Pale blue, fibre-optic-like lines linking dots in an outline of China emerging from darkness -- technology giant Baidu has launched an astronomical chart-style image of the country's New Year travels.

The chart, tracking the mobile phone data of travellers using Baidu's map service, is a visual representation of the world's largest annual human migration and is available at qianxi.baidu.com.

Hundreds of millions of migrant workers are returning home to their towns and villages before the New Year, which begins on Friday, in what is for many their only chance to see their families all year.

Beijing, Shanghai and the southern metropolis of Guangzhou -- the richest cities in China -- had the most departures late morning Tuesday, according to the map.

The top three destinations were the Chinese capital, Chongqing in the southwest and Hengyang, a transport hub in central China offering connections to smaller towns.

The number of road trips reached 97.89 million on Monday, making a total of 1.06 billion since January 16, up 5.4 percent from last year, government news portal people.cn said, citing transport ministry figures.

Transport officials predict Chinese passengers will make 3.62 billion trips during the 40-day New Year period, including 3.2 billion trips by road.