Every winter, hundreds of millions of Chinese return home for the Spring Festival, the Chinese celebration of the Lunar New Year (which this year lands on January 31).

The mass migration, known in Chinese as chunyun, is on track to reach an unprecedented scale in 2014. According to Lian Weiliang, the deputy head of China's National Development and Reform Commission, an estimated 3.62 billion trips will be made during the 40-day period surrounding the holiday, an increase of roughly 5.8 percent, or 200 million trips, compared with 2013.

Simply put, it is the largest annual human migration in the world.

Baidu, China's dominant search engine, has now made it possible to visualize this tremendous pilgrimage, unveiling a map that displays Spring Festival travel routes and their popularity over rolling eight-hour periods. To create the map, Baidu used location-based data from its mobile software products to track travelers during the 40-day period. As of August 2013, Baidu was receiving 3.5 billion requests per day for GPS location on its cellphone products, making it the largest source of location data in the People's Republic of China.

Go Home or Face the Wrath of Parents

For migrant workers, many of whom face demanding jobs far from their hometowns, the Spring Festival presents a once-a-year opportunity to return home and reunite with their families.

"It's not always easy to afford train tickets, and the journey can be tedious and unpleasant," said Zhang Xuan, a 25-year-old graphic designer who is traveling from Beijing to her hometown in central China's Henan Province. "But not returning home is not an option-my parents would kill me."

According to Liang Xiao'an, a spokesperson for the Ministry of Transport, about 3.2 billion trips are expected to be made by road, including long-distance buses and an increasing number of private cars. Roughly 258 million train trips will be made during the period, while another 42 million people are expected to fly home.

The Baidu map allows users to view the country's most traveled routes (in Chinese only), with a feature that ranks cities based on the number of departures and arrivals that they record. To no one's surprise, Beijing and Shanghai, two of China's most populous cities, were consistently at the top of these charts on Thursday, the eve of the Lunar New Year.

Based on the map, most of the routes are concentrated in China's eastern region, particularly in the southeast, where rapid economic development has lured migrant workers from all corners of China. By contrast, the country's western region, which includes Tibet, Inner Mongolia, and the predominantly Uighur province of Xinjiang, remains mostly untraveled.

Why the Sky Loves the Migration

In Beijing, the Spring Festival results in a mass exodus of roughly one-third of the city's estimated 20 million people. The capital's second ring road, which is typically congested with bumper-to-bumper traffic, is left wide open, while Beijing's subways, normally jam-packed with commuters, are empty and serene.