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Last week, the Swedish Accident Investigation Authority published the final report on the extensive Iron Ore Line derailment in December 2023.

The derailment led to a two-month traffic stop on the railway line between Kiruna in Northern Sweden and Narvik in Northern Norway.

The Accident Investigation Authority's report shows that damage to a wheel caused the derailment.

Fracture

The direct cause of the derailment was that a wheel moved along its axle, the Investigation Authority finds.

The cause of the wheel moving was a fracture resulting from a fatigue crack in the flange, which is a protruded ridge meant to keep the wheels in place on the track.

This led to the wheel losing its press fit on the axle.

In its description of the sequence of events, the Accident Investigation Authority states that the derailed wheel, and later both wheels on the same axle, rolled with the train over a distance of 15 kilometers before several wagons eventually derailed and the train stopped.

The Accident Investigation Authority states that the wheel met applicable requirements and standards and that no deviations have been identified during the maintenance of the wheel axle.

Two derailments in a short amount of time

The December 2023 derailment caused extensive damage to rails, sleepers, and other infrastructure over a 15-kilometer distance.

The two-month stop in traffic also had consequences for the business sector in Northern Norway and Northern Sweden, not least for the mining company LKAB, which sends 10-12 iron ore trains daily in each direction between Narvik and Kiruna. The company reported a loss in revenue of about SEK 100 million per day during the stoppage.

"The Accident Investigation Authority's conclusions align with our analyses of what happened, and it's good that we can once and for all determine what caused the derailment. This type of damage is very unusual, and the sector systems along the track did not catch it either," said Linda Bjurholt, Area Manager for Logistics at LKAB, in a press release.

Bjurholt concurrently emphasized the vulnerability of the Iron Ore Line.

"The consequences of a disruption can be major, no matter the cause. This time, it was a damaged wheel; other times, there were other causes. We live with a one-track railway in an Arctic climate, where weather and wind can complicate repairs. The lack of capacity is a vulnerability for Sweden that must be addressed."

Another derailment took place in February 2024 with an unloaded iron ore train. The Swedish Accident Investigation Authority has already published the final report for this incident, which stated that hard-packed snow on the track and under the wagons was the direct cause of the derailment.

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