Authorities in China have come up with an unlikely solution to tackle this city’s infamous traffic problems — building massive 60-metre-deep underground tunnels that will take the load off the Chinese capital’s gridlocked streets.

Beijing will start building the underground roads this year, Mayor Guo Jinlong told an annual legislative meeting on Sunday. The tunnels will be built alongside one of the six circular expressways, or ring roads, that run around the Chinese capital. The six ring roads were built in the 1990s to plan ahead for the city’s expansion and growing traffic needs.

But in spite of Beijing’s impressive urban infrastructure network of elevated highways and an extensive metro rail subway system, the city has struggled to cope with the surge in number of cars on its roads driven by a fast-growing and increasingly aspirational middle-class.

China last year overtook the United States to become the world’s largest car market. The number of vehicles in Beijing alone is estimated to reach 7 million by 2015.

The underground tunnels, which will be built along the often clogged Second Ring Road, will be as deep as 60 m, the China Daily reported on Monday. “Because of the complex underground pipeline systems, geological conditions and abundance of historical relics, these will be the world’s most difficult tunnels to dig,” Zhou Nansen of the Beijing municipal commission of urban planning told the newspaper.

The tunnels are the latest of a number of measures that have been announced recently to address the traffic problem, which famously resulted in a 10-day-long traffic jam in a Beijing suburb in August. This was followed by a record 140 simultaneous gridlocks a month later in the city, after heavy rains.

Among the new measures is a system to cap the number of licence plates issued annually at 240,000, down from 890,000 last year. Licences will now be issued through a lottery system. For January alone, more than 210,000 people applied for 20,000 available licences.

Shanghai, in China’s south, already has in place a similar system of capping the number of licence plates, which are auctioned to the highest bidder every month.

But urban planners say the only long-term solution to Beijing’s traffic situation is improving its public transport system. The city is investing $50 billion in the next five years to double its 336 km subway network.

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