A stochastic railway track maintenance model

Railway track geometry quality degrades as the track is used and hence maintenance is required to keep the track quality within acceptable limits. Railway maintenance managers must plan the inspection, maintenance and renewal of the track so that the track condition remains in a good state and that costs are effectively controlled. When the track quality deteriorates it can be restored to a good condition by using a tamping machine to readjust the ballast below the sleepers. The tamping machine works by lifting the track to the required level, inserting tines at either side of the sleepers and squeezing the ballast beneath them so that the track remains in position once released. As well as restoring the track geometry, tamping also results in some deterioration of the ballast and this leads to increased deterioration rates following successive interventions. In this paper a Petri net model of a single 1/8th mile track section is presented and analysed using a Monte Carlo simulation approach. The model accounts for the deterioration, inspection, maintenance and renewal of the track section and also considers the damaging effects of tamping on the ballast. The model can be used to assess the effects of a maintenance and inspection strategy on the track performance and is demonstrated on an example track section.