WSDOT quantifies the GHG reduction impact of sidewalk coverage.

“If you build it, they will come” seems to hold for building sidewalks. A recent report for the Washington State Department of Transportation found that increasing sidewalk coverage from 30 percent to 70 percent of all streets was estimated to reduce VMT by 3.4 percent and GHG emissions by 4.9 percent.

The report, An Assessment of Urban Form and Pedestrian and Transit Improvements as an Integrated GHG Reduction Strategy, is one of the first to examine the relationship between sidewalk coverage, vehicle miles traveled (VMT), and greenhouse gas (GHG) emissions. Using travel data from the 2006 PSRC Household Activity Survey, a 2-day travel survey conducted in the 4-county Puget Sound Region, the report also examines the impact of land use, transit, and parking cost on VMT and GHG emissions.

Not surprisingly, parking cost was found to have the highest impact on VMT and GHG emissions—increasing parking costs from $0.28 per hour to $1.19 per hour (50th to 75th percentile) resulted in an 11.5 percent decline in VMT and a 9.9 percent decline in GHG emissions. Land use mix was also found to be a significant factor in VMT and GHG emissions. However, the report’s most notable finding is that sidewalk coverage is a significant factor in reducing GHG emissions and is associated with reductions in VMT as well.

This research presents a first step in estimating the VMT/GHG reduction benefits of sidewalks; however it is was hindered the fact that the analysis was limited to the nine most populated cities in King County, WA. Local sidewalk data layers required for the analysis were unavailable in other areas of the Puget Sound Region. As additional geospatial sidewalk data is made available, reflecting a greater diversity of communities, new research will be more able to quantify the impacts of sidewalk coverage on travel patterns.