Exploring the role and content of the Safety Case

It is a requirement to provide a safety case for all of the Major Accident Hazard (MAH) industries. The prime purpose of the safety case is for the Dutyholder to demonstrate to the Regulator there are effective means for ensuring safe operation in accordance with a goal setting safety regulation regime. This paper will take forward ideas presented in Expert Advice to the Ladbroke Grove Rail Inquiry Part 2 (6) in regard to the principles of a safety regulation regime and the role and content of the safety case. Currently, with local variations within different major hazard sectors, it is common for a Safety Case (SC) to describe an organisation's technical systems and processes and its Safety Management System (SMS). These sections are accompanied by a risk assessment which attempts to demonstrate that through these measures and perhaps further identified control measures, risk has been reduced to As Low As Reasonably Practical (ALARP). This paper criticises the current norm, accusing it of producing unbalanced documents that fail to present a complete and strong argument for why the organisation's arrangement lead to continuing safe operation. The completeness and strength of an argument can be rated by comparison to theories and models of argument construction e.g. Toulmin et al 1979((39)). The strength of an argument is limited by the quality of knowledge and science used as the basis. In the field of safety the quality of science varies depending oil the context, for example more confidence can be placed in the understanding of the science of materials and structures than in the understanding of organisational behaviour. Consequently, in general, the conditions under which hardware components and structures fail can be forecast with greater certainty than the performance of a team of people tackling a complex problem. The benefit of using formal argument structures is that constituent parts of an argument are made explicit, increasing the visibility of incomplete and weak arguments. Validation of the Safety Case would entail appraisal of the constituents of the argument. This paper explores the application of an argument model, commenting on the viability and benefit of its adoption. This paper also considers the degree to which the proposed approach is implemented in other fields such as insurance, aerospace and defence.