Passengers walk to board their train at the Beijing Railway Station, in Beijing, capital of China, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year. (Xinhua/Zhang Chenlin)

Passengers place their luggage on the overhead rack on the train 3603 from Beijing to Chongqing, in Beijing, capital of China, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year. (Xinhua/Zhang Chenlin)

A passenger walks through the infrared temperature measuring area when entering the Beijing Railway Station in Beijing, capital of China, Jan. 27, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year. (Xinhua/Zhang Chenlin)

A train driver makes preparations before departure on the train 3603 from Beijing to Chongqing, in Beijing, capital of China, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year. (Xinhua/Zhang Chenlin)