Rolling contact fatigue (squat) site trials at Carpenders Park and Cheddington (TM-MF-181)

In the mid-1970s rolling contact fatigue (RCF) defects in rails, colloquially called ‘squats’, began to appear in large numbers especially on the London Midland Region and Western Region. They were found to represent a derailment hazard due to the possibility of multiple fracture and difficulties in ultrasonic detection and assessment.