Reliability, availability and maintainability modelling - metrics and models

The drive for improved railway performance is a fundamental commitment of both UK Government and the railway industry. However, the experience of the last few years highlights the complexity of assessing railway technical performance in a dynamic arena where analysis forecasts carry a significant margin of uncertainty. Building upon the "Performance by Design" overview presented by Brian Halliday at the recent IEE On The Right Lines Seminar of May 2004, this presentation outlines some of the issues pertinent to the assessment of reliability, availability and maintainability within the UK railway environment. If the range of reliability and performance metrics used at route, system or asset level are considered, then it is evident that somewhere in the hierarchy a change in measurement currency has occurred. It is at these interfaces where systems reliability modelling can provide the translation between metrics and thus enable the derivation of meaningful/traceable performance related system requirements. It is suggested that it is only through the establishment of suitable reliability models to assess target, predicted and actual performance that reliability growth principles can be identified, developed and ultimately managed into service.