The machinist union requested the maximum speed to be lowered from 300 km/h to 250 km/h on multiple areas, the one where the accident happened being one of them. Both trains were driving under 210 km/h when the accident happened, so I don't think the "rattling" they reported was the issue.
As I mentioned before, this area was renovated last year, so attributing the accident to under-funding is highly unlikely. If the infrastructure happened to be the issue at the end, it might be because of different causes: eg. Planning the wrong materials for the amount of traffic / weather conditions / etc.
In general, when you talk about under-funding in the rail network it's often regional or small areas within the inter-city (larga distancia) and transport networks. High speed infrastructure is very well financed, it's not cheap to move trains close to 300 km/h.
Doesn't need to be underfunding, may 2025 was last summer and this was the first winter, defects in laying the tracks didn't have a chance to show up until now.
The biggest part then might be that they should have listened to the operators warnings and scheduled a proper re-inspection of the route once they started warning of issues.
> defects in laying the tracks didn't have a chance to show up until now.
Defects in laying the tracks have a chance to show up on an inspection, either the final one when building or one done at the regular intervals. If it doesn't shows up, your inspection is bad. If you can't inspect what you build, you can't build it.
Not going to be claiming to be an expert, but buckling is a well documented phenomenon and I'd be surprised if there wasn't possible issues due to contraction on the other end of the spectrum when it gets colder, the track was laid this last spring/summer so it's probably not been as cold for long before on the tracks.
Also modern high speed rails are built with continious welding without thermal expansion joints.
https://www.youtube.com/watch?v=zqmOSMAtadc goes through track building and the effects and literally mentions at about 12:30 that they do need to do inspections when it gets cold if the track cracks (there was a photo linked in another post about a cracked track).
Is it the cause? No idea but doesn't feel far fetched.
You seem very well informed, so I'm sure you've read that every single railway engineer and independent expert is saying that this seems like a freak accident and that the causes are totally unknown.
Knowing this, you're still all over the thread trying to score political points while there are dead people still on the tracks. One quick glance on your posting history is all one needs to see that you're happy to take any chance to do so, apparently including the death of at least 39 people. You disgust me. Y te creerás un "español de los buenos". Felicidades, patriota.
The collision was due to one train derailing first, if that was due to the track (as mentioned in andy12_'s toplevel comment) then listening to warnings could perhaps have avoided the accident.
Could have, though both trains were going slower than what the mechanic union asked for. Either or wasn't a factor, or the conditions were even worse than all parties believed.
Some have mentioned that the tracks were installed during may 2025, it's also the first winter so track issues and then thermal contraction could've cause too much strain.
Most recent reports indicate a broken weld on the track, so definitely possible damage from frost heave (is that a thing in the area it derailed?) or poor construction practices.
There is underfunding in all the railway network.
[1]: https://www.eldebate.com/economia/20250809/maquinistas-piden...