Train expert: 'I'm baffled by how it happened'
25 July 2013 Last updated at 07:40 BST
A train has derailed in north-western Spain, killing at least 77 people and injuring many more, officials in Galicia region have said.
All eight carriages of the train, which was travelling from Madrid to Ferrol, came off the tracks near the city of Santiago de Compostela.
The Today programme heard that the Spanish newspaper El Pais had reported that the train was over speeding at it approached a bend in the track.
Speaking to presenter John Humphrys, Sim Harris, managing editor of Railnews, said that he was "baffled" by how the incident happened as "modern trains have systems on board to stop over speeding of this extreme kind".
"The ability of the driver to break the rules in this way is very limited by the on board systems of the train," he explained.
First broadcast on BBC Radio 4's Today programme on Thursday 25 July 2013.