The S-A（State-Action） process chart can be adapted to the identification of hazards considering event occurrence order at the system level. However, it would be difficult to analyze basic failures such as component failure at the systemelement level, and this analysis of basic failures is indispensable for deriving measures to control risks due to the hazards. In order to address this issue, this paper firstly proposes how to construct S-A-FTs with priority-AND structures from the S-A process charts. Then, the proposed method is applied to the analysis of the failure mechanism of a redundant power-supply system. It is demonstrated that the S-A-FT provides a synergy effect which makes it possible to perform reasonable hazard/risk analysis, because combining the S-A process chart with FTA creates complementary roles to each other.

In the Investigation and Analysis Project for Safety Measures in Aging Production Equipment conducted by the Ministry of Health, Labor and Welfare from FY2017 to FY2019, two factors for risk of occupational accidents due to aging machinery, aging equipment and insufficient protection measures were pointed out, based on the data of about 500 workplaces. In this paper, using the data described in the report, I performed multivariate analysis on safety measures such as maintenance methods and inspection methods for aging machinery and equipment, and protection measures to prevent occupational accidents. As a result of analyzing the inspection points and inspection items of the aging equipment, high correlation between aging and the safety equipment or the function of the safety equipment was obtained. In addition, it became clear that there are aging machinery with safety measures problems, due to insufficient protection measures in terms of the latest level of safety equipment. I report the analysis results.

In Japan's manufacturing industry, the number of aging machinery that has been installed for more than 30 years is increasing. In this paper, I analyzed safety measures from the viewpoint of "insufficient protection measures" for occupational accidents caused by aging equipment, based on the results of the questionnaire response of the "Survey and Analysis Project for Safety Measures in Aging Production Equipment”^1）～3） conducted by the Ministry of Health, Labor and Welfare from FY2017 to FY2019, continuing from the previous report ^4）. As a result, it became clear that the most common occupational accidents caused by power machinery in the manufacturing industry, “drawn into a machine” accidents, are caused by inadequate protection measures of machinery and equipment. The "Guidelines for Comprehensive Machine Safety Standards"^5） provide "protective measures" at the design / manufacturing and use stages of machines, but I found many older machinery do not have sufficient measures in place. Focused and priority protection measures will be required for many older machinery.

STAMP/STPA is a safety analysis method that focuses on emergent accidents in large-scale complex systems that are difficult to predict by conventional safety analysis. However, the effectiveness of this method as a safety analysis method for unprecedented systems developed to create new markets has not been sufficiently demonstrated. In this study, we conducted a safety analysis using STAMP/STPA for a future unmanned vehicle system and evaluated the effectiveness of the safety analysis method. Based on the result of the analysis, it was confirmed that this safety analysis is effective for （1） systematic analysis, （2） clarification of inadequacies in the general specifications for safety design, and （3） clarification of issues related to the establishment of new rules for the practical use of systems that have no precedent for development.