Talking to the BBC, City University Professor David Stupples said the system, designed to improve railway interoperability and safety across the continent, could be breached by hackers seeking to wreak havoc on the railways. 

The major concern, he said, is malicious software that could be inserted into the system, possibly even by an insider, to cause trains to crash.

"It's the clever malware that actually alters the way the train will respond,” Stupples said. “So, it will perhaps tell the system the train is slowing down, when it's speeding up."

The European Rail Traffic Management System (ERTMS) will replace traditional railway signals with a computer display inside every train cab. The computer will be able to take care of the speed and movement of the train while considering other trains in the vicinity.

First trials of the ERTMS in the UK commenced in 2008. Network Rail is in charge of the roll out, with the system expected to be fully operational by the 2020s.

 http://eandt.theiet.org/news/2015/apr/network-management-system-cyber-security.cfm