The H factor

Dr Ian Randle, President-Elect of the Chartered Institute of Ergonomics & Human Factors (CIEHF) and Managing Director of Hu-Tech Human Factors asks: Is human error avoidable?

Human error has been implicated in the great majority of major industrial accidents. Investigations may end with a conclusion of human error as if this is something that can’t be avoided or prevented. However from a Human Factors (HF) perspective this marks the beginning of the investigation, where work is done to identify the causes behind the human error and find means to prevent recurrence. Humans by our very nature are unreliable and make mistakes, and we will never eliminate all errors in the operation of complex systems. The objective is to help ensure that individuals are never put in a position where a simple error or combination of errors will have a catastrophic outcome.

Human Factors is the scientific study of how people interact with equipment and work systems. HF uses similar methods for modelling human failure as process engineers apply to modelling equipment failure. The aim is to identify critical errors and to eliminate them or mitigate their consequences.

This is where a deeper understanding of the type and cause of error is essential. The UK Health & Safety Executive (HSE) has identified four main types of human error: slips (unintended actions), lapses (lack of appropriate action), mistakes (knowledge-based errors), and intentional violations. Each has different causes and requires different solutions. Training can form part of the solution for knowledge-based errors but may be ineffective in preventing slips. An example of a slip is misdialling a routinely used telephone number – extra training won’t eliminate the error, however a better designed interface with clear and consistent labelling will help. Lapses are often caused by distractions, having to divide attention between concurrent tasks, and by fatigue. Ensuring that the task and workload is designed to minimise distractions during critical procedures, and effective shift-management to minimise fatigue are appropriate strategies in such cases.

Major accidents are seldom caused by a single human error; they are normally the consequence of a series of errors and a certain set of conditions. However, HF analysis can be effective in identifying safety critical operations and where high levels of human performance are essential in maintaining barriers to major accident risks.

HAZOP and Bowtie analysis are good sources of identifying such situations. Any operating procedures that form part of the safeguard or barrier against a major accident risk can be thought of as a safety critical task. The objective will be to eliminate these where possible and to replace the human in the loop with engineering safeguards. For example, responding to a high-level alarm requires an operator to detect the alarm, determine the appropriate response and then execute the response correctly. This gives a number of opportunities for human error and makes the system significantly less reliable than an engineered safeguard.

It is not feasible or cost-effective to completely eliminate human-based safeguards. Where critical tasks cannot be eliminated, a structured human error analysis is undertaken on the associated tasks and procedure. The objective is to determine where errors that could have critical consequences can occur, and to devise practical means to reduce the likelihood or consequence. This can be via error-tolerant interface designs as well as well-designed operating procedures and additional checks.

It is important to note that people not should be seen just as a potential source of error but also as an important part of the system integrity; it is their intelligence and adaptability that makes them able to identify problems and intervene when processes are going wrong. The human operator will therefore never be completely eliminated from the operation of complex process plant.

Piper Alpha, Texas City, Buncefield and Macondo are all incidents, which are associated with a combination of technical and human failures. Whilst significant advances have been made in technical and process safety engineering, it is clear that it will not be possible to prevent future major incidents without also considering the human failures. Human Factors therefore needs to be an integral part of safety engineering with the same degree of attention paid to analysing and designing the human safeguards as is the case for engineering safeguards. The oil/gas industry has some way to go before this becomes a reality, however, increasing awareness and regulations on human factors contributions to major accident risks means that the industry is moving in the right direction.

Dr Ian Randle will be joined by Professor Ron McCloud, ex-Head of Human Factors at Shell, to discuss human factors in barriers to major accident risk at the Ergonomics & Human Factors 2016 Conference at Staverton Park this April. To reserve your place, please visit

The Chartered Institute of Ergonomics and Human Factors (CIEHF) is a UK-based professional body with over 1700 members. CIEHF members are practitioners, researchers and students working or studying in ergonomics and human factors or a related field. The CIEHF sets and maintains standards, provides resources, and promotes networking and communication among members and organisations that have an interest in ergonomics and human factors.

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