Everyone can make errors no matter how well trained and motivated they are. However in the workplace, the consequences of such human failure can be severe. Analysis of accidents and incidents shows that human failure contributes to almost all accidents and exposures to substances hazardous to health. Many major accidents e.g. Texas City, Piper Alpha, Chernobyl, were initiated by human failure. In order to avoid accidents and ill-health, companies need to manage human failure as robustly as the technical and engineering measures they use for that purpose.
The challenge is to develop error tolerant systems and to prevent errors from initiating; to manage human error proactively it should be addressed as part of the risk assessment process, where:
This Key Topic is also very relevant when trying to learn lessons following an incident or near miss. This also involves identifying the human errors that led to the accident and those factors that made such errors more likely – PIFs .
It is important to be aware that human failure is not random; understanding why errors occur and the different factors which make them worse will help you develop more effective controls. There are two main types of human failure: errors and violations.
A human error is an action or decision which was not intended. A violation is a deliberate deviation from a rule or procedure. HSG 48 provides a fuller description of types of error, but the following may be a helpful introduction.
Some errors are slips or lapses, often “actions that were not as planned” or unintended actions. They occur during a familiar task and include slips (e.g. pressing the wrong button or reading the wrong gauge) and lapses (e.g. forgetting to carry out a step in a procedure). These types of error occur commonly in highly trained procedures where the person carrying them out does not need to concentrate on what they are doing. These cannot be eliminated by training, but improved design can reduce their likelihood and provide a more error tolerant system.
Other errors are Mistakes or errors of judgement or decision-making where the “intended actions are wrong” i.e. where we do the wrong thing believing it to be right. These tend to occur in situations where the person does not know the correct way of carrying out a task either because it is new and unexpected, or because they have not be properly trained (or both). Often in such circumstances, people fall back on remembered rules from similar situations which may not be correct. Training based on good procedures is the key to avoiding mistakes.
Violations (non-compliances, circumventions, shortcuts and work-arounds) differ from the above in that they are intentional but usually well-meaning failures where the person deliberately does not carry out the procedure correctly. They are rarely malicious (sabotage) and usually result from an intention to get the job done as efficiently as possible. They often occur where the equipment or task has been poorly designed and/or maintained. Mistakes resulting from poor training (i.e. people have not been properly trained in the safe working procedure) are often mistaken for violations. Understanding that violations are occurring and the reason for them is necessary if effective means for avoiding them are to be introduced. Peer pressure, unworkable rules and incomplete understanding can give rise to violations. HSG48 provides further information.
There are several ways to manage violations, including designing violations out, taking steps to increase their detection, ensuring that rules and procedures are relevant/practical and explaining the rationale behind certain rules. Involving the workforce in drawing up rules increases their acceptance. Getting to the root cause of any violation is the key to understanding and hence preventing the violation.
This aide-memoire on Human Failure Types explains in more detail, along with examples and typical control measures.
Understanding these different types of human failure can help identify control measures but you need to be careful you do not oversimplify the situation. In some cases it can be difficult to place an error in a single category – it may result from a slip or a mistake, for example. There may be a combination of underlying causes requiring a combination of preventative measures. It may also be useful to think about whether the failure is an error of omission (forgetting or missing out a key step) or an error of commission (e.g. doing something out of sequence or using the wrong control), and taking action to prevent that type of error.
The likelihood of these human failures is determined by the condition of a finite number of ‘performance influencing factors’ , such as design of interfaces, distraction, time pressure, workload, competence, morale, noise levels and communication systems.
There is more to managing human failure in complex systems than simply considering the actions of individual operators. However, there is obvious merit in managing the performance of the personnel who play an important role in preventing and controlling risks, as long as the context in which this behaviour occurs is also considered.
When assessing the role of people in carrying out a task, be careful that you do not:
Companies should consider whether any of the above apply to how their organisation manages human factors.
Human Failure Aide Memoire – This aide memoire gives more information about the different failure types and appropriate control measures.
Reducing error and influencing behaviour (HSG48), HSE Books 1999, ISBN 0 7176 2452 8. Essential HSE generic industry guidance on human factors - a simple introduction.
Briefing Note 3: Humans and Risk