HONG KONG - Efficient public transportation systems have contributed to London's low-carbon commitment, and this system can serve as a role model for other mega-cities like Beijing in their pursuit of sustainability, experts said at a climate change conference in Hong Kong on Thursday.

Once a "high carbon" city, London is aiming for a 60 percent cut in CO2 emissions by 2025, according to Nicky Gavron, a member of the London Assembly and former deputy mayor of London.

Gavron said that 22 percent of London's CO2 emission used to come from the city's transportation sector, so "getting transportation right became central in their vision" of building a low carbon London.

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Gavron it's been "tough" to make the city's air better, but she stressed that regulations change attitudes and attitudes changes behavior.

The city encourages people to use public transit by adding more bus lanes, and making it free for seniors and the young to take a bus. Gavron said transportation reform in London is proving a success, and greenhouse emissions are declining.

She also proposes traffic congestion charges to reduce congestion, which will also help in emission cuts and also make more people choose public transportation.

For a mega-city like Beijing, authorities should also encourage people to take public transportation, said Zou Ji, China chief director of the World Resources Institute.

People might change their working and traveling patterns if the city sets up small working centers among communities, and this would make Beijing more accessible, Gavron told chinadaily.com.cn.