Human Factors and Their Optimization

Weak control of human factors leads directly to error. An error can result in an initiating event of an accident sequence (directly by the mistake made or indirectly such as by a process control loop failing prematurely). Human error also is the cause of failure of each layer of protection. This paper discusses each of the 10 primary human factors and describes what we know about their relative importance in accident causation. The data presented is from basic research (previous research by others, and also by the authors) and review of the root causes of more than 1000 accidents and near misses. The paper lists where focus should be placed (i.e., which human factors tend to be key) and provides proven ways to optimize these human factors so that the base human error rate at a site is as low as possible. Tie-in to other applications, such as determining the probability of human error for risk analysis is also presented. Case studies and examples are used throughout the paper to illustrate key points.