Below we review what is known about what happened in the 23 minutes that elapsed from when the main safety system failed until the collision between both trains led to one of the most serious railway accidents in the history of Spain.
For a high-speed train to collide with another, a concatenation of failures had to occur, as inferred from the initial explanations given by the Minister of Transport and Sustainable Mobility, Óscar Puente. The first failure was that the LZB system regulating traffic fell. Another was that the Adif Control Center allowed the AVE driver to resume normal speed. A third was that the Iryo train could not move and that no one realized the AVE was heading towards it at full speed. The Independent Authority for Technical Investigations of Accidents (AITAT) emphasizes that "all hypotheses" regarding the causes of the accident "are open" in the first informative note published on Thursday.
How do the automatic safety systems of high-speed trains work on the line connecting Madrid with Seville? The main system on that stretch is the LZB, or Continuous Supervision Railway Traffic Control System, which is based on constant communication between each train and the cables laid along the track. In this way, it controls the speed at all times to be able to stop if it is going faster than allowed and there is a risk of collision.
In case of LZB failure, the trains in operation stop and switch to protocol BSL (Lateral Signal Blocking), which involves the operation of trains according to the signals located along the track. As a backup, the safety system known as ASFA (Signal Announcement and Automatic Braking) comes into play. When the train passes over a series of devices deployed at certain points on the track, it receives information about whether there are red signals in the next kilometers that require stopping. But these warnings do not indicate whether there is another train ahead.
The ASFA system can automatically activate the emergency brake in front of a red signal, but "what the regulation states is that the driver can pass it if they have regulatory authorization. Like the one that the AVE received from Atocha," explains civil engineer and judicial expert Fernando Minaya.
The accident raises numerous questions about the chain of circumstances that led to the tragedy and about the safety systems of Spanish high-speed trains.
The first is why there was an initial failure of the automatic LZB system near the Urda station, which the Minister of Transport, Óscar Puente, attributed to a "computer communication failure." Puente indicated that this type of failure "does not happen every day, but it does happen."
Another mystery is to know the reason why the Atocha control center ordered the driver of the AVE 2080 to resume circulation at "normal speed"—that is, above 100 kilometers per hour on that stretch—when the Iryo train was stopped about twenty kilometers away, instead of ordering it to go at "sight speed."
"It is a key error. I believe there is evidently a human error, but it is not so much about blaming a person, but understanding that there are protocols and systems that help prevent someone from making a mistake and that the safety of a railway line depends on an individual's conditions," states José María Goicolea, professor at the School of Civil Engineers of the Polytechnic University of Madrid.
Another question to resolve is why the ASFA system did not stop the AVE: was it due to an action by the driver, executed upon receiving authorization to resume? Was it another technical fault? Or why was the Iryo train unable to restart and remained stopped at the Urda station? Were they aware at the Control Center that the train was stopped on the track? What happened in the minutes from when the Iryo gave the alert to when it was struck by the AVE? These are just some of the questions that the ongoing investigation will need to address.
The data on safety systems comes from the Railway Circulation Regulations, approved in Royal Decree 664/2015 of July 17. It also includes information from COI No. 01/25 of Adif, which establishes a series of complementary prescriptions to those included in the regulation for the authorization of passing signals that order a stop.
An article written by Paula Guisado (RTVE), initially published on 30 October 2026, 08:10 (CET)