A cracking inside the ring of the wheel was responsible. There was no indication of material or production failure. This crack was caused by excessive load and wear. When ICE began operations, there was no certification in place that would document appropriate design and reliability. Moreover no fracture mechanic calculation was done that could prove the strength of the wheel during its lifetime. According to the experts such wheels should not be operated at less than 880 mm diameter (new condition = 920 mm), subject to annual testing for inner and middle zone cracks. (An important NDT fact!) The diameter of the accident wheel was 862 mm. The limit set by Deutsche Bahn is 854 mm.
We interviewed District Attorney Jürgen Wigger, who explained that the wheel in question was first put into operation in 1994 and ran 1,8 Mill km until the accident in June 1998. In terms of assessing responsibility for the accident, it is significant that during its 4 years of operation, the wheel was never tested.