Modelling Rail track maintenance planning using simulation

In Australian rail freight operations, railway track maintenance costs comprise between 25-35 percent of total train operating costs. This paper describes a model which has been developed to deal with the track maintenance planning function at the medium to long-term levels. This model provides a simulation of the costs and benefits of degrading railway track conditions and by the maintenance work that may be conducted. The model simulates the degrading track condition using an existing track condition model. Track condition data from that model is used to determine if safety related speed restrictions are needed and what immediate maintenance work may be required for safe train operations. The model, which is currently implemented using a series of linked EXCEL spreadsheets, can deal with up to nine adjacent track segments with differing physical characteristics. Operating costs for up to five different train types are calculated from simulated train delays and maintenance work. The latter is a function of the level of track maintenance intervention specified by the user. The model outputs the net present value of the financial benefits of undertaking a given maintenance strategy, when compared with a base-case maintenance scenario. The model is also capable of calculating the costs of track maintenance and train operations when traffic or track conditions are changed. This capability can provide the user with an insight into various what if scenarios. In particular, the track engineer can assess the possible benefits in reduced operating costs from upgrading track infrastructure or the impacts of changed traffic. After describing the model inputs and the assumptions used, the paper deals with simulation of track maintenance and of train operating costs over time. The results of applying the model to a test track section using a number of different maintenance strategies are also given.