China, the world's most populated country, on Friday ushered in its largest annual migration. Bullet trains are under maintenance for Chinese Spring Festival travel rush in Chengdu, capital city of southwest China's Sichuan Province. The 40-day travel rush is known as chunyun in Chinese. The Lunar New Year falls on Jan. 25 this year, earlier than previous years, which brings a bigger challenge to the transport system as the return trips of college students overlap with the travel rush. To meet the rising travel demands, a total of 5,275 two-way train services will be scheduled daily before the festival, up 7.7 percent year on year, hitting a record high, said Li Wenxin, vice general manager of the China State Railway Group Co. Ltd. China's high-speed railway network tops the world with an estimated length of 35,000 km by the end of 2019, according to China Railway. Bullet trains handled 2.31 billion passenger trips in 2019, representing a 3.4-fold increase from 2012.■