Cao Youfeng gets ready to begin his day at a locomotive depot in Xuzhou, Jiangsu province, Jan 15, 2017. [Photo/VCG]

The world's largest annual human migration for family reunion, also known as "Chunyun", started last Thursday in China. In order to maintain the smooth operation of trains during the 40-day Lunar New Year travel rush, many railway employees are working around the clock. Cao Youfeng is one of them.

Cao is a veteran. After retiring from military, he began working 36 years ago as a bench worker at a locomotive depot in Xuzhou, Jiangsu province. Cao said overhauling the trains carefully is vital, and he should guarantee the safety of trains before departure.