# Madrid-Seville train collision: safety failures under investigation - Original post: https://www.twitter.com/i/status/2115823153817542994 - Source account: [@Bleispit](https://x.com/Bleispit) - Source language: Spanish - Target language: English - Duration: 2:55 - Published: 2026-10-29 - Machine translated. Check the original before quoting. - Canonical URL: https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation - Original-language version: https://www.translate.mom/transcript/wuRCa06JYdA7/es/choque-de-trenes-en-la-l%C3%ADnea-madrid-sevilla-fallos-de-seguridad-investigados.md ## Transcript [0:00](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation) How can one train catch up with another on a high- speed line? [0:04](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=4) To understand it, we need to look at the safety chain that should have prevented it. [0:09](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=9) The track is divided into sections several kilometers long, called blocks. [0:13](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=13) The rule is simple: in each block, only one train. [0:19](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=19) Electrical circuits in the rails detect whether the block is occupied. If it is, the train behind cannot enter. [0:28](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=28) On the Madrid- Seville line, this is monitored by a system called LZB. It communicates with the train constantly via a cable laid between the rails. [0:36](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=36) It knows which blocks are occupied, so it calculates how far each train can go and at what speed. The driver sees it on the screen. [0:47](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=47) And if there is a train ahead, the LZB sets a stopping point before reaching it. [0:52](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=52) If the driver does not brake in time, the system brakes the train itself, automatically. [0:58](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=58) But today, at 8:32 a.m., the LZB control center in the area has failed. [1:04](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=64) Six trains have come to a standstill over 90 kilometers. [1:07](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=67) When the LZB fails, plan B kicks in: trackside signals and a system called digital ASFA. [1:15](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=75) Beacons on the ground check that the train obeys every signal. [1:19](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=79) If it passes a red one without permission, it brakes it. And here is the key. A signal at red can be passed if the control center authorizes it. [1:29](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=89) It is called authorized passing. And in that mode, the ASFA only monitors speed. [1:34](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=94) It does not know whether there is a train ahead. [1:37](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=97) That is why the rules require on- sight operation. [1:40](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=100) Slowly, at around 40 kilometers per hour, so you can stop for anything you see. [1:46](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=106) The main hypothesis, according to the Transport Ministry, is that Atocha control center authorized it to proceed with the Iryo still stopped ahead. [1:57](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=117) The minister has called it an inexplicable error, but an order from Atocha is not enough for this to happen. [2:03](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=123) Even if control authorizes it to proceed, the backup safeguards are still there. [2:07](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=127) Proceeding on sight requires going slowly. [2:10](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=130) And ASFA, when passing a signal at danger with authorization, monitors that speed. [2:15](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=135) If the train exceeds it, it should brake it. [2:18](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=138) What is still unknown is why that order was given, what the driver saw, and why none of those safeguards stopped the train. [2:26](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=146) That is now being investigated by the Railway Accident Investigation Commission. [2:31](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=151) A system like this has several layers, so that a single failure is not enough. Today, for reasons that still need to be clarified, Several failed at once. Our thoughts are with the victims and their families. [2:44](https://www.translate.mom/transcript/wuRCa06JYdA7/en/madrid-seville-train-collision-safety-failures-under-investigation?t=164) Very soon, the full and more detailed version in a long-form video.