Workers in Beijing leave their city jobs and return home to villages to celebrate the Chinese New Year.
This is part of the world's largest annual human migration.
Authorities struggled to cater to an unprecedented 3.1 billion passenger trips over 40 days, according to the state news agency.
(SOUNDBITE) (Mandarin) CONSTRUCTION SUPPLIES SALESMAN YU GUOXIN SAYING:
"Going home is to reunite with the whole family. The family spends the Chinese New Year together and have a happy new year. My parents are still back at home. So I must go home."
Just over 51 per cent of China's 1.35 billion mainlanders lived in towns and cities at the end of 2011, meaning the urban population had finally overtaken the rural population after three decades of rapid growth.
But although China's army of rural-to-urban migrants build the skyscrapers, sew the clothes, and tend the shops, they remain outsiders.
(SOUNDBITE) (Mandarin) SOCIOLOGIST OF RENMIN UNIVERSITY ZHOU XIAOZHENG SAYING:
"Last year the urban population started exceeding the rural population, but there is a problem. Before, when China was a closed society it had two social groups: urban and rural residents. But now we have several hundred million migrant workers -- a third group, who live in the city but they can't get a residence permit, so they all go home for the Chinese New Year. So our urbanisation is incomplete."
China's household registration system means rural-urban migrants cannot register as city residents, and therefore cannot receive the same benefits as urban residents.
Here in Chongqing, a city of eight million on the Yangtze River in southwestern China, the municipality allows rural residents to become urban citizens after three years living in the city.
According to the mayor, "there is no discrimination against farmers at all", and migrant workers receive the same old age benefits, health insurance, and access to housing, and their children can go to school.
But until reforms such as these become national policy, China's migrant workers will continue to make the long New Year's journey back to their villages, the only places they can really call home.
Nick Rowlands, Reuters.
