BEIJING, Dec. 29 (Xinhua) -- China aims to build a comprehensive transport system, with a faster, greener and safer network to offer more efficient services to the public by 2020, according to a white paper released on Thursday.

A test train in seen on the Guizhou West section of the Shanghai-Kunming high-speed railway, Dec. 17, 2016. China on Wednesday put into operation one of the world's longest high-speed railways, linking the country's prosperous eastern coast to the less-developed southwest. The Shanghai-Kunming line -- 2,252 km in length -- traverses the five provinces of Zhejiang, Jiangxi, Hunan, Guizhou and Yunnan and cuts travel time from Shanghai to Kunming from 34 to 11 hours, according to China Railway Corporation. (Xinhua/Ou Dongqu)

The white paper, titled "Development of China's Transport," reviewed the sector's tremendous changes in past decades and set goals for its further expansion in coming years.

The sector should quicken its pace of development, and fully play its basic role as a vanguard for completing the building of a moderately prosperous society in all respects in 2020, said the document issued by the State Council Information Office.

By 2020, China will increase the length of high-speed railways in operation to 30,000 kilometers, connecting more than 80 percent of its big cities.

The country will also renovate 30,000 km of expressways and provide tarmac and cement roads and shuttle bus services for administrative villages with the necessary conditions, while all villages will have access to mail service, it said.

Over the past decades, China's transport network has undergone drastic changes, especially the railway sector.

When the People's Republic of China was founded in 1949, total railway length was only 21,800 km, half of which was paralyzed.

Thanks to a series of reforms since then, total railway operation length reached 121,000 km by the end of 2015, the world's second longest, including 19,000-km high-speed railway, ranking top of the world.

While the vast network has enhanced connectivity in large swathes of the country, disparity remained as construction has lagged behind in the less developed western regions, and in recent years, the government is seeking to narrow the gap.

The white paper pledged to speed up the construction of railways in the central and western areas.

China on Wednesday put into operation one of the world's longest high-speed railways, linking the country's prosperous eastern coast to the least-developed southwestern region.

The Shanghai-Kunming line -- 2,252 km in length -- traverses five provinces of Zhejiang, Jiangxi, Hunan, Guizhou and Yunnan and cuts travel time from Shanghai to Kunming from 35 to 11 hours, according to China Railway Corporation.

Also on Wednesday, another high-speed rail line linking Kunming and Nanning, capital of southwest China's Guangxi Zhuang Autonomous Region, was launched.