Special Issue on prognostics and health monitoring in railways

In recent years, the application of Prognostics and Health Monitoring (PHM) techniques to railway systems has attracted increased interest in terms of both research and industrial application. A number of drivers have triggered this process: it is worth mentioning here the stringent requirements posed on both the rolling stock and the infrastructure in terms of their reliability, availability, maintainability and safety, which have been further exacerbated by the separation of the infrastructure mangers from the operators and by interoperability requirements. Furthermore, PHM is nowadays seen as a major tool to reduce maintenance costs for railway assets, through the implementation of condition-based maintenance. As a consequence, electronics and software are increasingly forming an essential element of modern railway vehicle technology, and the monitoring of components such as the train control and communication system, doors, etc., is now extensively available on the recent generations of trains. On the infrastructure side, continuous monitoring is already available for some critical elements such as bridges, switches and electrical substations, whilst advanced techniques for the continuous monitoring of the condition of the track and of the overhead line are rapidly evolving from the subject of theoretical research to in-field applications. The purpose of this special issue is to present a diverse set of applications of PHM to railway systems, in order to summarise the current status of research in the field and to highlight present challenges with the development and take-up of these technologies. The special issue consists of six papers, all of which have been peer reviewed by independent reviewers. The issue begins with paper ‘‘Maintenance of bogie components through vibration inspection with intelligent wireless sensors: A case study on axle-boxes and wheel-sets using the empirical mode decomposition technique’’ by Trilla and Gratacos, which presents the development of a network of wireless sensors for the condition monitoring of railway bogies through the measurement of axle-box vibrations. The second paper is ‘‘Alarm handling for health monitoring: Operator strategies used in an electrical control room of a rail network’’, by Dadashi, Wilson, Golightly and Sharples, which develops methods for alarm management in the setting of rail electrical control. The issue continues with ‘‘Monitoring of strain of in-service railway switch rails through field experimentation’’ by Cornish, Smith and Dear, reporting on the findings of field experiments to monitor the in-service loads of switch panels, with the final aim of improving the understanding of the causes for deterioration of these components in service. Continuing with the topic of health monitoring of switches, the paper ‘‘A novel approach to diagnostic and prognostic evaluations applied to railways: A real case study’’ by Pliego Marugán and Garcı́a Márquez discusses the condition monitoring and predictive maintenance of the point mechanisms. The fifth paper, ‘‘Measuring and monitoring operational availability of rail infrastructure’’ by Stenström, Parida and Kumar, investigates the issue of availability in the operation and maintenance of railway infrastructure. Different definitions of availability are introduced, and their correlation to train delays is examined based on a case study from Sweden. The last paper, ‘‘Context-driven decisions for railway maintenance’’ by Villarejo, Johansson, Galar, Sandborn and Kumar, outlines an approach to the prognostics and maintenance decision for the railway infrastructure, emphasising the use of hybrid models and data aggregation for the reliable estimation of the Remaining Useful Life of the railway track. We believe these six papers together provide a useful picture of the present status of research in the field, and we hope that readers will find in this special issue inspiration to identify new challenges for their future research work. As a final note, we would like to thank all of the authors for their contributions to this special issue, and the reviewers for their insights and recommendations that greatly helped the authors to enhance their contributions. Finally, we would like to thank the Editor of the Journal of Rail and Rapid Transit, Professor Simon Iwnicki, and the journal’s editorial team for their commitment on the publication of this special issue.