The 'inexplicable' order that put two trains on a collision course in Spain

A collision between two high-speed trains in southern Spain has killed at least 68 people and left scores more injured.

It is the second mass-casualty rail incident to affect the country so far this year, after another crash along the same high speed track in January which killed 46. 

This latest crash, which is already Spain's worst in a decade, will pose further questions about the safety of the country's once-world-leading rail system.

And the tragedy comes in the midst of an election campaign, with authorities now scrambling to explain the "inexplicable" decision that put both trains on a collision course.

What do we know?

The crash happened on Wednesday morning, local time, between two trains travelling along a high-speed rail line south of Madrid.

It is believed one of the trains, belonging to private operator Iryo, was stationary when another train operated by Renfe, struck it while travelling at up to 200 kilometres an hour.

There were more than 500 passengers on the two trains, according to a regional governor.

At least 68 people are dead and more than 80 injured, according to authorities, with aerial footage showing train carriages strewn across tracks and down an embankment.

Ignacio Relaño, a passenger on board, told Spanish public broadcaster TVE that he felt the train "slowing down and then the impact".

"The car leaned to one side like it was about to tip over. I hit my nose, everything went flying, luggage, cell phones. Everything shook."

What went wrong?

Spanish authorities are piecing together the movements of both trains, and how normal safeguards failed to prevent the disaster.

Spain's Transport Minister Óscar Puente said that the accident was caused by what he called the "inexplicable" order from a central command centre for Spain's trains after a security system had failed.

He said the train engineers were not to blame.

Mr Puente said that at 8:30am the security system on a stretch of 63 kilometres stopped working due to a computer malfunction, causing all trains on that stretch to stop. 

But the central command told the Renfe train to start running again without any speed restrictions, and it ended up colliding with the stopped Iryo train at 8:53am.

Mr Puente said that the train should never have been told to start moving again since there was still a “stop signal” active that line, and should never have been allowed to travel at full speed.

"The decision to resume traffic, while that system had not been restored, belongs to the control centre, and the control centre... took the decision to resume traffic in circumstances that, from our point of view, are inexplicable," Mr Puente said. 

Is Spain's rail system safe?

That will be a key question to arise out of this latest tragedy.

Spain's high-speed rail network, operated by state-owned Renfe, was once considered one of the safest and most modern in Europe. 

It is the world's second largest high-speed network, after China's.

But its reputation has been marred by serious safety incidents, including this January's crash along the same rail line, which marked the first fatal incident along Spain's dedicated high-speed rail lines since the network opened in 1992.

Already, Wednesday's disaster appears to be the worst in Europe since 2013, when a lower-speed Spanish train derailed on a curve of track, killing 80.

What are the ramifications?

Following the tragedy, Spain's transport minister failed to rule out resigning.

This second crash in just 10 months comes as Spain gears up for an election on November 29. 

Prime Minister Pedro Sanchez was on his way to the scene of the crash, his office said. The opposition People's Party cancelled all campaign events, a spokesperson said.

This latest crash will pose questions to the country's leaders in Madrid about whether it is competently managing Spain's vast high-speed network.

European Commission data shows Spain's maintenance investment in its roughly 4,000 kilometres of high-speed lines has lagged large European peers, despite an unmatched drive to expand the network.

ABC/wires