Beijing's metro system will stretch to 561 kilometres by 2020, replacing London's Underground as the longest subway system in the world, according to a recently completed construction plan for the capital city's public transportation offerings.

According to the plan, the 561 kilometres will be laid out along 19 lines knit together beneath the capital.

Unlike metro lines 1 and 2 (the loop lines), which encircle the Tian'anmen Square area, the traditional city centre, the new lines are expected to reach all the major corners of the capital.

Fifteen of the new lines will support urban areas, while the remaining four will stretch out to the suburbs, according to the plan drafted by the city's communications commission.

Zhao Hui, a researcher who helped draft the plan, said it represented a long-term vision and was therefore subject to change. The city's Development and Reform Commission still has to approve the plan, he noted.

The three lines Line 4, 5 and 10 that are currently under construction are expected to be operational for the 2008 Olympic Games.

Line 4 will connect Fengtai in the extreme south with Haidian in the northwest, spanning 28.16 kilometres. This line will represent the first direct link between Beijing's two "poles."

Line 5 will serve a similar function, creating a short-cut route between the "developed" north and "developing" south, from Changping to Fengtai districts.

The city is also building Line 10, which will proscribe an arc whose tips will be Haidian and Chaoyang districts. This line will link up the northwestern and eastern-southeastern sections of the city.

A 5.91-kilometre section of Line 10 is aimed at easing travel relating to the 2008 Olympic Games.

Zhao said Line 11 would be finished in 2012 and link with Line 10. The new loop line created by the two linked lines will thread through major city centres including Zhongguancun technology zone, the CBD and the Olympic zone.

Currently four metro lines serve Beijing. Lines 1 and 2 span 54 kilometres, while Line 13 and Line Batong cover 61 kilometres. Together they carry 1.5 million travellers every day.

Beyond building new subway lines, transportation experts have been exploring other possibilities for the city's underground space to help ease the traffic pressure.

During a conference this weekend entitled the "International Academic Conference on Underground Space," the Beijing Urban Planning Commission and Beijing Urban Planning and Designing Research Institute jointly released a new plan proposing the construction of six underground expressways by 2020 to further ease traffic congestion, mainly within the second and third rings.

Shi Xiaodong, a senior planner with the planning and design research centre, said moving more transportation underground will help eliminate noise pollution and reduce traffic in the old urban area.

However, Duan Liren, an expert with the Beijing Transportation Management Engineering Institute, warned the involved officials to be cautious about developing the underground express system.

"Such a large-scale underground expressway system would be unprecedented in the world, and we have little experience to draw upon. The technological difficulties and construction costs of this system will exceed those of the metro system," Duan was quoted by the Beijing News as saying.

(China Daily November 20, 2006)