A deadly train crash in China over the weekend has raised concerns about the safety of the country's fast-growing rail network..."[S]ince 2008 China has experienced...a 'great leap forward' of railway construction," said Ren Xianfang, a senior analyst at IHS Global in Beijing. "We've long had suspicions that this speed of construction is unsustainable." The main problem...[is] under-investment in the software infrastructure...A spokesman for China South Locomotive, which built both trains in a joint venture with Canada's Bombardier, said signalling operations were to blame for the crash. "The quality of the trains is fine. Neither had any accidents previously. It's the signaling system that went wrong," he said...[refers also to Bombardier]