In the days and weeks before Chinese New Year, some 700 million people—twice the entire population of the U.S.—cram onto trains, buses, planes and boats to go home. This mass migration is the largest annual movement of humans in the world, and now it can be tracked by smartphone.


For the past couple years, Chinese internet giant Baidu has traced the travel of people using its smartphone maps. Big industrial cities like Beijing, Shanghai, and Shenzhen light up as major hubs.

What's less obvious in Baidu's visualization, though, is the direction people are going. During Chinese New Year, big cities become empty, near-ghost towns, as millions of migrants workers return home for the holidays. There's a saying in Chinese: 有钱没钱回家过年, or which roughly translates to "Rich or poor, go home for the new year." For migrant workers, the weeklong holiday around Chinese New Year is often the only opportunity for them to see the parents and children they left behind in rural villages.


Travelers waiting in line outside of Beijing's train station on Tuesday, February 17, 2015. AP Photo/Andy Wong

Of course, this massive and lopsided migration puts a huge strain on the China's transportation infrastructure. The China's National Development and Reform Commission estimates that 3.62 billion trips are made in the 40 days around the lunar new year.

The biggest crush is on the railways, as most Chinese cannot afford to fly or drive. Temporary trains are pressed into service. Temporary ticket stations spring up. In spite of these measures, people with standing tickets are packed onto trains until there's barely room to move. You even get the occasional story about adult diaper sales peaking before the holiday travel season, as travelers tuck in for their long-haul journeys.


Temporary ticket station in Hefei for Chinese New Year travel. Credit: Vmenkov/CC


And that's only half of it. After the holiday, which is on February 19 this year, the entire country embarks on return journeys, cramming back into the major cities until next year, when happens all over again.

Top image: Baidu