A bullet train runs on a bridge of Xi'an-Chengdu high-speed railway during a test in northwest China's Shaanxi Province, Nov. 1, 2017. The Xi'an-Chengdu line is China's first rail route to run through the Qinling Mountains, which are the natural boundary between north and south China. It will begin operation on Dec. 6. (Xinhua/Tang Zhenjiang)