Human factors task analysis process

The process for the specification of human subsystem safety requirements is no different to software or hardware although it is ai uably considerably harder due to the difficulties associated with the immense scope and variety of issues affecting the reliable performance of human tasks. This paper has examined issues relating to the consideration of human subsystem safety and has outlined the scope and activities necessary for a comprehensive human factors safety analysis. A pragmatic method was introduced that advocates the application of focused Human Factors techniques to the assurance of safety for human subsystems. 

In the course of assessing your company s current PSM status, you and your team have almost certainly gained a clear sense of which facilities pose the greatest risk, whether by virtue of inherent process hazards, human factors, management systems, or a combination. As you set priorities for implementation you should closely review information gleaned from the assessment tasks. In addition, you should try to validate or flesh out your impressions through some more quantitative analysis that can help to identify priority facilities. 

The first component of the systems approach to error reduction is the optimization of human performance by designing the system to support human strengths and minimize the effects of human limitations. The hiunan factors engineering and ergonomics (HFE/E) approach described in Section 2.7 of Chapter 2 indicates some of the techniques available. Design data from the human factors literature for areas such as equipment, procedures, and the human-machine interface are available to support the designer in the optimization process. In addition the analytical techniques described in Chapter 4 (e.g., task analysis) can be used in the development of the design. 

Human Factors Engineering/Ergonomics approach (control of error by design, audit, and feedback of operational experience) Occupational/process safety Manual/control operations Routine operation Task analysis Job design Workplace design Interface design Physical environment evaluation Workload analysis Infrequent... 

The term Task Analysis (TA) can be applied very broadly to encompass a wide variety of human factors techniques. Nearly all task analysis techniques provide, as a minimum, a description of the observable aspects of operator behavior at various levels of detail, together with some indications of the structure of the task. These will be referred to as action oriented approaches. Other techniques focus on the mental processes that imderlie observable behavior, for example, decision making and problem solving. These will be referred to as cognitive approaches. 

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. 

The human inspection models of visual search and human decision making were shown to be particularly applicable leading to a task analytic framework using hierarchical task analysis (HTA). In this way, human factors knowledge could be applied systematically to observed FPI processes. Visits were made to several engine repair facilities owned by major air carriers and engine manufac-... 

In step 1, the task data required for the analysis are defined. The major factors involved in determining data needs are (1) the scope of design problems being addressed (i.e., the functional scope of the human-machine-task system being analyzed), (2) the point in the engineering process at which the analysis is conducted, and (3) the extent to which the product is new or being revised. Task analysis can be applied to existing systems or to proposed systems for which tasks themselves need to be defined. 

It is fundamental for assessing human error in systems analyses to identify and describe the human acts with importance for the event sequence under analysis (qualitative assessment). This corresponds to the task analyses, which are characteristic of ergonomic studies. Firstly, the important actions, the moment in time at which they are required and the time period available for their execution have to be determined. Furthermore, the requirements for the action, the information necessary, respectively available, the possibilities of correction in case of omission or faulty execution must be estabhshed. Additionally, other factors of important influence on human reliabihty such as the state of knowledge on the process in question, ergonomically favourable or disadvantageous layout of the workplace, the tools or the environment are identihed. On the basis of this task analysis reliability data (normally failure probabilities on demand) are assigned to the tasks identified. They stem from existing data collections (cf. Table 9.21). 

The VIRTHUALIS methodology includes a suite of hiunan factors and risk analysis tools aimed at assessing the risk level of several initiating events. The main objective is to improve the risk analysis process through a validation of assessments made by safety analysts and the collection of empirical data about human performance (e.g., estimates of task duration). For this reason, a Virtual Environment Lab has been developed that simulates the technical system behaviour and the performance of operator tasks in a realistic manner. Operators are able to manipulate... 

The Human Factors analysts needed an approach and a tool to help them in providing a template for the interview process of a Task analysis with the ability to structure the interview phase in order to highlight and examine the deviations from standard practice. These deviations are fundamental to understanding what can and does go wrong in the field and should be an integral part of any safety critical task representation. A graphical representation of the procedure map linked to the template including ... 

The issue related to this UML modeling tools is that its usage for Human Factors Practitioners and Safety analysts is not so immediate because it is meant to be used primarily by software developers. Furthermore no support is provided for guiding the task analysis interview process. 

In this paper, we introduced a technique for analyzing tasks of en route ATC using the framework of distributed cognition as an approach to study problems of human factors in an ATC system. The analysis method of team cooperative work combines the concepts of TSA and mutual behef, and an ethnographical study. Moreover, we developed a method of visualization for team cooperative work from cognitive process perspective. 

The control room should utilize CRT displays and other advanced display technologies. It should be designed only after a full analysis has been made of the control tasks to be performed, and should provide means for data gathering and processing which support operator tasks and decision making. Human factors princples and criteria should be applied to work space, work environment, annunciator warning systems, panel layout and control-display integration. 

The task analysis technique has been developed mainly to handle human factors (in HAZID and other methods). In HAZID this is helpful in addressing human factors such as human error, man—machine interface, and procedural error. Of the various hazard identification techniques, task analysis is one of the most important. The other techniques are discussed in subsequent chapters, but here discussions will be on task analysis. Task analysis is the study of what users need to do, in terms of actions and/or cognitive processes, to achieve a task objective. There are several factors, such as task duration, repetitive frequency, task allocation, complexity, equipment, ambience, and environmental conditions, which are required for the task and they very much influence the performance. At times, tasks are often used interchangeably with process. 

Various human factors methods can be used to inform the TNA process. These include task analysis (e.g., HTA), cognitive task analysis (e.g., CDM), Cognitive Work Analysis (CWA) (Vicente, 1999), interviews, questionnaires, and observational studies. A summary of HTA, cognitive task analysis, and cognitive work analysis... 

---