A railway policeman warns passengers of travel safety rules at a low-speed green train from southwest China's Chongqing Municipality to Neijiang City of southwest China's Sichuan Province, Jan. 31, 2019. Low-speed green trains are still in operation as bullet trains run past new stations throughout China. The old-fashioned green trains are a low-cost alternative for people to travel during the 2019 Spring Festival travel rush. (Xinhua/Liu Chan)