Is the safety index of modern safety integrity level(SIL) truly appropriate for the railway?

Abstract

Safety is paramount in rail transportation. The International Safety Standard IEC 61508, issued by the International Electrotechnical Commission (IEC) in 2000, describes the modern concept of safety and the specifications for safety evaluation in a systematic manner. On this basis, the EN 50129 railway transportation safety standard and safety integrity level(SIL) are established. Through the above analysis, the relationship between safety-related system reliability, acceptable risk, and safety index is summarized. It is clear that the safety index is based on acceptable risks. Nonetheless, as the economy and society advance, the safety index mandated by the SIL falls behind. Consequently, the principles and methodologies for calculating the safety index are presented. The paper proposes a reference for the Chinese railway safety index based on actual data from the Chinese railways over the past few years.