Squats on the Great Britain rail network: Possible root causes and research recommendations

Rail squats are a type of isolated railhead fatigue defect that costs Network Rail millions of pounds every year. Despite significant research into the topic there is still a lack of detailed understanding on how squats are initiated and propagated or the best methods to maintain track in order to manage squat defects.

This paper presents a correlation analysis examining which track characteristics might be associated with the initiation and development of squats defects on the Great Britain (GB) railway network. Data was analysed for 4,265 squats from three routes (two Intercity routes and one Suburban route) using records of squat for a seven year period between 2011 and 2017.

The correlation analysis show that different route characteristics (such as track geometry, type/number of vehicles and traction and braking cycles and maintenance activities) would have an important influence on the probability of squats defects.

The results suggest that rail grinding is an important method to control the development of squats. There is some evidence, based on limited data from the suburban route, that squats rates could be reduced by 85-90% if the combined wear from traffic and grinding exceeds 0.2 mm/year.