# A safety Lifecycle Example

EN 50126:1999 Railway Applications – The Specification and Demonstration Of Reliability, Availability, Maintainability And Safety (RAMS).

* Published by CENELEC – European Committee for Electrotechnical Standardisation.
* Provides Railway Authorities and the railway support industry with a process that enables the implementation of a consistent approach to the management of RAMS.
* Can be applied systematically throughout all phases of the lifecycle of a railway application.

Defines RAMS in terms of reliability, availability, maintainability, and safety and their interaction.

Defines a process for managing RAMS.

Enables conflicts between RAMS elements to be controlled and managed effectively.

Defines a systematic process for specifying requirements for RAMS and demonstrating that these requirements are achieved.

EN 50126 Lifecycle.

* Is a sequence of phases, each containing tasks, covering the life of a system from initial concept through to decommissioning and disposal.
* The lifecycle provides a structure for planning, managing, controlling, and monitoring aspects of a system, including RAMS.

<table><thead><tr><th width="205">Phase</th><th>Description</th></tr></thead><tbody><tr><td>Concept</td><td><ul><li><strong>Develop a level of understanding of the system</strong> sufficient to enable all subsequent RAMS tasks.</li><li>Review previously achieved safety performance</li></ul></td></tr><tr><td>System Definition and Application Conditions</td><td><ul><li>Define the mission profile of the system and its boundaries.</li><li>Establish the application conditions influencing the characteristics of the system.</li><li><strong>Define the scope of the hazard analysis.</strong></li><li>Establish the Safety Plan.</li></ul></td></tr><tr><td>Risk Analysis</td><td><ul><li><strong>Perform System Hazard &#x26; Safety Risk Analysis.</strong></li><li>Set up Hazard Log.</li></ul></td></tr><tr><td>System Requirements</td><td><ul><li><strong>Specify the overall System Safety requirements.</strong></li><li>Establishment of Safety Management</li></ul></td></tr><tr><td>Apportionment of System Requirements</td><td><ul><li>Define the RAMS acceptance criteria for the designated sub-systems and components.</li><li><strong>Apportion System Safety targets and requirements</strong> to designated sub-systems and components.</li></ul></td></tr><tr><td>Design and Implementation</td><td><ul><li><strong>Create</strong> sub-systems and components.</li><li><strong>Demonstrate that sub-systems and components conform to RAMS requirements.</strong></li><li>Implement a Safety Plan.</li><li>Prepare a Generic Safety Case.</li></ul></td></tr><tr><td>Manufacturing</td><td><ul><li>Implement a process that produces RAMS-validated sub-systems and components.</li><li>Use Hazard Log.</li></ul></td></tr><tr><td>Installation</td><td><ul><li>Assemble and install the total combination of sub-systems and components.</li><li>Initiate system support arrangements.</li><li>Establish Installation Programme.</li></ul></td></tr><tr><td>System Validation</td><td><ul><li><strong>Validate that the total combination of sub-systems, components, and external risk reduction measures comply with the RAMS requirements for the system.</strong></li><li>Commission the total combination of sub-systems, and components risk reduction measures.</li><li>Prepare, and if appropriate accept the Application Specific Safety Case.</li></ul></td></tr><tr><td>System Acceptance</td><td><ul><li>Assess compliance of the total combination of sub-systems and components with the overall RAMS requirements of the complete system.</li><li><strong>Accept the system for entry into service.</strong></li><li>Assess Application Specific Safety Cases.</li></ul></td></tr><tr><td>Operation and Maintenance</td><td><strong>Operate</strong> maintain and support the total combination of sub-systems and components such that compliance with system RAMS requirements is maintained.</td></tr><tr><td>Performance Monitoring</td><td><ul><li>Maintain confidence in the RAMS performance of the system.</li><li><strong>Collect, analyze, evaluate, and use performance and Safety statistics.</strong></li></ul></td></tr><tr><td>Modification and Retrofit</td><td><ul><li>Control system modification and retrofit tasks to maintain system RAMS requirements.</li><li><strong>Consider safety implications for modification and retrofit.</strong></li></ul></td></tr><tr><td>Decommissioning an Disposal</td><td><ul><li>Control system decommissioning and disposal tasks.</li><li>Perform hazard analysis and risk assessment.</li></ul></td></tr></tbody></table>

<figure><img src="/files/B7AgDibD1S5oqinB3I44" alt=""><figcaption></figcaption></figure>


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