The Madrid-Seville high-speed railway line, where the collision between two trains occurred this Wednesday, has different signaling and protection systems designed to regulate circulation, control the distance between trains and reduce the risk of accidents. The first hypotheses point to “human error by an Adif operator in the event of a breakdown in the main signaling system,” according to Executive sources.
The crash took place at kilometer point 118, between the towns of Mora and Orgaz and Urda (Toledo), on the oldest high-speed line in Spain (inaugurated in April 1992, coinciding with the Universal Exhibition in Seville that year). The infrastructure has the German LZB system (Linien Zug Beeinflussung), a railway protection technology that continuously monitors the speed of the trains and transmits traffic indications to the driver's cabin, according to the Adif Network Declaration, the document that includes the characteristics of the infrastructure and the access conditions for railway companies. However, when the automated security system fails, control becomes manual.
The first information indicates that this security system failed early this Wednesday, which has caused eight trains to stop in the area. Afterwards, the control center, in manual mode, ordered all trains to resume moving. But an Iryo convoy failed to start and stopped. Due to the order of the controller at the Atocha center, an AVE that was behind him resumed its path and, shortly after, collided with the Iryo at a speed not yet determined.
The Madrid Seville line is in full “rejuvenation”. The LZB system is being replaced by a much more advanced one, by the European railway traffic management system, ERTMS (reach up to 350 km/h), whose objective is an initiative of the European Union to standardize railway signaling and control systems, guaranteeing interoperability between the networks of different countries. Its level 2, which is what is being implemented, also allows continuous monitoring of speed and braking and radio communication, instead of punctual beacons.
The ERTMS system is installed on the lines that connect the capital with Barcelona, Lleida, Burgos and Valencia; Albacete and Alicante; Valladolid, Palencia and León; and on conventional networks such as at various Cercanías Madrid points.
Railway safety does not depend on a single device. The infrastructure combines signaling systems, train detection mechanisms and blocking procedures aimed at maintaining separation between circulations and avoiding incompatible movements. Among the protection systems is the ASFA (Automatic Signal Announcement and Braking), which transmits information from beacons located on the road. This mechanism installed on all the main lines of the railway network owned by Adif - including the track that connects the center of the peninsula with Andalusia - allows the driver to be informed about certain fixed signals, monitor the speed when approaching them and activate automatic braking in foreseen situations, such as improperly passing a stop signal.
Along with these train protection systems, the railway network has traffic safety systems, which include other components such as locks. According to the Adif network statement, the line where the incident occurred has the Automatic Control Blocking (BCA) system, through which the driver receives all the speed and distance information in the cabin and allows the speed limit to not be exceeded.
In addition, Adif's signaling technical standards (NAS 811) contemplate train detection systems, which are used to divide the track into segments (blocks) and continuously identify the presence or absence of circulation, which allows railway traffic to be managed safely.
Added to all this are the communications systems with the command post. Spanish high-speed lines already have GSM-R, a mobile technology that allows voice and data communications to be established between trains and control centers, through exclusive frequency bands to avoid any type of interference. This system replaces the old analog Train-Land system, which established individual communication between the trains and the command post.
The investigation will have to reconstruct the complete sequence of events, from the eventual breakdown to the order to resume driving and the crash, to determine whether the planned procedures were correctly applied and whether there was any technical or human failure.
