ABSTRACT
As stated in the foregoing section, a human performance related problem has been regarded as one of the radical determinants for the safety of any humaninvolved systems. It is natural that a great deal of work has been performed to unravel the human performance related problem. As a result, it was revealed that the use of procedures is one of the most effective countermeasures for the human performance related problem (AIChE 1994, IAEA 1985, O’Hara et al. 2000). In other words, procedures are very effective to help human operators in accomplishing the required tasks because they can use detailed instructions describing what is to be done and how to do it. However, the use of procedures has the nature of a double-edged knife. That is, since procedures strongly govern the physical behavior as well as the cognitive behavior of human operators, it is expected that the performance of human operators would be largely attributable to the complexity of procedures. Actually, existing literatures support this expectation, since the performance of humanoperators seems to be predictablewhen they use procedures (Stassen et al. 1990, Johannsen et al. 1994).
