Human factors error recovery

The final element in management s communication of a desire to reduce human error is the identification and elimination of error-likely situations. Every task is an opportunity for a human error, but some situahons represent greater risks than others. Identifying these high-risk situations is not easy and an expertise in applying human factors principles to the workplace is an essential prerequisite for this identification. Eliminating these hazardous situations is often relatively simple once they have been identified. In some cases it may be appropriate to provide error-tolerant systems, which are those that facilitate identification of and recovery from the errors. 

While these are useful aids to operation, neither the systems themselves nor the human interface with them are designed or managed in accordance with BS EN 61511. Therefore the credit to be taken for them should be limited. As they also typically rely on the same operator who has to bring the transfer to a stop, it is not appropriate for them to be considered as a protection layer. Instead they may be considered as a contributing factor to the reliability claimed for the operator, for example in relation to error recovery, in carrying out the basic process control function, and are therefore part of the basic process control system. 

It is now recognized that many errors in routine interactive behaviour are not the product of some stochastic process, and that causal explanations of human error can be developed [1]. However, little is known about what factors influence an individual s ability to recognize errors. Recognition that an error has been made is a prerequisite for error recovery. The focus of this paper is on this recognition process rather than the error recovery process as a whole. 

In the previous chapter, a comprehensive description was provided, from four complementary perspectives, of the process of how human errors arise during the tasks typically carried out in the chemical process industry (CPI). In other words, the primary concern was with the process of error causation. In this chapter the emphasis will be on the why of error causation. In terms of the system-induced error model presented in Chapter 1, errors can be seen as arising from the conjunction of an error inducing environment, the intrinsic error tendencies of the human and some initiating event which triggers the error sequence from this imstable situation (see Figure 1.5, Chapter 1). This error sequence may then go on to lead to an accident if no barrier or recovery process intervenes. Chapter 2 describes in detail the characteristics of the basic human error tendencies. Chapter 3 describes factors which combine with these tendencies to create the error-likely situation. These factors are called performance-influencing factors or PIFs. 

Checks of critical process parameters and warnings about hazardous conditions that can cause injury or equipment damage are important factors which determine the occurrence and recovery of human error. The purpose of these checks is to emphasize critical process information. Because of the critical nature of this information, checks and warning should be highlighted in a way that distinguishes them from other notes, and should be located where process workers will not overlook them. 

During the PHEA stage, the analyst has to identify likely human errors and possible ways of error detection and recovery. The PHEA prompts the analyst to examine the main performance-influencing factors (PIFs) (see Chapter 3) which can contribute to critical errors. All the task steps at the bottom level of the HTA are analyzed in turn to identify likely error modes, their potential for recovery, their safety or quality consequences, and the main performance-influencing factors (PIFs) which can give rise to these errors. In this case study, credible errors were found for the majority of the task steps and each error had multiple causes. An analysis of two operations from the HTA is presented to illustrate the outputs of the PHEA. Figure 7.12 shows a PHEA of the two following tasks Receive instructions to pump and Reset system. 

Step 6. Having identified such structural factors (the real root causes), the model must allow interpretation of these, i.e. it must suggest ways of influencing these factors, to eliminate or diminish error factors and to promote or introduce recovery opportunities in the human-machine systems and indeed in the organisation as a whole. 

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