Urban Form's Influence on Transportation Related Greenhouse Gas Emissions: Putting Sprawl in the Hot Seat

The Intergovernmental Panel on Climate Change has identified fossil fuel use as a significant source of greenhouse gas responsible for global warming. The primary AIM of this paper is to idendentify potential reductions in greenhouse gas emissions attributable to motorized vehicles in urban areas through the implementation of a less auto dependent -- more walkable development patterns. Data from a 6000 household travel survey collected in 1999-2000 is matched with detailed land use data in the Central Puget Sound Region. Measures of urban environments found to impact walking, driving, and transit use including density, land use mix, and street connectivity were assessed within a one kilometer street network buffer from participant residences and places of employment. Greenhouse gas emissions were estimated for each segment of each trip taken through a detailed modeling procedure sensitive to speed and distances traveled for each mode. Results show that increased levels of walkability and transit service provision are associated with significant reductions in greenhouse gas emissions when adjusting for household demographic factors and cold start emissions. Insights are provided as to the critical role of land use and transit investment in meeting long term climate change objectives.