A new wave of mass urban rail transit construction is set to kick off soon with the National Development and Reform Commission approving plans of 19 cities.

About 2,100 km of railway lines will be laid and operational by 2015 in the 19 cities, Dou Hao, the deputy general manager of China International Engineering Consulting Corporation (CIECC), said Tuesday at a press conference for Metro China 2009, the biggest exhibition of its kind in China held in November.

The projects will involve an investment of at least 800 billion yuan ($117 billion), he said.

CIECC has been authorized by the NDRC to assess the cities' metro planning, based on which the NDRC will give its nod to the project.

The urban rail projects are bigger than projected last year, when 15 cities were given the green signal to build railway systems, totaling about 1,700 km at a cost of 600 billion yuan.

"The increase is a result of government measures to boost economy. It's very quick to have a railway project approved," Zhou Xiaoqin, director of transport project department with CIECC, said.

Nine other cities, including Fuzhou, Nanning, Guiyang and Kunming, have submitted their plans and are awaiting approval, he added.

"China has risen to be the world's largest urban rail transit construction market," Jiao Tongshan, vice-chief of China Communications and Transportation Association, said at the conference.

At present, 14 cities are building 46 urban rail lines, which total 1,212 km, he said.

With traffic congestions plaguing most major cities, local governments agree an efficient urban rail network is the only answer, Dou said.

At present, 3.5 million people in Beijing and 3.07 million people in Shanghai use subways and light rails every day, accounting for a fifth of the total population using public transport, Dou said.

Beijing is expected to become the city with the longest urban rail, with plans to build 18 routes stretching 561 km.

It now has eight lines in operation, totaling nearly 200 km. At present, six lines are under construction, involving an investment of 90 billion yuan.