Few pedestrians are seen on a street near Jianwai SOHO in Beijing, Feb. 17, 2015. (Photo: China News Service/Jin Shuo)

Transportation peaked in major cities across China on Monday as millions of people began their annual migration trips back home for the upcoming Spring Festival.

The travel spree, known as chunyunin Chinese, is the world's largest migration, as hundreds of millions of people attempt to get back home before the lunar New Year eve on February 18.

More than 80 million trips were made on high-speed rail on Monday. An estimated 2.8 billion railway trips will be made during the holiday, meaning an average of 70 million trips every day over the entire 40 day period from February 4 to March 15, the Xinhua News Agency reported, but in practice travel clusters heavily around the seven-day holiday.

Railway authorities in Shanghai estimated the number of passengers leaving the city at 400,000 and the number could top 410,000 on February 17. Last year's travel peak saw a total of 365,000 trips per day, according to the China News Service.

"February 16 and 17 will see the last groups of people leaving Beijing, most of whom work for government bodies and public institutions. Students and migrant workers already left the city as early as mid January," an official at Beijing Railway Station told the Beijing Morning Post.

Beijing West Railway Station had sent off more than 230,000 passengers by Monday afternoon, and the station is expected to see a total of 420,000 travelers leaving or passing through Beijing on Monday.

Meanwhile, Beijing is likely to suffer serious pollution caused by firecrackers during the Spring Festival, while the weather conditions from February 18 to 20 in the capital cannot effectively help disperse pollutants, Li Yunting, an official with the Beijing Municipal Environmental Monitoring Center, said on Monday.

The local government approved 942 firecracker retail spots this year, 100 fewer from last year, and authorities have also cut the number of permitted sales days amid pollution concerns.