There are several financial and environmental costs associated with roads, including:
Pollution from stormwater runoff, including oil, brake dust, and other vehicle-related pollutants
Cost of building roads, which is passed from developers to home buyers
Ongoing cost of maintaining roads, which is paid by municipalities and residents
Minimizing the length of road built in new subdivisions, and the width of roads, can reduce these costs.
What are we measuring?
Acres of new right-of-way per home in approved residential subdivisions.
Over the last 3 decades, the amount of area used for right-of-way in residential subdivisions has decreased by over 40% on a per-home basis. In part, this is due to a greater proportion of new subdivisions located in urban areas where density — the number of homes per acre — is higher than in the rural areas. In rural areas, the amount of impervious area per home has been fairly variable. This indicator is influenced by two primary factors:
Residential Density — the number of homes divided by the area of the subdivision.
Street Width — which translates to the amount of land placed into the subdivision’s right-of-way, or the area set aside for the street, sidewalks, and planter strip.
Subdivisions are typically divided into right-of-way, residential lots, and open space. As shown in the example, the right-of-way includes the street, sidewalks, planter strip (the area between the street and sidewalk), and an additional area behind the sidewalk. Not all of the right-of-way is impervious. There are 26 residential lots within this subdivision, plus open space tracts (which include stormwater facilities) in the bottom right corner of the image.