ABSTRACT
This chapter introduces the notion of constraints which are factors that limit or restrict the ability to act. Understanding workplace activity requires an understanding of the constraints that guide and limit performance. Jens Rasmussen, a Danish electrical engineer, pioneered the study of constraints on human performance. Some constraints come from the nature of human cognition whereas others come from the environment within which work takes place. Rasmussen developed a number of tools and techniques, such as the abstraction hierarchy, for probing and analysing these constraints. Making constraints easily visible to the human operator is the aim of ecological interface design (EID) as described earlier. More recently, Rasmussen developed techniques for thinking about large-scale problems of risk management. One powerful concept is that of the ‘safety space’ bounded by economic and working constraints. These ideas are illustrated by the events surrounding a UK rail disaster at Clapham Junction and by the outbreak of BSE (‘mad cow disease’). Examples of human adaptability to workplace constraints are provided by the healthcare industry.
