A modelling approach to railway track asset management

The UK railway network contains around 20,000 miles of track and is now carrying more, faster and heavier trains than previously. The effective management of this ageing and increasingly utilised system with limited financial resources is a significant challenge. Modelling tools are required to investigate the alternative strategies to manage such assets. The models available to date are very limited in their capability. A fundamental problem is their inability to adequately account for the underlying degradation process which is strongly dependent upon the history of the previous maintenance carried out. They also lack the complexity to enable the detailed maintenance and renewal options to be explored. This paper describes a modelling approach which first of all analyses the available data on the track geometry, and by implication the condition of the ballast, gathered at regular intervals by a measurement train. The analysis produces distributions of times for the track geometry to degrade to a specified state. Degradation distributions are therefore of relevance to the railway network under consideration, avoiding the need to use generic and possibly inappropriate data. With the degradation distributions available, a track section model is formed which incorporates the maintenance and renewal processes and provides a means of predicting the condition of the ballast section over time. The model uses a Petri net formulation with a Monte Carlo solution routine and enables the effectiveness of different maintenance strategies to be investigated. Ways in which the complexity of the model can be increased if desired is discussed and a case study is provided to indicate the use of the model.