Human reliability
Encyclopedia
Human reliability is related to the field of human factors engineering
Human factors engineering
Human Factors Engineering is the discipline of applying what is known about human capabilities and limitations to the design of products, processes, systems, and work environments. It can be applied to the design of all systems having a human interface, including hardware and software...

 and ergonomics, and refers to the reliability of human
Human
Humans are the only living species in the Homo genus...

s in fields such as manufacturing
Manufacturing
Manufacturing is the use of machines, tools and labor to produce goods for use or sale. The term may refer to a range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale...

, transport
Transport
Transport or transportation is the movement of people, cattle, animals and goods from one location to another. Modes of transport include air, rail, road, water, cable, pipeline, and space. The field can be divided into infrastructure, vehicles, and operations...

ation, the military
Military
A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...

, or medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

. Human performance
Performance
A performance, in performing arts, generally comprises an event in which a performer or group of performers behave in a particular way for another group of people, the audience. Choral music and ballet are examples. Usually the performers participate in rehearsals beforehand. Afterwards audience...

 can be affected by many factors such as age
Senescence
Senescence or biological aging is the change in the biology of an organism as it ages after its maturity. Such changes range from those affecting its cells and their function to those affecting the whole organism...

, state of mind, physical health
Health
Health is the level of functional or metabolic efficiency of a living being. In humans, it is the general condition of a person's mind, body and spirit, usually meaning to be free from illness, injury or pain...

, attitude
Attitude (psychology)
An attitude is a hypothetical construct that represents an individual's degree of like or dislike for something. Attitudes are generally positive or negative views of a person, place, thing, or event— this is often referred to as the attitude object...

, emotion
Emotion
Emotion is a complex psychophysiological experience of an individual's state of mind as interacting with biochemical and environmental influences. In humans, emotion fundamentally involves "physiological arousal, expressive behaviors, and conscious experience." Emotion is associated with mood,...

s, propensity for certain common mistakes, error
Error
The word error entails different meanings and usages relative to how it is conceptually applied. The concrete meaning of the Latin word "error" is "wandering" or "straying". Unlike an illusion, an error or a mistake can sometimes be dispelled through knowledge...

s and cognitive bias
Cognitive bias
A cognitive bias is a pattern of deviation in judgment that occurs in particular situations. Implicit in the concept of a "pattern of deviation" is a standard of comparison; this may be the judgment of people outside those particular situations, or may be a set of independently verifiable...

es, etc.

Human reliability is very important due to the contributions of humans to the resilience
Resilience (network)
In computer networking: “Resilience is the ability to provide and maintain an acceptable level of service in the face of faults and challenges to normal operation.”These services include:* supporting distributed processing* supporting networked storage...

 of systems and to possible adverse consequences of human errors or oversights, especially when the human is a crucial part of the large socio-technical systems
Socio-technical systems
Sociotechnical systems in organizational development is an approach to complex organizational work design that recognizes the interaction between people and technology in workplaces. The term also refers to the interaction between society's complex infrastructures and human behaviour...

 as is common today. User-centered design
User-centered design
In broad terms, user-centered design or pervasive usability is a design philosophy and a process in which the needs, wants, and limitations of end users of a product are given extensive attention at each stage of the design process...

 and error-tolerant design
Error-tolerant design
An error-tolerant design is one that does not unduly penalize user errors. It is the human equivalent of fault tolerant design that allows equipment to continue functioning in the presence of hardware faults, such as a "limp-in" mode for an automobile electronics unit that would be employed if...

 are just two of many terms used to describe efforts to make technology
Technology
Technology is the making, usage, and knowledge of tools, machines, techniques, crafts, systems or methods of organization in order to solve a problem or perform a specific function. It can also refer to the collection of such tools, machinery, and procedures. The word technology comes ;...

 better suited to operation by humans.

Human reliability analysis techniques

A variety of methods exist for human reliability analysis (HRA). Two general classes of methods are those based on probabilistic risk assessment
Probabilistic risk assessment
Probabilistic risk assessment is a systematic and comprehensive methodology to evaluate risks associated with a complex engineered technological entity ....

 (PRA) and those based on a cognitive theory of control
Control theory
Control theory is an interdisciplinary branch of engineering and mathematics that deals with the behavior of dynamical systems. The desired output of a system is called the reference...

.

PRA-based techniques

One method for analyzing human reliability is a straightforward extension of probabilistic risk assessment
Probabilistic risk assessment
Probabilistic risk assessment is a systematic and comprehensive methodology to evaluate risks associated with a complex engineered technological entity ....

 (PRA): in the same way that equipment can fail in a plant, so can a human operator commit errors. In both cases, an analysis (functional decomposition
Functional decomposition
Functional decomposition refers broadly to the process of resolving a functional relationship into its constituent parts in such a way that the original function can be reconstructed from those parts by function composition...

 for equipment and task analysis
Task analysis
Task analysis is the analysis of how a task is accomplished, including a detailed description of both manual and mental activities, task and element durations, task frequency, task allocation, task complexity, environmental conditions, necessary clothing and equipment, and any other unique factors...

 for humans) would articulate a level of detail for which failure or error probabilities can be assigned. This basic idea is behind the Technique for Human Error Rate Prediction
Technique for Human Error Rate Prediction
Technique for Human Error Rate Prediction is a technique used in the field of Human reliability Assessment , for the purposes of evaluating the probability of a human error occurring throughout the completion of a specific task...

 (THERP). THERP is intended to generate human error probabilities that would be incorporated into a PRA. The Accident Sequence Evaluation Program (ASEP) human reliability procedure is a simplified form of THERP; an associated computational tool is Simplified Human Error Analysis Code (SHEAN). More recently, the US Nuclear Regulatory Commission has published the Standardized Plant Analysis Risk (SPAR) human reliability analysis method also because of human error.

Cognitive control based techniques

Erik Hollnagel has developed this line of thought in his work on the Contextual Control Model (COCOM) and the Cognitive Reliability and Error Analysis Method (CREAM
CREAM
CREAM is a human reliability analysis technique developed by Erik Hollnagel. It is a bi-directional analysis method, meant to be used for both performance prediction and accident analysis...

). COCOM models human performance as a set of control modes—strategic (based on long-term planning), tactical (based on procedures), opportunistic (based on present context), and scrambled (random) - and proposes a model of how transitions between these control modes occur. This model of control mode transition consists of a number of factors, including the human operator's estimate of the outcome of the action (success or failure), the time remaining to accomplish the action (adequate or inadequate), and the number of simultaneous goals of the human operator at that time. CREAM is a human reliability analysis method that is based on COCOM.

Related techniques

Related techniques in safety engineering
Safety engineering
Safety engineering is an applied science strongly related to systems engineering / industrial engineering and the subset System Safety Engineering...

 and reliability engineering
Reliability engineering
Reliability engineering is an engineering field, that deals with the study, evaluation, and life-cycle management of reliability: the ability of a system or component to perform its required functions under stated conditions for a specified period of time. It is often measured as a probability of...

 include failure mode and effects analysis
Failure mode and effects analysis
A failure modes and effects analysis is a procedure in product development and operations management for analysis of potential failure modes within a system for classification by the severity and likelihood of the failures...

, hazop
Hazop
A hazard and operability study is a structured and systematic examination of a planned or existing process or operation in order to identify and evaluate problems that may represent risks to personnel or equipment, or prevent efficientoperation....

, fault tree, and SAPHIRE
SAPHIRE
SAPHIRE is a probabilistic risk and reliability assessment software tool. SAPHIRE stands for Systems Analysis Programs for Hands-on Integrated Reliability Evaluations. The system was developed for the U.S...

: Systems Analysis Programs for Hands-on Integrated Reliability Evaluations.

Human Factors

Since the end of WWII human factors issues have become a paramount concern in aviation safety. It’s estimated that anywhere between 90% to 95% of aviation accidents and incidents are caused by human factors. But exactly what is considered a human factor? Human factors is an all encompassing effort to compile data about human capabilities and limitations and apply that data to equipment, systems, software, facilities, procedures, jobs, environments, training, staffing, and personnel management to produce safe comfortable, ergonomic and effective human performance. The FAA is currently making an effort to integrate human factors into all aspects of aviation where safety is a major concern. As a result the FAA issued FAA order 9550.8 which is a human factors policy that states the following:

Human factors shall be systematically integrated into the planning and execution of the functions of all FAA elements and activities associated with system acquisitions and system operations. FAA endeavors shall emphasize human factors considerations to enhance system performance and capitalize upon the relative strengths of people and machines. These considerations shall be integrated at the earliest phases of FAA projects.

The FAA has realized that when most individuals think of a system or project, they usually consider only the tangibles such as hardware, software and equipment. Most individuals fail to think about the end user of the product, the human being. Therefore during systems designing consideration for different aptitudes and abilities are never considered. The FAA’s combating this predominant thought pattern by the introduction of what is known as “Total System Performance”. Total System Performance is a measure of probability. The probability that the total system will perform correctly, when it is available, is the probability that the hardware/software will perform correctly, times the probability that the operating environment will not degrade the system operation, times the probability that the user will perform will perform correctly. It’s been discovered that a system can work perfectly in a test environment, demonstration site or laboratory and then not perform as well once the human being enters the loop as the operator. In order to compensate for this fact, human factors must be accounted for and integrated into new systems. By doing so there will be increased performance accuracy, decreased performance time and enhanced safety. FAA research has indicated that designing systems to improve human performance is cost effective and safe when done early in the developmental stages of a project. Some potential human factors to consider during research and development stages are functional design, safety and health, work space, display and controls, information requirements, display presentation, visual/aural alerts, communications, anthropometrics and environment.

Human error

Human error
Error
The word error entails different meanings and usages relative to how it is conceptually applied. The concrete meaning of the Latin word "error" is "wandering" or "straying". Unlike an illusion, an error or a mistake can sometimes be dispelled through knowledge...

 has been cited as a cause or contributing factor in disasters and accidents in industries as diverse as nuclear power (e.g., Three Mile Island accident
Three Mile Island accident
The Three Mile Island accident was a core meltdown in Unit 2 of the Three Mile Island Nuclear Generating Station in Dauphin County, Pennsylvania near Harrisburg, United States in 1979....

), aviation (see pilot error
Pilot error
Pilot error is a term used to describe the cause of an accident involving an airworthy aircraft where the pilot is considered to be principally or partially responsible...

), space exploration (e.g., Space Shuttle Challenger Disaster
Space Shuttle Challenger disaster
The Space Shuttle Challenger disaster occurred on January 28, 1986, when Space Shuttle Challenger broke apart 73 seconds into its flight, leading to the deaths of its seven crew members. The spacecraft disintegrated over the Atlantic Ocean, off the coast of central Florida at 11:38 am EST...

), and medicine (see medical error
Medical error
A medical error may be defined as a preventable adverse effect of care, whether or not it is evident or harmful to the patient. This might include an inaccurate or incomplete diagnosis or treatment of a disease, injury, syndrome, behavior, infection, or other ailment.-Definitions:As a general...

). It is also important to stress that "human error" mechanisms are the same as "human performance" mechanisms; performance later categorized as 'error' is done so in hindsight: therefore actions later termed "human error" are actually part of the ordinary spectrum of human behaviour. The study of absent-mindedness
Absent-mindedness
Absent-mindedness is where a person shows inattentive or forgetful behaviour. It can have three different causes:# a low level of attention...

 in everyday life provides ample documentation and categorization of such aspects of behavior. While human error is firmly entrenched in the classical approaches to accident investigation and risk assessment, it has no role in newer approaches such as resilience engineering.

Categories of human error

There are many ways to categorize human error.
  • exogenous versus endogenous (i.e., originating outside versus inside the individual)
  • situation assessment versus response planning and related distinctions in
    • errors in problem detection (also see signal detection theory)
    • errors in problem diagnosis (also see problem solving
      Problem solving
      Problem solving is a mental process and is part of the larger problem process that includes problem finding and problem shaping. Consideredthe most complex of all intellectual functions, problem solving has been defined as higher-order cognitive process that requires the modulation and control of...

      )
    • errors in action planning and execution (for example: slips or errors of execution versus mistakes or errors of intention)
  • By level of analysis; for example, perceptual (e.g., optical illusions) versus cognitive versus communication
    Interpersonal communication
    Interpersonal communication is usually defined by communication scholars in numerous ways, usually describing participants who are dependent upon one another. It...

     versus organizational
    Organizational studies
    Organizational studies, sometimes known as organizational science, encompass the systematic study and careful application of knowledge about how people act within organizations...

    .


The cognitive study of human error is a very active research field, including work related to limits of memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....

 and attention
Attention
Attention is the cognitive process of paying attention to one aspect of the environment while ignoring others. Attention is one of the most intensely studied topics within psychology and cognitive neuroscience....

 and also to decision making
Decision making
Decision making can be regarded as the mental processes resulting in the selection of a course of action among several alternative scenarios. Every decision making process produces a final choice. The output can be an action or an opinion of choice.- Overview :Human performance in decision terms...

 strategies such as the availability heuristic
Availability heuristic
The availability heuristic is a phenomenon in which people predict the frequency of an event, or a proportion within a population, based on how easily an example can be brought to mind....

 and other cognitive biases. Such heuristics and biases are strategies that are useful and often correct, but can lead to systematic patterns of error.

Misunderstandings as a topic in human communication have been studied in conversation analysis
Conversation analysis
Conversation analysis is the study of talk in interaction . CA generally attempts to describe the orderliness, structure and sequential patterns of interaction, whether institutional or in casual conversation.Inspired by ethnomethodology Conversation analysis (commonly abbreviated as CA) is the...

, such as the examination of violations of the cooperative principle
Cooperative principle
In social science generally and linguistics specifically, the cooperative principle describes how people interact with one another. As phrased by Paul Grice, who introduced it, it states, "Make your contribution such as it is required, at the stage at which it occurs, by the accepted purpose or...

 and Gricean maxims.

Organizational
Organizational studies
Organizational studies, sometimes known as organizational science, encompass the systematic study and careful application of knowledge about how people act within organizations...

 studies of error or dysfunction have included studies of safety culture
Safety culture
Safety culture is a term used to describe the way in which safety is managed in the workplace, and often reflects "the attitudes, beliefs, perceptions and values that employees share in relation to safety" .-Defining safety culture:...

. One technique for organizational analysis is the Management Oversight Risk Tree (MORT).

Human Factors Analysis and Classification System (HFACS)

See Human Factors Analysis and Classification System in Main article: National Fire Fighter Near-Miss Reporting System
National Fire Fighter Near-Miss Reporting System
The National Fire Fighter Near-Miss Reporting System was launched on August 12th 2005 by the International Association of Fire Chiefs. It was announced at a press conference in Denver, Colorado, after having completed a pilot program involving 38 fire departments across the country...


The Human Factors Analysis and Classification System (HFACS) was developed initially as a framework to understand "human error" as a cause of aviation accidents. It is based on James Reason's Swiss cheese model
Swiss cheese model
The Swiss cheese model is a organizational model, proposed by James Reason of the University of Manchester and Dante Orlandella, used to analyze the causes of systematic failures or accidents, commonly used in the fields of aviation, engineering and healthcare...

 of human error in complex systems. HFACS distinguishes between the "active failures" of unsafe acts, and "latent failures" of preconditions for unsafe acts, unsafe supervision, and organizational influences. These categories were developed empirically on the basis of many aviation accident reports.

"Unsafe acts" are performed by the human operator "on the front line" (e.g., the pilot, the air traffic controller, the driver). Unsafe acts can be either errors (in perception, decision making or skill-based performance) or violations (routine or exceptional). The errors here are similar to the above discussion. Violations are the deliberate disregard for rules and procedures. As the name implies, routine violations are those that occur habitually and are usually tolerated by the organization or authority. Exceptional violations are unusual and often extreme. For example, driving 60 mph in a 55-mph zone speed limit is a routine violation, but driving 130 mph in the same zone is exceptional.

There are two types of preconditions for unsafe acts: those that relate to the human operator's internal state and those that relate to the human operator's practices or ways of working. Adverse internal states include those related to physiology (e.g., illness) and mental state (e.g., mentally fatigued, distracted). A third aspect of 'internal state' is really a mismatch between the operator's ability and the task demands; for example, the operator may be unable to make visual judgments or react quickly enough to support the task at hand. Poor operator practices are another type of precondition for unsafe acts. These include poor crew resource management (issues such as leadership and communication) and poor personal readiness practices (e.g., violating the crew rest requirements in aviation).

Four types of unsafe supervision are: inadequate supervision; planned inappropriate operations; failure to correct a known problem; and supervisory violations.

Organizational influences include those related to resources management (e.g., inadequate human or financial resources), organizational climate (structures, policies, and culture), and organizational processes (such as procedures, schedules, oversight).

Controversies

Some researchers have argued that the dichotomy of human actions as "correct" or "incorrect" is a harmful oversimplification of a complex phenomena. A focus on the variability of human performance and how human operators (and organizations) can manage that variability may be a more fruitful approach. Newer approaches such as resilience engineering mentioned above, highlights the positive roles that humans can play in complex systems. In resilience engineering, successes (things that go right) and failures (things that go wrong) are seen as having the same basis, namely human performance variability. A specific account of that is the efficiency–thoroughness trade-off (ETTO) principle, which can be found on all levels of human activity, in individual as well as collective.

See also

  • Absolute probability judgement
    Absolute probability judgement
    Absolute probability judgement is a technique used in the field of human reliability assessment , for the purposes of evaluating the probability of a human error occurring throughout the completion of a specific task...

  • Latent human error
    Latent human error
    A Latent human error is a human error which is likely to be made due to systems or routines that are formed in such a way that humans are disposed to making these errors...

  • Human error assessment and reduction technique
    Human error assessment and reduction technique
    Human error assessment and reduction technique is a technique used in the field of human reliability assessment , for the purposes of evaluating the probability of a human error occurring throughout the completion of a specific task...

     (HEART), a technique used in the field of human reliability
  • Influence diagrams approach
    Influence diagrams approach
    Influence Diagrams Approach is a technique used in the field of Human reliability Assessment , for the purposes of evaluating the probability of a human error occurring throughout the completion of a specific task...


Further reading

http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1842/, IEEE Transactions on Systems, Man, and Cybernetics, Volume 26, No. 1, January 1996, 2-16}} http://www.laas.fr/IFIPWG/Workshops&Meetings/46/05-Harrison.pdf
  • CCPS, Guidelines for Preventing Human Error. This book explains about qualitative and quantitative methodology for predicting human error. Qualitative methodology called SPEAR: Systems for Predicting Human Error and Recovery, and quantitative methodology also includes THERP, etc.

Standards and guidance documents


Tools


Research labs


Media coverage


Networking

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