals will ultimately make.

Human Error is an action or inaction

To better understand the human factors contribution to workplace incidents and accidents, we first need to determine what the outcome of poor human factors is; and that is human error. Often the terms human error and human factors are used interchangeable - but they are quite different things.

Human error is a generic term that involves all those instances where a planned activity fails to achieve its intended outcome. For example, forgetting to set your park brake in your car or misapplying your vehicle brakes in wet and slippery road conditions.

The best non academic definition of human error comes from my former PhD supervisor Professor James Reason who often remarked that saying that an individual makes errors are about as useful as breathing oxygen or implying it was bad luck. In other words errors are quite normal. To make this point I ask the participants in my training courses if they remember the movie Meet Joe Black. You know the movie with Brad Pitt who plays the part of the devil who has come to take the life of the business mogul played by Anthony Hopkins? There is a scene in the movie where Pitts character reminds people that there are two certain things in life - death and taxes. What Mr Pitt forgot was the third most certain thing in life - human error. So human error does not really involve idiots then unless we all admit to being idiots!

So just how normal is human error? In fact, research suggests that regardless of the activity or task being conducted, humans make between 3-6 errors per hour. One study in aviation maintenance conducted by my former Australian Transport Safety Bureau (ATSB) colleague Dr Alan Hobbs, found that aviation maintenance engineers made on average 50 observable errors per work shift. The good news is that most of the time, these errors are self-corrected and they have little consequence.

The following represents a summary of agreed views about human error from experts on the subject:

  • Errors do not usually occur randomly - there are generally reasons for them.

  • An active hazard must be present for errors to become consequential - not paying attention when working at height is more of a problem that not paying attention when watching a movie.

  • Even a relatively small error can trigger a very serious accident, if the system is vulnerable and has poor defences or risk controls.

  • Human error knows no boundaries. Regardless of experience level, professionalism, gender or national culture - everybody makes errors. However, the silver lining is that experts at particular tasks are often better than novices at anticipating errors, and taking action to prevent them becoming serious.

Saying that an individual made an error is about as useful as saying it was an Act of God. Human error needs to be explained and one way to start is to understand that human errors are not all the same; they can be divided into either unintentional or intentional actions.

  • Unintentional actions—those in which the right intention or plan is incorrectly carried out, or where there is a failure to carry out an action. These actions typically occur due to attention or memory failures.

  • Intentional actions—those actions that involve conscious choices. These actions are largely due to poor judgment or motivational processes.

The diagram below illustrates the difference between unintentional and intentional actions which is covered in the Incident Cause Analysis Method (ICAM) training session on human error.

Types of Human Error

Poor Human Factors can lead to Human Error

So if human error is what an individual or team commits ‘actively’ (someone did or didn’t do something); then human factors are the reasons why the errors occur!

Human factors is an umbrella term for the study of people’s performance in a specific environment. Within the workplace, human factors is about the relationship between people and the equipment they operate, their environment, the information and knowledge available to them, and importantly, their interactions with other people.

Simply put human factors can be thought of as conditions that if not managed correctly can lead to human error. For example, a condition like fatigue can lead to poor decision making (mistake).

Within the ICAM Investigation model, specific Task/Environment Conditions are provided that can lead to human error. For example, workplace factors such as those outlined below (poor lighting, housekeeping or visibility) can cause distractions, promote violations or result in poor decisions.

Task/Environment Conditions: Workplace Factors

Also specific human factors issues (fatigue, personal issues or change of routine) including those outlined below can greatly increase the probability of human errors occurring.

Task/Environment Conditions: Human Factors

The best way to illustrate the relationship between human factors and human error is via the use of a case study.

Case Study

The following case study is based on actual events; however names, locations and other identifying details have been changed.

On 19th March 2015 at approximately 15:40 Western Standard Time (WST) three passengers, departed their accommodation facility in a 200 Series Landcruiser wagon, bound for the West Australian town of Geraldton some 400km to the South West. At 17:30 WST and only 115km from their departure point on the unsealed Carnarvon-Mullewa Road, while travelling at approximately 100km/h, the front right wheel impacted a standing pool of water, resulting in the steering wheel sharply pulling to the right. The driver overcorrected with left input causing the vehicle to travel sideways, and control of the vehicle was lost as it ran off the left of the road colliding with several shrubs and small trees. None of the occupants of the vehicle sustained any injuries.

The impact with several shrubs and trees on the side of the road, resulted in a punctured front passenger side tyre as well as minor vehicle panel damage including a smashed indicator, and damage to the plastic liner of the wheel arch.

The vehicle was able to be driven back on to the road where the punctured tyre was replaced. The vehicle was then driven safely to Geraldton, by one of the passengers, without further incident.

The incident was reported by the original driver to the site manager via phone once back in mobile range.

Picture 1: Puncture damage to front passenger tyre.

Picture 2: Road conditions at the time of the incident.

While it was determined that the Actual Consequence of the incident was “Minor” with less than $2,500 damage to the Landcruiser, the Potential Consequence was determined to be “High” with the potential for fatal injuries to be sustained by the three occupants of the vehicle.

The ICAM model forms a practical way to analyse both the errors and human factors involved in this incident.

Analysis Overview

The basic cause of the incident was that the driver failed to maintain adequate control of the vehicle.

There are a number of contributing factors that exacerbated this:

  • The driver operated the vehicle at an inappropriate speed for the road conditions.

  • 4WD training provided to site staff and contractors is a one-off training course and there is no ongoing Verification of Competency (VOC) process.

  • The 4WD training package provides insufficient emphasis on driving techniques for wet gravel roads and role of passengers as a secondary defence in speaking up when concerned about safety.

  • The passengers in the vehicle did not identify the hazards about the speed of the vehicle given the wet road conditions.

Individual/Team Actions- These are the errors or violations that led directly to the incident. They must be ‘active failures’ – something that a person(s) did (or failed to do) in the presence of the hazard (driving) that directly led to the event?

So in the case of the vehicle incident; who did or did not do something that led to the driver losing directional control of the vehicle?

Using the ICAM methodology, let's have a closer look at the human errors and human factors involved based upon the evidence.

  • IT3 Operating Speed: The driver operated the vehicle at an inappropriate speed for the road conditions. While the driver was not exceeding the 110km/h posted speed limit, the driver by choosing to operate the vehicle at 100 km/h, through standing pools of water on the road, is evidence of not driving to the current road conditions.