1. City Efforts to Reduce Car TrafficImagine cities without traffic jams, without cars circling block after block in search of parking. In place of clogged streets and incessant honking, picture urban arteries flowing freely with a mix of cars, public transit, bicycles, and pedestrians. Cities around the world took steps in 2011 to make that vision a reality.

Residents of more than a dozen cities, including Bogota, Montreal, and Zurich enjoyed car-free zones. This year, bike-share schemes gained ground everywhere from the Big Apple to Hangzhou, China, and a growing number of city planners looked to cinch the belt on the supply of parking spaces as a way to steer citizens away from driving.

Related Stories:

"Bike Share Schemes Shift Into High Gear"

"Photos: Twelve Car-Free City Zones"

"With a Deep Dig Into Its Past, Perugia Built an Energy-Saving Future"

"To Curb Driving, Cities Cut Down on Car Parking"

—Josie Garthwaite

Photograph by Peter Macdiarmid, Getty Images

Pictures: Most Hopeful Energy Developments of 2011

While 2011 was a year of nuclear disaster and grim prognostications regarding emissions and energy demand, several bright spots stood out as well, from strides in building efficiency to new green spaces.

December 29, 2011