Do you get the picture?: situation awareness and system safety

Studies of the dependency between complex, dynamic systems and their human operators often focus on human-computer interactions without considering the emergent properties of human-machine systems in use. As systems become more complex, and typical operating environments more dynamic, the role of the operator has typically changed from providing manual to cognitive control. An understanding of human cognition in context is thus central to the design of human-machine systems and this is particularly pertinent in safety-related systems when the elimination of hazards is a principal concern. This paper will argue that operator situation awareness is an important, safety-related phenomenon and that it can be used to examine human cognition in context in order to add value to system safety. The paper will examine the dominant theoretical perspectives on situation awareness and a model of this critical phenomenon is presented. The paper will show how the proposed model of situation awareness can be used as a framework for the analysis and identification of hazards relating to operator awareness in the context of system use. It is also suggested here that modelling situation awareness is useful in identifying areas of interface design where safety and usability are mutually exclusive. An illustration of the use of this technique is provided to show how the model can inform the design of interactive systems and how it can be used to generate evidence to support system safety claims.