20 seconds. That is the time that, according to Álvaro Fernández Heredia, has passed since the derailment of the Iryo train in Adamuz and the arrival of the Alvia train in the opposite direction. “It still cannot be concluded that the Alvia collided with the Iryo cars or with any element of the road,” said the president, who, remembers, will take days to reach conclusions.
It puts the focus, however, on the LZB security system.
What has happened? What we know, at the time we write these lines, is that an Iryo train and an Alvia have had an accident at the same point on the Andalusian high-speed corridor. Until now, the first assessments have suggested that the Italian train derailed in the middle of the straight line and the Renfe train collided with it. However, this “cannot yet be concluded,” according to Álvaro Fernandez Heredia in statements to Chain Being.
What is certain is that both trains have areas that are very difficult to access, with serious damage to their structure. The Alvia train also fell down a four-meter embankment. There are, at the time we write, 39 deaths (including the 27-year-old Renfe driver) and it is not ruled out that more bodies will be found once the rescue work is completed.
20 seconds. It is, according to Fernández Heredia, the time that has passed since the Iryo train derailed and the Renfe train arrived at the same place. However, Heredia has made it clear that understanding what happened at that moment is, for the moment, conjecture because the investigation that the Railway Accident Investigation Commission (CIAF), who They already did the same in Angrois, in the Galician accident of 2013.
Explained visually in The CountryWhat we do know is that the Iryo derailed first when it was traveling at 210 km/h in a space limited to 250 km/h, so excessive speed seems to be ruled out. After 20 seconds, the accident worsened with the arrival of the Alvia, which did so at 205 km/h (also below the maximum speed allowed). Both trains were found at a distance of 700 meters between them, with the Alvia falling on the embankment located next to the tracks.
Those 20 seconds, everything indicates, will be key to the investigation. And the president of Renfe pointed out on the radio that “the LZB system is equipped in such a way that when there is an obstacle on the track, the path is blocked and prevents circulation and orders emergency braking to the train. But apparently, the time interval between one train and another that crossed in opposite directions has been 20 seconds and, therefore, it is impossible for this mechanism to act.”
What is the LZB? The LZB is the security system used in the Andalusian corridoron the Alvia Madrid-Toledo and on Cercanías lines C-5 in Madrid and the entire Euskotren network. The acronym refers to the German word Linienzugbeeinflussungsince the system is also used in Germany and Austria.
The system consists of a cable that extends along the track, centered but drawing a slight zigzag. This wiring sends train running informationthe maximum speed of the road and the distance remaining before reaching a new speed limit change. If the driver does not reduce the speed, it is the train that activates the emergency braking.
This wiring sends electrical signals in a closed circuit to recalculate the aforementioned variables through beacons. When the track is blocked, the transmission is interrupted and the system automatically orders the train to stop. However, according to the president of Renfe, the 20 seconds that have passed between the derailment of the Iryo train and the arrival of the Alvia have not been enough to stop the vehicle. It remains to be seen whether he braked previously and lost speed or not.
Dated. The LZB system is considered an outdated safety system and Spain is one of the few countries in Europe that continues to use it on a high-speed railway section. In fact, by European order to facilitate interoperability, The LZB system in the Andalusian corridor is being replaced by ERTMS 2the European system that is already mandatory on all trains.
ERTMS 2. This system It is a simplification of the processboth in equipment and operation. The data connection is made through GSM-R so the beacons only serve as a redundant system to locate the train.
In exchange, radio equipment is used that communicates the train with the Movement Authority or MA (Movement Authority), explain in How trains work. This MA is responsible for telling the driver the maximum speed at which they can travel and for how many kilometers, but it includes a greater amount of information such as temporary speed restrictions, which makes it easier to comply with the limits.
The system has the advantage that if a train suffers a problem but can no longer stop, it can pass through an enclave at an appropriate speed without the risk of derailing and only applies emergency braking when the situation is safe. On the contrary, it closes the passage of all trains instantly so that a collision does not occur. The system is considered more secure because it has more information, redundant systems and decisions are made more quickly.
Speed is key. Having a system capable of more closely monitoring the status of the trains and managing traffic is key when we travel on a high-speed train. We must keep in mind that when we travel at 205 km/h we are traveling 56.94 m/s. That is, in the 20 key seconds indicated in the Adamuz accident, 1,138 meters were covered.
It must also be taken into account that the braking space increases exponentially with an increase in speed. At the same time, braking space is drastically reduced at lower speeds and the violence of an impact or a derailment is less.
Photo | Wikimedia 1 and 2
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