A pedestrian plaza in Times Square has led to "an immediate and substantial" improvement in air quality in the surrounding area, New York City officials said.
The findings, released Wednesday, are from a Health Department air quality study.
The city estimates that a quarter-million pedestrians enter Times Square each day.
Mayor Michael Bloomberg announced the findings at a news conference. He also said he and former President Bill Clinton are merging their environmental efforts.
C40 and the Clinton Climate Initiative both seek to cut carbon emissions through efficient buildings, mass transit and reusing gases emitted by landfills.
Over the past two years, the city has banned cars from parts of Times Square, Union Square and Herald Square.