Zhao Haizhou, a mechanic of bullet train, checks the bottom of a train at a maintenance station in Changchun, capital of northeast China's Jilin Province, Jan. 21, 2019. Zhao and his colleagues conduct a comprehensive safety check for over 20 bullet trains on Monday morning, the first day of Spring Festival travel rush, especially to ensure that trains could operate safely in low temperature in winter. (Xinhua/Zhang Nan)