Improving Human Reliability On Checking Toru Nakata Research Institute of Secure System, National Institute of Advanced Industrial Science and Technology (RISEC, AIST) Umezono 1-1-1, Tsukuba, Ibaraki, Japan. toru-nakata@aist.go.jp ABSTRACT Checks are fundamental operations to detect abnormalities and to ensure safety. Human reliability of checking is, however, insufficient to prevent issues being overlooked, resulting in many of the accidents that take place today. Even though people may attribute such instances of overlooking issues to a limitation in human attention, this paper concentrates on the reformation of checking procedures to improve reliability. The key concepts are: 1) ‘staticization’ of workflow, 2) independency triggering checks related to a job, and 3) objective questioning. These methods afford objectivity and stability of checking. The author states the mechanisms of these methods and then provides practical examples. Author Keywords Human Error; Check Methodology; Process Design; Staticization of Process. ACM Classification Keywords H.1.2 User/Machine Systems INTRODUCTION “It's a bad cook who can't lick his own fingers.” — Shakespeare, Romeo and Juliet. No accident can occur under proper scrutiny. Checks are therefore the most essential function for maintaining safety. The skill to detect errors could be said to be much more valuable than the skill associated with flawless job processing. Human workers often undertake responsibility for checking. Although we employ automatic machines to conduct checks that are free from human errors, we still have to instruct the machines correctly by manual operations. Human errors are crucial in both automatic and manual checks. Humans often make mistakes. According to the datasheet of human error probability complied by Gertman and Blackman [4], typical probabilities of general human errors are roughly estimated about 1% or so. In addition, performance becomes worse when the task becomes harder. People cannot complete their checks when the items being considered are numerous and when their layout is confusing. This means that human workers may no longer be equipped for undertaking checking tasks for the complex systems in modern industries. Gawande [3] emphasizes the importance of preparing and designing good checklists. He emphasizes the importance of a reduction in the number of checklist items. Gawande advises that checklists with more than ten items should not be used because of its complexity. For these reasons, we should change strategy and concentrate on the method of checking rather than on improving human ability. A shortage in human performance can be overcome if a checking procedure that is robust and easy to understand is in place. CONVENTIONAL STUDIES AND TECHNIQUES We should assume that human operators generally commit a significant number of mistakes. Countermeasures for the unreliability of humans have been researched and developed for many years. Effort and implementations for this purpose can be summarized as follows: Vulnerability of Human Checking There are two major mistake patterns when checking: 1) omission and 2) subjective judgment. 1) People often overlook the necessity of checking. We may also skip some items on the checklist by mistake. Omission is a serious error pattern since it eliminates checks and leaves the situation unmonitored and uncontrolled. Remembering mandatory checks is basically easy when we use tools such as memos, checklists, or reminder software. Nevertheless, many accidents due to omitting checks do occur because we often forget (or are reluctant) to use the reminder tools from the beginning of the process. 2) Even though we succeed in remembering to undertake checking, we may still ultimately fail by becoming subjective. Our thought process is not completely logical, and it is influenced by our experiences. For example, we can read the sentence below [12]: “I aulaclty uesdnatnrd waht I was rdanieg.” This phenomenon is called typoglycemia. Our cognitive process tends to find something meaningful in noise. In some cases, this tendency is harmful when conducting checking; we tend to assume that something which is nearly correct is in fact perfectly correct. Having prejudice that the situation is all right, we may overlook mistakes and fail to submit accurate reports. For efficient and effective checking, we therefore have to eliminate subjectivity from our consciousness. Types of Human Error and Difficulty of Detection Several conventional explanations exist concerning how people detect their mistakes. The probability of error