Study: City Living Helps Limit CO2 Emissions

The Chicago-based nonprofit Center for Neighborhood Technology looked at emissions of carbon dioxide, a key greenhouse gas, stemming from household vehicle travel in 55 metropolitan areas across the United States.

When measured on a per household basis, researchers found that the transportation-related emissions of people living in cities and compact neighborhoods can be about 70 percent less than those living in suburbs.

"Cities are more location efficient - meaning key destinations are closer to where people live and work," said Scott Bernstein, president of the Center for Neighborhood Technology.

Wizard travels the New York City subway, reducing greenhouse gas emissions and providing entertainment at the same time. (Photo by Michael Mulvey)

"They require less time, money, fuel and greenhouse gas emissions for residents to meet their everyday travel needs. People can walk, bike, car-share, take public transit," he said. "So residents of cities and compact communities generate less CO2 per household than people who live in more dispersed communities, like many suburbs and outlying areas."

The study shows that average transportation costs vary greatly depending on location, from a low of 14 percent of area household median income in transit-rich, compact communities, to highs of 28 percent or more in outlying areas where employment, retail, and other amenities are more dispersed.

The CNT study focused on vehicle travel as a source of emissions, since previous research shows that transportation accounts for 28 percent of all greenhouse gases in the United States.

Relying on 2007 data from the U.S. EPA National Greenhouse Gas Inventory, the report compares the conventional per-acre analysis of greenhouse gas emissions due to vehicle travel with a new per-household view in each metropolitan area studied.

The results suggest that, due to their density and transportation alternatives, cities are a central part of the climate change solution.

"If you're deciding where to live, consider moving to an urban area. You'll help fight global warming by emitting less CO2. And you're likely to drive less, so you'll spend less on transportation, saving up to $5,000 annually," Bernstein advised.

The research is an outgrowth of the center's Housing + Transportation Affordability Index, http://htaindex.cnt.org/ which examines several aspects of location efficiency such as the true cost of housing when household transportation costs are factored in.

Together, transportation and housing can account for more than 60 percent of annual household expenses for some working families living in outlying areas – significantly impacting their cost of living and quality of life, Bernstein says.

The index also shows the environmental cost of housing location, including impacts like household carbon dioxide emissions.

Since its launch a year ago, the Housing + Transportation Affordability Index has been expanded to show current CO2 maps, as well as the impact of location and gasoline costs on household budgets between the years 2000 and 2008. It has also been redesigned and enhanced for ease of use and data access.

Founded in 1978, CNT is a Chicago-based nonprofit organization that works nationally to advance urban sustainability by researching, inventing and testing strategies that use resources more efficiently and equitably. It is one of eight nonprofits to be recognized by a 2009 MacArthur Award for Creative and Effective Institutions, from the John D. and Catherine T. MacArthur Foundation.

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