Hundreds of millions of people across China are squeezing into packed train carriages and buses to travel home for the Lunar New Year, in the world's largest annual movement of people. A total of 3.4 billion trips will be made over the holiday period, official media estimates, including hundreds of millions of migrant workers in booming cities who journey to the countryside to spend the season with their families. Travellers must be home by Saturday night to usher in the new year on Sunday.