Which factors matter, and why

Research tells us that CO2 from transportation is the result of a location’s accessibility to major destinations and the design characteristics of an area. Thus, both where development goes and how it is designed matter. The following neighborhood design factors have consistently been significant in predicting carbon dioxide emissions in analyses in King County. Socioeconomic variables such as income, age and auto ownership — known to affect household transportation decisions — have been taken into account.

Land-use mix and street connectivity. Both of these are associated with reduced trip distances — a mixed land-use pattern puts common destinations close to home and work, and an interconnected street network creates more direct paths between destinations. When distances get short enough, auto trips can be replaced by less polluting modes of transport such as bicycling or walking.

In our 2007 study, funded by the Washington State Department of Transportation, we found that having shops and services near workplaces, and having good conditions, influenced mode of travel to work and increased the likelihood of walking for mid-day work-based trips. In studies of employment centers in California, Robert Cervero linked an increase in land use mix at employment centers to higher shares of employees taking

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