Safety case development: a process to implement the safety three-layered framework

Safety cases are standard practice for capturing arguments and supporting evidence for why a given system is safe. However, current safety cases can be monolithic and for complex systems are often too verbose to be understood by a single individual. In addition, while they often contain well-structured and comprehensive arguments, these arguments are not supported by the evidence. To address these concerns and to make safety cases more streamlined and comprehensible a process has been devised to populate the Safety three-Layered Framework (SLF) concept. The SLF provides a modular safety case supported by engineering models and detailed analysis (such as formal methods). This paper illustrates the SLF with a simple example and demonstrates that the SLF can be successfully applied to give efficient and effective results.