This part 1 of EN 50126-considers RAMS, understood as reliability, availability, maintainability and safety and their interaction;-considers the generic aspects of the RAMS life cycle. The guidance in this part can still be used in the application of specific standards;-defines:-a process, based on the system life cycle and tasks within it, for managing RAMS;-a systematic process, tailorable to the type and size of the system under consideration, for specifying requirements for RAMS and demonstrating that these requirements are achieved;-addresses railway specifics;-enables conflicts between RAMS elements to be controlled and managed effectively;-does not define:-RAMS targets, quantities, requirements or solutions for specific railway applications;-rules or processes pertaining to the certification of railway products against the requirements of this standard;-an approval process for the railway stakeholders.This part 1 of EN 50126 is applicable to railway application fields, namely Command, Control and Signalling, Rolling Stock and Fixed Installations, and specifically:-to the specification and demonstration of RAMS for all railway applications and at all levels of such an application, as appropriate, from complete railway systems to major systems and to individual and combined subsystems and components within these major systems, including those containing software; in particular:-to new systems;-to new systems integrated into existing systems already accepted, but only to the extent and insofar as the new system with the new functionality is being integrated. It is otherwise not applicable to any unmodified aspects of the existing system;-as far as reasonably practicable, to modifications and extensions of existing systems already accepted, but only to the extent and insofar as existing systems are being modified. It is otherwise not applicable to any unmodified aspect of the existing system;-at all relevant phases of the life cycle of an application;-for use by railway duty holders and the railway suppliers.It is not required to apply this standard to existing systems which remain unmodified, including those systems already compliant with any former version of EN 50126.The process defined by this European Standard assumes that railway duty holders and railway suppliers have business-level policies addressing Quality, Performance and Safety. The approach defined in this standard is consistent with the application of quality management requirements contained within EN ISO 9001.