Two young passengers board a train with their guardian on Jan 5, 2014 at the Hangzhou Railway Station in Hangzhou, Zhejiang province. [Photo / IC]

BEIJING - China Railway Corporation (CRC), operator of China's rail network, started to sell train tickets for the 40-day travel period known as "chunyun" on Sunday.

"Chunyun", sometimes called the world's largest human migration, is the hectic travel period surrounding Chinese New Year. This year, chunyun will begin on Feb 4 and last until March 16.

Chinese New Year celebrations, known as Spring Festival, are China's most important holiday of reunion, with hundreds of millions of people traveling to their hometowns to spend time with relatives, putting huge stress on transportation system.

The upcoming Spring Festival falls on Feb 19.

During chunyun 2014, about 266 million trips were made on railways, up 12 percent from the previous year.

From Sunday, passengers can book tickets for departures on Feb. 4 through the Internet or by phone.

For chunyun 2015, the corporation plans to run 3,063 pairs of trains, an increase of 335 pairs from 2014.