China's bullet train system still faces many unpredictable risks and any small error could bring another crisis upon the giant Ministry of Railways, industry insiders warn. While the ministry raised the speed of its top-of-the-line trains from about 100 km/h up to 350 km/h in just a decade, train drivers and other industry insiders said the system as a whole was far from reliable. Max Zhou, who was a train driver for three years with the Guangzhou Railway Group before he left two years ago, said relations between employees and middle and senior management had deteriorated dramatically during the period of breakneck growth in the sector. 'The staff were under great pressure. It felt like a spring getting tighter. We had hoped the development of the high-speed railway would provide us with better lives and higher income, but we were wrong.' He said the middle management was old-fashioned, which could trigger industrial conflict in the future. The lack of transparency in the ministry's procurement process is another cause for concern. The ministry invites and approves suppliers and contractors through its 'administrative permission system', but how this operates is largely a mystery. Critics have described the process as 'black-box operations' and raised suspicions that many suppliers had won contracts through bribery or connections rather than quality, suitability or value for money. Zhou's concerns were echoed by a well-placed industry insider. A senior member of staff at the Beijing Railway Bureau who did not want to be named told the Guangzhou-based Southern People Weekly last month that technically only products from suppliers with licences issued by the ministry could be used for the railway system. 'But this doesn't mean you will get the required licences simply because your products are good ... you have to work for them,' the staffer said, referring to bribery. 'There are too many black-box operations under the administrative permission system,' he said. 'But the risks of this are high. We all know that any [substandard] screw, nut or even a tiny shim can malfunction with very bad results.' The source said he was also constantly worried that many maintenance workers had no experience or qualification to deal with the sophisticated bullet train system.