The Epidemiology of Squats and Related Defects

The development of squat defects has become a major concern in numerous railway systems throughout the world. The paper details the findings of extensive field Investigations Into squat and related rail defects within the RailCorp Infrastructure network covering the Sydney metropolitan and Interurban areas. Principally It catalogues the distribution patterns of where and when they arise (including where they do not occur) and how they grow. It also reviews the role of various potential rail surface initiators including slippage defects, rolling contact fatigue cracks and wheelburns. The paper describes the metallurgical research carried out to date and canvasses the various hypotheses regarding the principal causes of such defects. The paper also details the results of grinding squally rail and details measures proposed to reduce the potential for further squat development.