Experts in Adamuz believe track leveling defect of 6.4 mm contributed to the fracture that caused the tragedy

A 6.4 millimeter track leveling defect, detected months earlier, may have been a key factor in the rail fracture that triggered the railway tragedy. Judicial experts believe this unevenness generated impacts that accelerated weld fatigue.

## The track 'pothole' and its domino effect

The judicial experts investigating the Adamuz railway accident have highlighted a crucial detail: a 6.4 millimeter leveling defect detected months earlier on the track, right at the point where the rail fractured. According to a report submitted to the judge, experts believe that dynamic loads caused by this irregularity may have accelerated the deterioration and subsequent fracture of the weld, leading to the tragedy. This defect, classified as Alert Level (AL) in October 2025, three months before the accident, could have had significant repercussions.

The way loads are transmitted between rails is fundamental here. The experts explain that certain trains, with bogies whose axles hold the wheels rigidly together, can generate a 'seesaw effect.' When a wheel falls into this 'pothole' on one track, the axle tilts, and as it recovers its horizontal position, the wheel on the opposite side may strike the other track. This constant interaction, amplified by axle rigidity and load transfer through sleepers, can cause accelerated fatigue damage to the material.

When questioned by the court regarding whether the evolution of this defect could have accelerated or even caused the fracture of the weld, the experts responded affirmatively: "Given all the consulted documentation, we could say yes." However, they introduce an important caveat: they do not know the specific evolution of the defect after October 2025, so they cannot determine if the anomaly continued to increase beyond regulatory limits.

## A renovated track and its surprises

The report also sheds light on another worrying aspect: the state of the infrastructure. The experts were consulted regarding the fact that a track, which had been renewed only months before, exhibited this type of defect during inspections. Their response is clear: "A priori," they consider this circumstance abnormal. This suggests that something went wrong in the renewal process or subsequent inspections.

The welds, as pointed out by the experts, are one of the weakest points in the railway structure. In this specific case, although the weld was within compliance, it was not optimal. The inspection report reflected a fullness of 0.14 millimeters, when the maximum limit for speeds exceeding 250 kilometers per hour is 0.15/0.20 millimeters. Despite the fact that the 114 welds installed in that section had been declared fit through testing in June 2025, the catastrophic failure less than a year later remains an enigma. The experts believe that several factors may have contributed to this event.

## Safety systems and 'canceled' risks

The investigation has also focused on the detection and safety systems installed in the section. In the documentation for Thales' new TIC technology, a specific risk was identified: that the TTC track circuit would fail to detect a rail fracture. This risk was classified as "catastrophic, occasional, and intolerable." Surprisingly, the same file indicated that detecting a rail fracture was not a requirement of the project, and subsequently, this danger appeared as "canceled" in the specific hazard registry.

When questioned by the court about whether it is normal to consider a risk mitigated simply by canceling it, the experts, while warning that they have not yet finished analyzing all the documentation, offer a significant response: "In general, it is not normal to consider a risk mitigated by canceling it." They add pointedly that "it should not have been canceled." This statement opens a new line of inquiry into risk management in railway infrastructure.

Finally, the experts have highlighted the importance of cars 1 to 5 of the IRYO train. Although they were not the ones that derailed, they consider them an "essential piece" for clarifying the causes of the accident. Therefore, they recommend extreme guarantees to prevent any alteration of evidence or relevant traces during their transport or review.