Human error concepts

Initial Costs Demolition Costs Maintenance Costs Chances of Failure-in Limit States random hazards human error concept deficiency Direct costs of each type of failure Indirect consequences of each type of failure (e.g, H.A.C., boxgirders)... 

A related concept to inherently safer design is user-friendly design designing equipment so that human error or equipment failure does not have serious effects on safety (and also on output or efficiency). While we try to prevent human errors and equipment failures, only very low failure rates are acceptable when we are handling hazardous materials, and, as this book has shown, it is hard to achieve them. We should, therefore, try to design so that the effects of errors are not serious. The follov,/-ing are some of the ways in which we can accomplish this ... 

The cognitive approach has had a major influence in recent years on how human error is treated in systems such as chemical process plants and nuclear power generation. In the next section we shall describe some of the key concepts that have emerged from this work, and how they apply to the analysis of error in the CPI. Discussion of the cognitive view of human performance are contained in Reason (1990), Hollnagel (1993), Kantowitz and Fujita (1990), Hollnagel and Woods (1983), and Woods and Roth (1990). 

In addition to the proactive uses of the SRK model described in the two previous sections, it can also be employed retrospectively as a means of identifying the underlying causes of incidents attributed to human error. This is a particularly useful application, since causal analyses can be used to identify recurrent vmderlying problems which may be responsible for errors which at a surface level are very different. It has already been indicated in Section 2.4.1 that the same observable error can arise from a variety of alternative causes. In this section it will be shown how several of the concepts discussed up to this point can be combined to provide a powerful analytical framework that can be used to identify the root causes of incidents. 

The previous sections have presented an extensive description of some of the central concepts from the cognitive modeling perspective. These topics have been dealt with in some depth because they provide a comprehensive basis for the reduction of human error in the CPI. 

Systemic safety management especially prominent after a major organisational disaster, which forces the organisation to take a fundamental look at its entire safety philosophy the appropriate view of human error is the system-induced error concept, which says that many human errors can be... 

Human reliability (HR) and human error (HE) are positive and negative name. The concept of human reliability is drawn from the product... 

Human error can be divided into the general categories of slips and mistakes [143, 144]. Basic to the difference is the concept of intention or desired action. A mistake is an error in the intention, that is, an error that occurs during the planning of an action. A slip, on the other hand, is an error in carrying out the intention. As an example, suppose an operator decides to push button A. If the operator instead pushes button B, then it would be called a slip because the action did not match the intention. If the operator pushed A (carries out the intention correctly), but it turns out that the intention was wrong, that is, button A should not have been pushed, then this is called a mistake. 

To minimize the possibility of human error in any procedure involving a nuclear device, the U.S. Department of Defense has developed the two-person concept. Two or more persons, each capable of undertaking the prescribed task and of detecting an incorrect or unauthorized step in a procedure, are assigned to the task. One person accomplishes the procedural step and the other checks the action to verify it has been done correctly. It is not necessary that both persons have equal knowledge of the task, only that each is able... 

Until a few years ago, it was widely believed that if a worker was involved in an accident while performing their duties, it was probably the worker s fault. In a review of 75,000 accident cases, an estimated 88 percent of the accidents were due to unsafe acts of people. Similarly, airplane accidents were generally assumed due to human error— the pilot. U.S. Air Force ballistic missiles introduced a new concept of the cause of accidents. When the missiles were launched and then failed, there was no human on board to blame. Thus, the cause of the accident was due to something else, such as design or manufacturing error. This led to the new concept that accidents could be caused by an error due to ... 

In the previous paragraph, it was mentioned that in the past 88 percent of accidents were due to unsafe acts by the worker. Today, if those accidents were re-examined using the new concept, the data might say that 88 percent of the accidents were due to causes other than human error. This concept led to the OSHA Act, which attempts to reduce the number and severity of accidents by making equipment and procedures safer by mandatory means. 

An important element of prevention is the concept of designing the process to be error free through error proofing (the Japanese call it pokayoke or bakayoke). A widely used form of error proofing is the design (or redesign) of the machines and tools (the hardware ) so as to make human error improbable or even impossible [p. 347]. 

The concept of the "well designed system" was also presented in Chapter 3. A simplistic definition of such a system would be one where aU the techniques and measures presented in our functional safety standards to prevent systematic failures are followed. These techniques and measures are planned to significantly reduce the chance of a systematic fault to a tolerable level. Therefore, systematic failure rates caused by human error including failures due to installation errors, failures due to calibration errors and failures due to choosing equipment not suited for purpose are not included in the calculation. 

Rasmussen, J. (2000) The concept of human error. Is it useful for the design of safe systems in healthcare, in Safety in Medicine (eds C.A. Vincent and B. de Mol), Elsevier, Oxford. 

Notice, however, that in this present case we are interested in human reliability modeling. As a result the values for conditional probabilities mentioned above are obtained from the opinions of experts, and it has to be kept in mind that reliable data is not easy to obtain in this kind of problem concerning the installation of optical monitoring system in onshore oil well. Therefore, in order to use the elicitation method most accessible to experts, in this paper a fuzzy approach is adopted. Using fuzzy numbers, one can consider the linguistic variables adopted by the experts. The next section presents the main concepts of fuzzy logic and the arithmetic operations related to fuzzy numbers, which will be used to calculate human error probabihty. 

Turning to the model, for the interactions between the different performance factors and human error probability, as mentioned above, the concept of Bayesian networks is adopted (Droguett et al. 2006). 

In this paper we presented an approach where fuzzy logic and BBN concepts are combined to estimate human error probability. This combination leads to a fuzzy Bayesian network approach based on the concept o fuzzy number and on extension principles applied to discrete fuzzy probabilities calculation. 

Literature has many theories and concepts discussing human reliability and associated human error causal factors that always trigger incidents and accidents within safety-critical systems. The main - by definition - characteristics of such safety occurrences are their randonmess, rare predictability, sophisticated, yet vague sequence of propagation. Such characteristics can basically allow for the retrospective analysis of these occurrences and their causes at various sectors and levels within industry such that re-occurrence margins are reduced if not totally eliminated. The major drawback of such reactive treatment... 

The concept of human error, whether intentional or unintentional, is defined as (Lorenzo 1990) ... 

Consideration of deviation Did the maintenance program make allowances for human errors Was a two-person concept used for critical operations Did supervision monitor difficult, tedious, or other error-prone tasks ... 

A technique for predicting the potential for human error in an activity. It evalnates quantitatively the contribution of the human error component in the development of an untoward system. Special emphasis is placed on the human component in prodnct degradation. THERP involves the concept of basic error rate that is relatively consistent between tasks requiring similar human performance elements in different situations. Basic error rates are assessed in terms of contributions to specific system faUutes. 

Today, various mathematics and probability concepts are being used to study various types of safety-related problems. For example, probability distributions are used to represent times to human error in performing various types of time-continuous tasks in the area of safety [3-7]. In addition, the Markov method is used to conduct human performance reliability analysis in regard to engineering systems safety [7-9]. 

Human errors can be reduced substantially by making human factors an integral part of the medical device/equipment development process (i.e., right from the concept phase to the production phase) as shown in Figure 9.2 [24],... 

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