Conductor Zhang Xinxin (2nd R) helps a wheelchair user on the bullet train D6093 at the Yantai Railway Station in Yantai, east China's Shandong Province, June 30, 2018. China's summer transport peak period will begin on July 1, with a total of 647 million passenger trips expected to be made by train. The period runs from July 1 to August 31, when students on summer vacation have time to travel or return home. (Xinhua/Tang Ke)

Children board a bullet train at the Yantai Railway Station in Yantai, east China's Shandong Province, June 30, 2018. China's summer transport peak period will begin on July 1, with a total of 647 million passenger trips expected to be made by train. The period runs from July 1 to August 31, when students on summer vacation have time to travel or return home. (Xinhua/Tang Ke)

Passengers board a train at the Yantai Railway Station in Yantai, east China's Shandong Province, June 30, 2018. China's summer transport peak period will begin on July 1, with a total of 647 million passenger trips expected to be made by train. The period runs from July 1 to August 31, when students on summer vacation have time to travel or return home. (Xinhua/Tang Ke)

A passenger boards a bullet train at the Yantai Railway Station in Yantai, east China's Shandong Province, June 30, 2018. China's summer transport peak period will begin on July 1, with a total of 647 million passenger trips expected to be made by train. The period runs from July 1 to August 31, when students on summer vacation have time to travel or return home. (Xinhua/Tang Ke)