Managing Human Error by Design

This book was written by Dr. David Embrey of Human Reliability Associates, with the assistance of the CCPS Human Reliability Subcommittee. Section 8.2, Managing Human Error by Design, which deals with the application of human factors principles in the process safety management system, was written by the Human Reliability Subcommittee. 

Even if a technical failure precedes the human action, the tendency is to put the blame on an inadequate response to the failure by an operator. Perrow claims that even in the best of industries, there is rampant attribution of accidents to operator error, to the neglect of errors by designers or managers [155], He dtes a U.S. Air Force study of aviation accidents demonstrating that the designation of human error (pilot error in this case) is a convenient classification for mishaps whose real cause is uncertain, complex, or embarrassing to the organization. 

Managers may wish to address human error by getting into the heads of their employees with training being the default corrective action— which will not be effective if error potential is designed into the work. 

Traditionally, the application of the term human error has been restricted to the operators and maintenance personnel at the sharp end, i.e. in immediate contact with the production system. There has also been a tendency to intermix the immediate cause of an accident (i.e. often a human error) with the responsibility for the occurrence, i.e. the person to blame. In a move away from such simplistic conclusions, there is now a trend to extend the analysis to include errors in the decision-making at all management levels of the company. Such analyses may reveal that human errors by operators, in their turn, are caused by poor equipment design, management s tacit acceptance of rule violations, inadequate work instructions and training, etc. It is usually possible to explain an action labelled as a human error fully by the circumstances in which it has occurred. 

At one time most accidents were said to be due to human error, and in a sense they all are. If someone—designer, manager, operator, or maintenance worker—had done something differently, the accident would not have occurred. However, to see how managers and supervisors can prevent them, we have to look more closely at what is meant by human error-. 

Human error Physical and cognitive actions by designers, operators, or managers that may contribute to or result in undesired events. 

When an accident report says that an accident was due to human error, the writer usually means an error by an operator or other front line worker. But designers and managers also make errors, not slips or lapses of attention as they usually have time to check their work, as well as mistakes or, less often, violations. 

Human errors may be accidentally performed by all personnel - designers, engineers, operators, and managers. Some theories attribute up to 90% of all accidents to human errors. 

The explosion of the nuclear reactor at Chernobyl (spelling changed recently to Chornobyl) in the Ukraine on April 26, 1986 sent radioactive material as far away as Sweden.90 The current death toll is 45. There has been a huge increase in childhood thyroid cancer, with cases as far as 500 km away 91 (U. S. bomb tests have also increased the incidence of thyroid cancers in the western United States.92) There is a 30-km exclusion zone around the plant where no one is allowed to live. This was created by the evacuation of 135,000 people 93 The accident is said to have happened because of combination of the physical characteristics of the reactor, the design of the control rods, human error and management shortcomings in the design, and implementation of the safety experiment. ... 

Virtually all incidents involve some sort of human error. Either a person initiated a train of events or failed to respond correctly as events started to go awry. Indeed, it is almost certain that some type of human error will be involved in incidents because usually the operator being, in Trevor Kletz phrase, the last man on the bus had an opportunity to stop the chain of events. If he or she fails to do so, this does not mean that he is to blame—after all there were probably many other mistakes made by supervisors, managers, engineers, and designers. 

Proposing that Prevention through Design be a specifically defined element in an Occupational Risk Management System is also influenced by ongoing transitions observed by this author in the methods to be used to eliminate or reduce human error. 

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