Human error rule-based

A relatively simple model has been developed by Rasmussen to quantify human error rates based on the level of training (Rasmussen (1979, 1981)). This model divides the behaviour into three basic categories skill-based, rule-based, and knowledge-based behaviours. 

Many organizations that have evolved over a long period of time come to believe that the system of safety rules that they have developed is invulnerable to human error. The existence of a "rule book" culture can produce a complacent attitude which assumes that if the rules are followed then accidents are impossible. This is based on the belief that a rigid set of rules will cover every contingency and that interpretation by individuals to cover imanticipated situations will never be required. Of course, all rules will at some time require such interpretation, and the need for this should be accepted and built into the system. 

As was discussed in Chapter 2 Rasmussen has provided the basic model of human error based on three levels of behaviour skill-, rule- and knowledge-based (S-B, R-B, K-B). This SRK model has been operationalised to describe operator errors in process control tasks by combining it with characteristic task elements, which as a whole cover the entire spectrum of operator subtasks. 

The human factors literature is rich in task analysis techniques for situations and jobs requiring rule-based behavior (e.g., Kirwan and Ainsworth 1992). Some of these techniques can also be used for the analysis of cognitive tasks where weU-practiced work methods must be adapted to task variations and new circumstances. This can be achieved provided that task analysis goes beyond the recommended work methods and explores task variations that can cause failures of human performance. Hierarchical task analysis (Shepherd 1989), for instance, can be used to describe how operators set goals and plan their activities in terms of work methods, antecedent conditions, and expected feedback. When the analysis is expanded to cover not only normal situations but also task variations or changes in circumstances, it would be possible to record possible ways in which humans may fail and how they could recover from errors. Table 2 shows an analysis of a process control task where operators start up an oil refinery furnace. This is a safety-critical task because many safety systems are on manual mode, radio communications between control room and on-site personnel are intensive, side effects are not visible (e.g., accumulation of fuel in the fire box), and errors can lead to furnace explosions. 

Skills, rules, and knowledge model Models human information processing in terms of three levels of behavioral control skill based, rule based, and knowledge based Models the processes and requirements for each level of behavior Can be used with quantitative models of human performance to estimate task time and errors... 

Norman, Donald A. (April 1983). Design rules based on analyses of human error. Communications of the ACM 26 (4) 254-258. 

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

Work procedures Studies have showed that 11 to 24% industrial accidents occurred due to lack and weaknesses related in procedures (Peterson 1996). Rasmussen s classified these errors as rule based errors (Kirwan 1997). In this study, some of human errors identified in the PHEA worksheets, were because of shortcomings in... 

Other authors like Jens Rasmussen ([14], [15]) distinguish between different levels of human performance and correlate them to required attention and familiarity with the task, cf. Fig.5. It is evident that knowledge-based actions are associated with the highest error probability, but most actions required from a car driver are rule based like obeying traffic signs, or skill-based like changing the gears. 

The classification of human error within the FASGEP project takes into account the woric of Rasmussen, specifically the classification of Rule-Based errors, Skill-Based errors, and Knowledge-Based errors. The causal relationships for each of the classifications have been developed into a causal network. A type of graphical probability model is based on this. 

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