A technician uses a filler gauge to monitor the rail track switch gap near the Duyun East Railway Station along Guiyang-Nanning high-speed railway in Duyun, southwest China's Guizhou Province, Feb. 27, 2023. The Guiyang-Nanning high-speed railway, with a maximum speed of 350 km per hour, is expected to go into service in 2023. (Xinhua/Liu Xu)