IEC 61508 and ISO 26262 - A Comparison Study

In the process of realizing safety critical systems, guaranteeing functional safety is always mandatory. However, multiple factors are challenging functional safety: (i) the complexity of new electrical and electronic architecture leading to different malfunctioning behavior. This malfunctioning behavior can lead to unwanted hazards and then to unreasonable risk, (ii) the availability of various functional safety standards and (iii) high expenses. If functional safety standards are used in the design of a safety critical system, it is important to evaluate the risk accurately. The risk is related to the probability of failure. In this paper, a comparison between two functional safety standards ISO 26262 and IEC 61508 is presented. These standards are used in the automotive field and in the industrial automation field, respectively. Additionally, a limitation in using IEC 61508 to verify ISO 26262 is emphasized. Focus is the safety lifecycle and the failure rate evaluation methods, which are applied by the two standards. The comparison made in this paper represents the opinion of the authors based on their experience and is not intended to be absolute.