Connecting Residential Density and Fuel Consumption

Sometimes, and with some people, intuitive arguments just don’t cut it. It’s good to have some facts and figures at hand. That’s the topic of today’s featured post from the Streetsblog Network. On member site Worldchanging, Clark Williams-Derry wrote:

10326_largearticlephoto.jpgPhoto of a neighborhood in Ventura, California, by -Wink- via Flickr.

Sometimes I feel a little like Captain Ahab, forever in search of an elusive white whale. In my case, though, the whale is profoundly geeky: I’m in search of a definitive study, or set of studies, showing
the relationship between urban design and transportation habits — particularly, how neighborhood design affects fuel use.
So far, that particular white whale remains elusive — but searching for it turns up all sorts of interesting tidbits. Like this one:
University of California researchers David Brownstone and Thomas Golob have looked at the relationship between residential density and driving habits, and concluded that:

"Comparing two California households that are similar in all respects except residential density, a lower density of 1,000 housing units per
square mile…implies an increase of 1,200 miles driven per year…and 65 more gallons of fuel used per household."

Thar she blows!!

…according to the numbers that these authors have crunched, living in a compact neighborhood rather than a sprawling exurb would lead to a decline in gasoline consumption of…wait for it…395 gallons of gasoline per household per year!

That’s a lot of gas.  By comparison, the average resident of the Northwest states consumes about 390 gallons per year; so living in a denser neighborhood does as much to reduce your driving as having one fewer person in your household.

Which brings us to the question of designing that density.

Dwell magazine and are currently sponsoring a competition called Reburbia, "dedicated to re-envisioning the suburbs." Streetsblog Network member BLDG Blog is one of the judges who narrowed down the contest to 20 finalists. Reader votes will decide the winner, so head on over and see if you can find an appealing, fuel-efficient template for the American future.

Speaking of contests, it’s not too late to enter the American Public Transportation Association’s "Dump the Pump" contest. APTA is looking for videos of people explaining why they’re ditching their cars in favor of transit, and the deadline is September 18. The top prize is a year of free public transportation and an iPod Touch.

Also on the network today, Making Places looks at what we can learn from the Dutch concept of "self-explaining" roads. Among the lessons: "Wider, straighter, faster" does not mean safer.

  • Adam

    I wrote my grad school thesis on that topic. I worked with the State of MA to look at the relationship between density and VMT. We used GIS-based models to match housing/job densities to VMT predictions based on travel patterns. I found that doubling housing density is associated with a 25 percent reduction in VMT, and doubling job density is associated with a 10 percent reduction in VMT. Read the whole thing here:

  • Kate

    I also wrote my grad school thesis on a similar topic. What I found that often gets left out of these discussions is that density is an important factor, but the mix of uses is equally or more important. When you’re talking about how much you drive, it depends on how far the destinations are. In older Northeast cities, smaller grocery stores, shops, schools, etc are scattered throughout the neighborhoods, making trips shorter. L.A. is incredibly dense, more dense than Cambridge, but it’s much easier in Cambridge to choose to walk up the street to the store rather than drive. Simply promoting residential density won’t change the environmental impact of suburbs as much as mixed used zoning could.

  • And I would add that regional accessibility is perhaps the most important factor that has been studied. Regional accessibility (which measures the distance or travel time between a given location and other important locations/destinations within a metro region) is often associated with neighborhood density, mixed use, transit access, and walkability, so many studies do not segregate the various factors. But those that do (Ewing, Cervero, Walters, etc.) find all five to be individually significant.

    The study cited here and on WorldChanging actually concluded that the effect of density was not sufficiently large to be effective as a policy tool (and used some very dated data to make the point). That is probably true with respect to density alone (imagine a pod of high-rises in an outlying greenfield). But density and mixed use coupled with transit, walkability and, especially, a good relatively central location, can be quite powerful.