A study published in the Journal of Urban Economics uses a model that combines residential density, driving and gasoline consumption that confirms something that most of us already suspect: sprawl means fewer transportation choices, more time sitting in our cars, more of our incomes spent on gas, and less time for other, more important stuff like family and friends.
So, even if it’s true that people in areas that are sprawling really do tend to roll in bigger, less fuel efficient rides, it’s not just about personal choices (good or bad). More sprawl means more driving and more gasoline use and when school, the grocery store and work are miles away from each other the only sensible thing to do is drive. Unfortunately, short of where we live, many “choices” are made for us by the built environment.
The study models a comparison of housing units that are alike except for their location. One’s in a low density area (sprawl) and the other in an area with more housing units per mile (not sprawl). (The data used for their model is drawn from the National Household Transportation Survey.) Lo and behold, housing units located in areas of low density lead to 1,200 more miles traveled and 65 more gallons of fuel use than units in higher density areas. Here is a table that details the numbers:
The study found that two things account for the additional fuel use in low density areas are more driving and vehicle choice. “Increased mileage leads to a difference of 45 gallons, but there is a direct effect of density through lower fleet fuel economy of 20 gallons per year,” says the study.
So, basically, Knute Berger has part of it right in his piece on Seattle’s apparent “moral obsession” with being sustainable. Suburbanites tend to have bigger cars that guzzle more gas (there’s a reason they call those big honkers ‘Suburbans’.) But the study shows this isn’t only a question of the choices city people make versus the ones suburban folks make, but also one of good land use planning.
What makes this study interesting and useful is that it looks at VMT, gasoline and land use together to quantitatively confirm what seems obvious. Our local and regional land use decisions do have an impact on fuel consumption. Berger’s article implies that our relationship between driving, cars and sustainability is a moral one based completely on good or bad personal choices. That just isn’t the case.
Driving and sprawl are largely systemic issues not moral personal choices. If local and regional government support land use patterns that encourage density for future development, people will drive less because they won’t need to—because better choices will be available. Land use policies are transportation policies. And how we organize ourselves can support convenience and sustainability. And that means less driving and less consumption of gasoline—good for quality of life and for our pocketbooks.