Material fatigue in Västtrafik's tram fleet – a rail safety challenge
Author: Andreas Ellhar
Apr 11, 2025DEKRA and Västtrafik – extending the service life of Gothenburg's tram fleet.
Västtrafik AB is the regional public transport authority owned by the Västra Götaland Regional Council. Its fleet of M32 trams in Gothenburg has been in operation for nearly 20 years, with each vehicle covering an average of approximately 60,000 kilometres annually.
During routine maintenance, cracks were discovered in the upper corner of the door openings. Further inspections revealed that the same type of cracking was present on many vehicles. A subsequent investigation identified material fatigue as the root cause, raising concerns about the structural integrity of the fleet, continued operation and future maintenance costs.
Technical analysis and structural reinforcement
DEKRA was commissioned to carry out a comprehensive technical investigation. Through systematic analysis of vehicle measurement data, track data and operational stress levels, DEKRA identified cyclic torsion as the primary cause of the damage.
After determining the root cause, DEKRA developed a comprehensive mitigation programme that included:
- Structural redesign of the fatigue-prone door corners.
- Optimised repair methods.
- A targeted programme of periodic inspections.
With cyclic torsion identified as the governing load case, the original fatigue life of the affected area was calculated to be less than 50,000 kilometres, explaining the observed crack formation. By implementing the repair programme together with targeted inspection intervals, the vehicles can remain in safe operation for several million kilometres, providing greater predictability and significant long-term cost savings for Västtrafik.
The result: lower costs and enhanced safety
DEKRA's analysis and corrective measures enabled Västtrafik to:
- Significantly reduce the risk of unexpected service interruptions.
- Lower future repair and maintenance costs.
- Ensure a safer and more sustainable tram fleet.
Magnus Dahlberg, Head of BU Engineering Asset Management, DEKRA Industrial:
"When it comes to material degradation, it is virtually impossible to protect yourself through contractual warranties alone. The key is to ensure from the very beginning that vehicles are designed, procured and verified for a long service life."
Lessons learned and future requirements
Material degradation leads to operational disruptions, increased costs and reduced service life. Within the rail vehicle sector, both regulatory requirements and commercial incentives for managing these risks remain relatively limited.
The experience gained from the M32 tram fleet highlights the importance of all parties involved in procurement taking active responsibility for vehicle longevity. Verifying the expected service life from the outset is essential. DEKRA's ambition is to continue promoting best practices and improved industry processes, with a strong focus on lifecycle integrity, continuous verification and long-term predictability.
Looking to prevent costly material fatigue in your rail fleet?
Contact DEKRA to learn how our engineering specialists can help you analyse material fatigue, extend asset life and develop tailored solutions for your rail vehicles.