I haven’t looked it up but I would bet you it’s due to fatigue limits. They probably use aluminum a lot which always fatigues no matter how light the stress (a bit like me tbh…) so anything made from aluminum gets retired after a set time period.
The same is true for jets. Each flight expands and contracts the airframe since it’s a pressure vessel, and the wings can deflect a large amount too.
The actual train is >30 years old, it was only painted like that 8 years ago. (Probably repainted a couple of times too lol)
I haven’t looked it up but I would bet you it’s due to fatigue limits. They probably use aluminum a lot which always fatigues no matter how light the stress (a bit like me tbh…) so anything made from aluminum gets retired after a set time period.
The same is true for jets. Each flight expands and contracts the airframe since it’s a pressure vessel, and the wings can deflect a large amount too.