The world's longest double-tube four-lane highway tunnel was opened to traffic in northwest China. The tunnel is 18-km long.

The Zhongnanshan highway tunnel, which begins in Qingcha, Xi'an city and ends in Yingpan, Shangluo city in Shaanxi province, allows vehicles to travel up to 80 kmph.

Construction of the tunnel, which runs through the Qinling mountains in Shaanxi, began in March 2002 at a cost of nearly 3.2 billion yuan ($410 million). Japan is currently home to the world's second longest double-tube highway tunnel, which is 10.9 km.

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