A total of 68 people have been killed so far in yesterday’s severe collision between 2 high-speed trains in Spain.

The investigation into the causes of the train crash is in full swing, but all signs point to possible human error. The accident is believed to have been caused by an “inexplicable” and “wrong” decision by traffic control that allowed the Renfe train to proceed despite the red signal.

In the train accident, which occurred near the town of Urda, about 130 km south of Madrid, an AVE high-speed train operated by the state-owned company Renfe rear-ended a stationary high-speed train operated by the private railway company Iryo.

Meanwhile, the Spanish train drivers’ union, Semaf, has begun a 24-hour strike. The strike had already been announced in mid-October and went ahead as planned, despite the tragedy – more than 100 people were injured, about 50 of whom remain hospitalized.

Among other things, the strikers are demanding structural improvements to safety and maintenance on the Spanish rail system, which is under pressure due to the great success of the high-speed network.

Audio recordings revealed

An audio recording of the conversation between the traffic controller and the driver of the HST train, posted on YouTube by the Spanish newspaper El País, reveals that the control center at the Antocha station complex in Madrid decided to resume train operations after approximately 6 minutes following a technical malfunction in the LZB automatic safety system.

The AVE followed the instructions and continued on its way. Still, according to safety protocols, the train should have been operating “on sight”, with a strict speed limit, rather than accelerating – it’s possible that the operator read the wrong line of the protocol, but that has not yet been confirmed.

The Iryo train operator received the same instruction 5 minutes later, but called again shortly afterward because she was still at a standstill due to communication problems.

As a result, the AVE was heading toward the stationary Iryo on the same busy track between Madrid and Seville, where, at that moment, 4 other trains had automatically stopped over a stretch of about 69 km due to the LZB failure.

In the recordings, the traffic control center acted as if the 2 trains were not in the same block section, even though it could have slowed down the oncoming train and prevented the fatal head-on collision – though the investigation will have to determine why that was the case.

Second serious train accident on Spanish rail

This is already the second serious train accident on the Spanish rail network in a short period of time. In January, an Iryo high-speed train derailed in Adamuz, causing several cars to end up on the adjacent track, where an oncoming Renfe Alvia train struck them at full speed. Forty-six people were killed in that collision. The cause is believed to have been a defective weld between two rails.

With over 3,900 km of HST rail, Spain has the largest HST rail network in Europe and the second-largest in the world, after China. And according to the Spanish news agency EFE, Adamuz and Urda are the only 2 fatal accidents since high-speed rail began in 1992.

Moreover, when you consider that in 2025 it reached a record number of 43,8 million passengers per year, this fits the pattern that trains are much safer than cars – although air travel still scores slightly better, also because flying is made to look better per kilometer due to the long distance involved, since takeoff and landing are the riskiest phases.

HST rail network under pressure

But precisely because of that great success, the Spanish HST rail network – on which 3 different train operators are active – is also under pressure.

For example, too much attention is reportedly being paid to expanding the network and increasing service—on the busy route between Madrid and Seville, for instance, the number of trains increased by more than 12% in a single year—and not enough to maintain the infrastructure.

The figures speak for themselves: in France and Germany, reportedly about one-third of the budget goes toward maintenance, compared to 16% in Spain.

Before the accident, train operators had also warned of recurring malfunctions in the signal systems. There were also reportedly problems with spare parts for the LZB railway system, the automatic safety system that continuously monitors trains’ speed and position on the Madrid-Seville line.

The system on that line is being replaced with the latest European signaling system (ETCS), but the replacement has been delayed.

Outdated

LZB stands for Linienzugbeeinflussung, or “track-based train control.” The German system, which uses a physical loop (cable) in the track, continuously tells the train how fast and how far it is allowed to travel safely, and automatically intervenes if the train operator fails to do so.

However, the system is considered outdated, partly because the manufacturer stopped supporting the version used in Spain, and it is therefore being replaced by ETCS, the latest European safety system that has already been fully implemented in Belgium, for example — one of the few countries in Europe where this is already the case.

In Spain, that transition is now proceeding much more slowly, though it’s not as bad as it could be: the Madrid–Seville high-speed line is apparently the only Spanish high-speed line that still uses it.

Experts say that the ETCS system, which uses radio and electronic transponders, should have been operational in 2024. The deadline was then pushed back to 2025, then to April 2026, and it is still not operational. It is not known whether this delay is related to the accident.

If the LZB system fails, operations switch to the light signals along the track (BSL), with ASFA providing safety protection. ASFA operates only from beacon to beacon and therefore offers much less continuous protection. Traffic control must then determine on its own who is allowed to run and when. This is exactly the situation that led to the collision near Urda.

A properly functioning ETCS would likely have reduced the likelihood of the accident, since in ETCS fallback modes it could still have monitored speed—typically down to about 40 km/h—but it would not necessarily have prevented it.

After all, ETCS can also fail. In that case, it switches to a fallback mode in which the decision rests once again with the train operator and traffic control.

Angry train conductors

The reason the SEMAF train operators’ union is going on strike right now is that it believes safety on the rail network is not improving enough. According to SEMAF, a commission was formed after the accident in Adamuz.

Still, since then everything has come to a standstill, and agreements with the ministry, rail operator Adif, the safety agency AESF, and Renfe are being blocked by red tape.

SEMAF is calling for binding protocols for weather warnings, clear rules for communication in high-risk situations, and proper enforcement of mandatory breaks in driving.

The union also wants definitive technical solutions to safety and reliability issues affecting rolling stock, as well as the release of the coefficients that enable early retirement. In addition, the issue concerns the hiring of new train operators.

Spanish train operators also point out that track maintenance is carried out by private companies and warn of the deteriorating condition of the tracks and rolling stock.

So it looks like, in addition to the technical and legal investigations, there will also be a fierce battle of wills between the railway unions and railway companies on one side and the transportation minister—who refuses to resign—on the other.

Prime Minister Sánchez has already made it clear that there will be a strong response to any flaws in the safety system. He also promises to strengthen safety and restore confidence in the high-speed rail system.

It also remains to be seen how significant the accident’s impact will be on the upcoming general election on November 29.