People in China will make 3 billion trips in the next 40 days to celebrate Lunar New Year, the world's largest annual human migration

Chunyun, also known as Chinese New Year or Spring Festival, has begun.

Source: CNN

Over 40 days, from January 10 to February 18, about 3 billion trips will be made by travelers on the move.

Source: CNN

Stations are already filling with masses of passengers waiting for buses, trains, planes, and ferries.

It's the largest annual human migration in the world. By comparison, the annual Hajj pilgrimage to Mecca usually includes about 2 million people.

Sources: China Daily, CNN, Business Insider

While China follows the Gregorian calendar, its holidays are based on the moon's movements. This year, the Lunar New Year falls on January 25.

China celebrates for another 15 days after that. The Year of the Pig ends, and the Year of the Rat begins.

Sourc: CNBC

As China celebrates, red decorations are used everywhere. The color represents prosperity.

Source: National Geographic

The point of Chunyun is to celebrate family. It's focused on reunion and hope.

Source: National Geographic

Fireworks and lantern festivals are part of it, too, though they've decreased some as the government has tried to improve air quality. As of 2018, about 444 cities had banned or limited fireworks sales.

Sources: National Geographic, Global Times

In such a large country, with a population greater than 1 billion, the celebration is an annual headache for airports and train stations.

Sources: National Geographic, Smithsonian Magazine, CNN

It's the earliest Chinese New Year in eight years, and could result in additional congestion issues since the holiday overlaps with university students' winter holidays.

Source: CNN

Peak travel days are expected to be January 20 to January 22, and January 31 to February 1.

Source: CNN

One of the main causes of congestion is China's commuting work population. About 20% of China's population lives in rural areas but travels to cities to work, and many of them head home for the holiday.

Source: Smithsonian Magazine

Thousands of train services will be running to keep people moving, including bullet trains that go 185 mph. The country unveiled one that can go 217 mph last week.

Sources: CNN, Business Insider

Staff have been prepped and ready to work on the largest rail network in the world.

Source: CNN

According to Chinese government estimations, of the 3 billion trips, 440 million will be by train. Since last year's festivities, China built about 5,275 miles of new railroad.

Sources: China Daily, CNN

China's government is also giving discounted tickets to people who take a "reverse route," trying to incentivize people to leave their rural towns and go celebrate in cities.

Source: China Daily

Even so, the majority of journeys will be in cars. China's government estimates there will be about 2.43 billion road trips. This is a motorway during the holiday season back in 2018.

Source: CNN

It's a slow, tiring trip for many.

And the stress on infrastructure is no laughing matter. In 2016, snow and freezing temperatures stranded 100,000 people at a single train station. China deployed 2,600 police guards to to maintain order.

Source: The Guardian

Some Hong Kong protesters are using the holiday to continue calling for independence from China. As recently as January 1, 400 protesters were arrested during a march that turned violent.

Source: NBC News

For many, Chunyun is the best part of the year, and worth the congestion to see friends and family.