New York City has focused on reducing its environmental impact and carbon footprint.[441] Mass transit use in New York City is the highest in the United States. Also, by 2010, the city had 3,715 hybrid taxis and other clean diesel vehicles, representing around 28% of New York's taxi fleet in service, the most in any city in North America.[442]
New York's high rate of public transit use, over 200,000 daily cyclists as of 2014,[443] and many pedestrian commuters make it the most energy-efficient major city in the United States.[444] Walk and bicycle modes of travel account for 21% of all modes for trips in the city; nationally the rate for metro regions is about 8%.[445] In 2011, Walk Score named New York the most walkable city in the United States.[446][447] Citibank sponsored the introduction of 10,000 public bicycles for the city's bike-share project in the summer of 2013.[448] Research conducted by Quinnipiac University showed that a majority of New Yorkers support the initiative.[449] New York City's numerical "in-season cycling indicator" of bicycling in the city hit an all-time high in 2013.[450]
The city government was a petitioner in the landmark Massachusetts v. Environmental Protection Agency Supreme Court case forcing the EPA to regulate greenhouse gases as pollutants. The city is also a leader in the construction of energy-efficient green office buildings, including the Hearst Tower among others.[134] Mayor Bill de Blasio has committed to an 80% reduction in greenhouse gas emissions between 2014 and 2050 to reduce the city's contributions to climate change, beginning with a comprehensive "Green Buildings" plan.[441]