SSTI research highlights built environment policies to reduce VMT

By Bill Holloway

As part of a larger 2015 project for the Commonwealth of Massachusetts, SSTI investigated the influence of six built environment variables on passenger vehicle miles traveled. Using data on average daily household VMT at the Census block group level from the Massachusetts Registry of Motor Vehicles, along with detailed land use data and transportation system information, we were able to determine how VMT varied according to the following variables:

  1. Land use mix (average distance between homes and the nearest retail establishment)
  2. Household density (households per square mile of land area)
  3. Sidewalk coverage (percentage of road miles with a sidewalk at least 3 feet in width)
  4. Transit access (average distance between homes and the nearest transit stop)
  5. Intersection density (number of intersections per square mile)
  6. Managed parking (block groups with a single-use parking structure within 1 mile scored 1, others scored 0)

As shown in the figure below, daily household VMT varies dramatically across the state, with urban areas exhibiting the lowest VMT and rural areas the highest.MassVMT map

After determining the relationship between the variables and VMT, we estimated VMT growth through 2040 under business-as-usual (BAU) conditions, and developed and evaluated the impacts of a variety of potential policies to reduce VMT growth over the coming years. The only policy options expected to reduce 2040 passenger VMT below 2010 levels involved changes to all six variables. However, policies that adjust only a single variable could also make a significant difference. Increasing land use mix—i.e., reducing the distance between homes and retail establishments—would be expected to reduce VMT by 4.3 percent compared to BAU, the largest impact of any single built environment policy. Increasing sidewalk coverage would be expected to reduce VMT by 3.5 percent.

The full paper, which was presented at the 96th TRB Annual Meeting in January, can be downloaded here.

Bill Holloway was a Transportation Policy Analyst at SSTI until Feb 10. We wish him well in his new position at the Madison Area MPO.