Human errors and violations

Human errors fall into three groups - slips, lapses and mistakes, which can be further sub-divided into rule-based and knowledge-based mistakes. 

These are very similar in that they are caused by a momentary memory loss often due to lack of attention or loss of concentration. They are not related to levels of training, experience or motivation and they can usually be reduced by re-designing the job or equipment or minimizing distractions. 

Slips are failures to carry out the correct actions of a task. Examples include the use of the incorrect switch, reading the wrong dial or selecting the incorrect component for an assembly. A slip also describes an action taken too early or too late within a given working procedure. 

Lapses are failures to carry out particular actions which may form part of a working procedure. A fork lift truck driver leaving the keys in the ignition lock of his truck is an example of a lapse as is the failure to replace the petrol cap on a car after filling it with petrol. Lapses may be reduced by re-designing equipment so that, 

Mistakes occur when an incorrect action takes place but the person involved believes the action to be correct. A mistake involves an incorrect judgement. There are two types of mistake - rule-based and knowledge-based. 

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In addition to the Chernobyl design deficiencies, there was evidence of human error and the voluntary violation of safety rules, both for production reasons and in the incorrect appreciation of the real danger. Chernobyl can with good reason be considered representative of the maximum possible accident to a power reactor. 

These are the conditions in existence immediately before or at the time of the incident that directly influence human and equipment performance in the workplace. These are the circirmstances under which the errors and violations took place and can be embedded in task demands, the work environmerrt, individttal capabilities and human factors. The Task/Environmental Conditions identified in the case study include ... 

Vinnem et al. 2012, Gran et al. 2012 Uses BBNs to estimate the impact of MOFs on three types of human error mistakes, violations and slips. Fault Trees and Event Trees are integrated into BBNs mode. Discusses a procedure to define and measure MOFs. MOFA... 

Human error as a simple catch-all explanation for accidents is now discredited. The term, if it means anything at all, does not provide an adequate description of the many ways in which the failure of people at all levels in organisations can contribute to the complex phenomenon we call an accident. It is more useful to think about human failure , which involves both errors and violations, and also to distinguish between active failures and latent failures. 

Reason has analysed the effects of an inadequate safety culture on the risk of accidents from a barrier perspective (Reason, 1998). The three conditions that he focuses on are found in the list above on safety-climate elements. First, a poor safety culture will increase the frequency of human errors and rule violations and thus also increase active barrier transgressions. Second, it will result in complacency and in unwillingness to check and maintain passive barriers adequately. Third, the organisation that is characterised by an inadequate safety climate will be unwilling to report and follow up near accidents and identified deficiencies in the barriers. 

Aslaiudes M, Valot C, Nyssen AS, Amalberti R (2007) Evolution of error and violation description in French air force accident reports impacts of human factors education. Hum Factors Aerosp Saf 6 51-70... 

Motivational campaigns are one way of dealing with routine violations (see Section 2.5.1.1). They are not directly applicable to those human errors which are caused by design errors and mismatches between the human and the task. These categories of errors will be discussed in more detail in later sections. 

When an accident report says that an accident was due to human error, the writer usually means an error by an operator or other front line worker. But designers and managers also make errors, not slips or lapses of attention as they usually have time to check their work, as well as mistakes or, less often, violations. 

Human failure can essentially be split into two categories circumstances in which our actions are unintentional and those which are deliberate. Inadvertent actions constitute human error whilst deliberate activities fall into the remit of violation. 

The error classification of the test and maintenance human errors involved in unplanned reactor trips showed that planning failure contributed most high to the human-related tmplanned reactor trip events (47%), and contribution of execution failure was also considerably high (33%). In the case of the problem from a work method or work object, the contribution was low against the overall events (19%) but it shows a distinctive feature that the events are strongly related to maintenance categories. Contribution of a rule violation was low as a whole. The results are summarized in Table 1. 

One of the major contributory factors in road accidents is human error (for example violation of speed limits). The type, size and frequency of these human errors depend on the whole road system and traffic regulations, which must be designed in a way to be safe and protective of such human errors. 

Anticipate human error, especially lapses and violations. It is part of the human condition and designers need to understand this. To not recognise this reality is like blaming gravity for falls. (Kerrabee)... 

Accident or mishap deviation models as used in system safety processes can permit analysis of events in terms of deviations. The value assigned to a system variable becomes a deviation whenever it falls outside an established norm. When measuring system variables, these deviations can assume different values depending on the situation. Hazard control policies and procedures should detail any specified requirements. A deviation from a specified requirement could result in a human error for failure to follow procedures. Therefore, we must consider incidental factors as deviations from an accepted practice. An unsafe act relates to a personal action that violates or deviates from a commonly accepted safe procedure. Time functions as the basic dimension in a system deviation... 

This paper describes an approach to the integrated assessment of human error, violations and safety culture which is intended to overcome some of the gaps which can exist when separate aspects of human factors are analysed in isolation. 

This paper describes the development of a tool set for incident investigation that incorporates the use of a suite of tools to assess human error, violations and safety culture as an integral part of the investigation. This approach helps to overcome issues associated with a delay in the investigation of human factors that can occur if such techniques are applied in a stand-alone context. This approach also has the benefit of collecting data on the human aspects of safety as a whole, rather than independently conducting several forms of analysis. This allows the complex relationships between people, the organisation, the environment and the task to be captured. 

Table 1 summarises the coverage of human factors afforded by the integration of safety culture, violations and human error analysis methodologies. 

There is sufficient evidence from well-known historical events to indicate that safety culture (Piper Alpha), human error (Kegworth) and violations (Herald of Free Enterprise) all play major roles in the occurrence of incidents. Coupled with the increasing importance being afforded to the human factors causes of incidents, organisations have a very convincing case for the development of an integrated suite of tools for incident investigators. 

Many organisations already use root cause analysis techniques that allow the identification of critical factors in the occurrence of incidents. For each critical factor, related behaviours can be isolated. A number of these factors can be related closely to human error, violation or safety culture. Formal approaches are required to perform in-depth analysis of such factors and determine the root of human factors problems and how they could be dealt with. 

Human failures in health and safety are either classified as errors or violations. An error is an unintentional deviation from an accepted standard, while a violation is a deliberate deviation from the standard (see Figure 4.7). 

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