Predicting the performance of railway track is difficult owing to the complex and repeated nature of the loading, the many millions of cycles applied over the life of the structure, the need to characterise the often-infinitesimal rate of accumulation of plastic settlement, and the importance of differential settlements in the along-track direction, which can adversely impact train ride and passenger comfort. These come in addition to the usual soil mechanics challenges of reproducing in a constitutive model the real behaviour of soil and soil-like materials such as railway ballast. Degradation of the geomaterials comprising the trackbed and the underlying ground or earthwork owing to mechanical and environmental effects is a further concern. The paper discusses these issues and explores the application of fundamental soil mechanics principles and advanced constitutive models to understanding and quantifying their effects on railway track and trackbed performance. Recommendations for future research are made.