Mechanicians maintain bullet trains in SW China's Chongqing

Two bullet trains wait to be overhauled in southwest China's Chongqing Municipality late at night on Jan. 10, 2020. China, the world's most populated country, on Jan. 10 ushered in its largest annual migration, 15 days ahead of the Spring Festival, or the Lunar New Year. (Xinhua/Huang Wei)