A railway traffic controller of the Chongqing West passenger train depot wipes sweat off his face while working on a summer outdoor shift in southwest China's Chongqing Municipality, Aug. 17, 2019. (Xinhua/Wang Quanchao)

　　A railway traffic controller of the Chongqing West passenger train depot works on a summer outdoor shift in southwest China's Chongqing Municipality, Aug. 17, 2019. (Xinhua/Wang Quanchao)

　　Train carriages await maintenance at the Chongqing West passenger train depot in southwest China's Chongqing Municipality, Aug. 17, 2019. (Xinhua/Wang Quanchao)

　　A railway traffic controller of the Chongqing West passenger train depot works on a summer outdoor shift in southwest China's Chongqing Municipality, Aug. 17, 2019. (Xinhua/Wang Quanchao)

　　A railway traffic controller of the Chongqing West passenger train depot records a video of the rail track while working on a summer outdoor shift in southwest China's Chongqing Municipality, Aug. 17, 2019. (Xinhua/Wang Quanchao)

　　A railway traffic controller of the Chongqing West passenger train depot works on a summer outdoor shift in southwest China's Chongqing Municipality, Aug. 17, 2019. (Xinhua/Wang Quanchao)