ArRangeer: smARt RAilroad maintenance eNGinEERing with stochastic model checking

Funded by: STW / ProRail
Duration: November 2012 until May 2018


Summary of the project


Context. RAMS is often required by Dutch law or other government regulations for safety-critical systems like railroad infrastructure and signalling systems. Fault tree analysis (FTA) is a widely applied industry standard for RAMS analysis. It is frequently used and preferred by ProRail: ”complexe projecten: bij voorkeur foutenboomanalyse (FTA) of simulatiemodel” cf. "ProRail Leidraad voor RAMSHE -- LCM-studie", p. 40. FTA yields system availability and reliability, and can be used for critical path analysis. It can however not yet deal with a pressing aspect of railroad engineering: maintenance.

Problem statement. Fault trees (FTs) currently only support elementary maintenance aspects, e.g., the simple repair rates model that component’s faults are all repaired with the same speed. The ProRail context, however, demands for highly advanced maintenance models supporting condition-dependent strategies for preventive, corrective, clock- and age-based maintenance, inspection, monitoring, etc. In case of multiple failures, decision strategies need to specify which component(s) to repair first. In addition, maintenance costs are pivotal. FTA cannot yet cope with these advanced maintenance aspects.

Results. During this project, we have developed the framework of Fault Maintenance Trees, which is a formalism integrating maintenance into fault trees. Using this framework, we can analyse systems subject to a given maintenance policy for reliability, availability, expected number of failures over time, and expected cost over time. We can also break down these measures into different causes, such as failures caused by certain components or cost of maintenance vs. cost of failures. We have used this framework to analyse two case studies: The electrically insulated railway joint, and a pneumatic compressor for trains.

Tool. For the analysis of fault trees, the program DFTCalc is used and extended. Additionally, we are developing a tool that integrates many extensions of fault trees as well as attack trees, allowing conversion between different formalisms and analysis of combined trees.

Publications. A list of the publications written during this project can be found on our EPrints page.

Highlighted publications:

  • Overview of fault tree formalisms and analysis methods, summarzing over 150 articles on the state of the art of fault tree analysis.
  • Description of our Fault Maintenance Tree formalism. 
  • Case study of the electrically insulated railway joint (accepted for publication).
  • Case study of the pneumatic compressor (accepted for publication).

Partners. ProRail provides funding for this project. ProRail and Movares provide time, expertise, and data to assist the research, and to develop practical applications and case studies for the realized methods. This project is part of the ExploRail (same video in Dutch here) research program by ProRail, STW and NWO.

External team members. In addition to the employees listed below, this project is worked on by Prof. dr. ir. Leo van Dongen (Maintenance Engineering, University of Twente and NedTrain), Dr. Judi Romijn (Movares), and Ing. Martijn van Noort (ProRail).