From the initial problem to the crash: The unknowns of the tragic accident in Toledo

MadridThe tragic train accident in Urda, in the province of Toledo, has resulted in dozens of injured and fatalities. Now, an investigation has been opened—it falls to the Civil and Instruction Section of the Court of First Instance of Orgaz (Toledo), in court number 2—which, taking into account the precedents of recent railway accidents, such as the Adamuz accident, is expected to be prolonged over time.

The progress of this investigation will have to resolve some unknowns that linger after the initial explanations about the disaster that have been given by the authorities, specifically by the Ministry of Transport. This Wednesday it explained in general terms the chronology of events.

Why does a system failure occur?

Everything begins with a failure of the computer system that controls high-speed rail in the State, the so-called LZB system, at 8:30 in the morning. There are 63 kilometers of track left without this system—it has been operating on the Madrid-Seville line since 1992—. The reason for the failure is a "computer malfunction," explained the Ministry of Transport, but for now, no further details are available. The same ministry said that it is "not frequent" for this system to fail, but acknowledges that it has happened on other occasions. In any case, when this happens, certain protocols are activated: to begin with, all affected trains are stopped.

What role does the Adif control room play?

With the LZB system down and the trains stopped, the Adif control center in Atocha comes into play, which is the one that takes control of the situation and, therefore, of the trains. It is the room technician who orders the drivers to start, or not, again. In this case, the order is given to resume normal movement for the six affected trains. In one of the cases, however, a driver notifies the control room that instead of applying normal movement, he wants to apply "sight" movement, taking into account that the LZB system is not working: according to the Railway Traffic Regulations, applying "sight" movement means traveling at a maximum of 40 km/h. The Adif control center operator agrees and allows it.

The same regulation establishes that it is possible to travel under these conditions in scenarios where railway safety is compromised or the automatic guidance systems have ceased to be reliable, which is what happens with the failure of the LZB system. In fact, this type of movement is prescribed when this system fails.

Why is the order given?

But for the rest of the trains, including the Renfe AVE involved in the accident (at 8:36 a.m.), the order given from control is to resume circulation normally, which surprises the Ministry of Transport. It is currently unknown at what speed the train was traveling at the moment the accident occurred, although in the affected section speeds can reach 250 km/h. Furthermore, in the case of the AVE that collided from behind with the Iryo, the order was given even though the Italian company's train was occupying its track. "Inexplicable," said minister Óscar Puente hours after the accident.

Why doesn't the Iryo train start?

Another question that the Ministry of Transport has not resolved—the information from the trains' black boxes still has to be extracted—is why the Iryo train remained stopped even though, in theory, it was also given the order to circulate, according to what the ministry explained.

Company sources have explained that the Iryo train driver stopped the train at 8:38 AM. At that moment, the driver began communications with the control center to "manage," as Iryo sources explain, "the resumption of the journey." This, however, did not happen. Other sources close to the company go further and assure Europa Press that the driver "was still in conversations" with the control center when the crash occurred, so its movement would not have been authorized. "We believe that the Iryo train receives the order that it can resume the journey, but we do not know why it does not do so," the minister said.

Why did no one foresee the crash for 15 minutes?

The journey covered by the Renfe AVE train from the moment normal service resumed until it rear-ended the Iryo train was 25 kilometers and approximately 15-17 minutes. During this time, according to the information that has emerged so far, no one gave a warning that there was an Iryo train stopped ahead on the same track where the Renfe train was traveling. And, therefore, no one told the AVE train driver to stop.