Coming Back Full 'Cycle'

"Recognizing that alongside Mexico City, Beijing shares the distinction of being the world's most polluted capital, more than 200,000 Beijing drivers pledged to use public transport, ride a bike or walk to work on that day. "It tells us that many people still reserve a special place for the bicycle in their heart, regardless of there being so many cars on the road," said a civil servant from the Shenzhen Intellectual Property Bureau.

Every 100 Chinese urban families had 162.7 bicycles in 2000, according to the National Bureau of Statistics. That figure dropped to 120 in 2005. Urban sprawl appears to be one reason.

"People's freedom of movement expands after relocation," said Peking University student Cai Zixuan, 21, whose family bought a car three years ago after moving to the West Fifth Ring Road from downtown Beijing."