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A picture taken on July 24, 2013 shows derailed cars on the site of a train accident near the city of Santiago de Compostela. Up to a dozen people died when a train derailed in northwestern Spain today, media reports quoting witnesses said. The train which carried 238 passengers originated in Madrid and was bound for the northwestern town of Ferrol. AFP PHOTO / MIGUEL RIOPAMIGUEL RIOPA/AFP/Getty Images
A picture taken on July 24, 2013 shows derailed cars on the site of a train accident near the city of Santiago de Compostela. Up to a dozen people died when a train derailed in northwestern Spain today, media reports quoting witnesses said. The train which carried 238 passengers originated in Madrid and was bound for the northwestern town of Ferrol. AFP PHOTO / MIGUEL RIOPAMIGUEL RIOPA/AFP/Getty Images

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Expert: Train may have gone too fast

Railroad safety expert Gary Wolf explains some of the factors that could cause a train to derail.

Expert: Train may have gone too fast

Railroad safety expert Gary Wolf explains some of the factors that could cause a train to derail.