Its up to 68 deaths now actually. I never had issues with spanish trains, but it seems they are having some major problems recently. If i can immediately remember the last mass casuality train accident off the top of my head then its happening too often. The last one wasnt even a year ago. 46 deaths that time. Like wtf are you doing with your train systems for it to fuck up this badly twice in one year???

https://en.wikipedia.org/wiki/2026_Adamuz_rail_disaster

Apparently bad rail welding and wrongly configured automatic rail fault detection thresholds in that case. For this new one it will take a while to know for sure i guess but it looks like human error during the signalling.

There the accident was caused by illogical placement of different train protection areas. The fast section had a modern high-speed train protection system and where there was a curve, and therefore a slower section, the track was protected by the older Spanish train protection system.

The last piece of information from the high-speed system should of course be "curve ahead, slow down", but because the crew installing it was looking only at the map of the high-speed section, they failed to notice that where the section ends, there is something immediately beyond. For them it was a straight stretch of railway that then continues "wherever" beyond the "relevant section".

There was a physical trackside sign warning about the curve, but good luck spotting a trackside sign at a speed of 250 km/h, especially when the in-cab device telling you what speed to drive says "250 km/h until further notice by the in-cab device".

Of course, where the high-speed section ends and the older section begins, there is a train protection transmission saying "in a couple hundred metres the maximum speed is 80 km/h", but at point there's nothing left to do except slow the train down to decrease the magnitude of the disaster.