Passengers wait for the train 5639/5640 at a railway platform in Kaili, southwest China's Guizhou Province, Jan. 11, 2018. The train 5639/5640, a pair of low-speed trains in service for many years and stop at trivial stations along the mountainous area from Guiyang to Yuping, have assumed an important role in providing travel service to local people. (Xinhua/Wu Jibin)