DS/CLC/TR 50126-2:2007

Railway applications - The specification and demonstration of Reliability, Availability, Maintainability and Safety (RAMS) - Part 2: Guide to the application of EN 50126-1 for safety

1.1 This Technical Report provides guidance on specific issues, listed under 1.3 below, for applying the safety process requirements in EN 50126-1 to a railway system and for dealing with the safety activities during the different system life cycle phases. The guidance is applicable to all systems covered within the scope of EN 50126-1. It assumes that the users of the report are familiar with safety matters but need guidance on the application of EN 50126-1 for safety issues that are not or could not be addressed in the standard in detail. *1.2 EN 50126-1 is the top-level basic RAMS standard. This application guide, CLC/TR 50126-2 forms an informative part of EN 50126-1 dealing explicitly with safety aspects as limited by the scope defined in 1.3 below.*1.3 Limitation of scope *The scope is limited to providing guidance only for the following issues related to EN 50126-1. *i) Production of a top-level generic risk model for the railway system down to its major constituents (e.g., signalling, rolling stock, infrastructure, etc.) with definition of the constituents of the model and their interactions. *ii) Development of a checklist of common functional hazards within a conventional railway system *(including high speed lines, Light Rail Train.s, metro.s, etc.). *iii) Guidance on the application of the risk acceptance principles in EN 50126-1. *iv) Guidance on the application of functional safety in railway systems and qualitative assessment of *tolerable risk with examples. *v) Guidance for specifying relevant functional safety requirements and apportionment of safety targets to the requirements for sub-systems (e.g. for rolling stock: door systems, brake systems, etc.). *vi) Guidance on the application of safety integrity level concept, through all the life cycle phases of the system. *vii) Guidance on methods for combining probabilistic and deterministic means for safety demonstration. *viii) Guidance on the essentials (incl. maintenance, operation, etc.) for documented evidence or proof of safety (safety case) with proposals for a common structure for such documentation. *1.4 A diagrammatic representation of the scope and limitations of the scope cross linking with the safety activities within the life cycle phases of EN 50126-1 and the roles/responsibilities of the principal players is given in Table 1 below. However, for full comprehension it is suggested that these clauses are considered only after the whole document has been read: