Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing, UT

The need for a better inspection method became a high priority because of a
derailment at Manchester, NY in 1911, in which 29 people were killed and 60
were seriously injured. In the U.S. Bureau of Safety's (now the National
Transportation Safety Board) investigation of the accident, a broken rail was
determined to be the cause of the derailment. The bureau established that the
rail failure was caused by a defect that was entirely internal and probably
could not have been detected by visual means. The defect was called a
transverse fissure (example shown on the bottom). The railroads began
investigating the prevalence of this defect and found transverse fissures were
widespread.