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!!
Let’s look at those numbers a bit.
A thousands households per square mile translates into about one and a half households per acre. So going from a neighborhood designed on the post-war, upper middle class ideal—your own home on 2 private acres—to the reality in many of the Northwest’s more compact urban areas—a mixture of single family homes with small yards, together with some multifamily housing, with an average of around 10 housing units per acre—you increase density by just over 6,000 housing units per acre.
And, 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.
So if Brownstone and Golob are even close to being correct, the kind of neighborhood you choose has a tremendous influence on your total gas consumption, and the overall impact of your daily driving on the climate. And their findings argue that one way to reduce fuel consumption is to encourage new development in compact neighborhoods.
This, of course, is just one study among many. There are some researchers who find that the relationship between density and driving is far more tenuous. Still, these sorts of results are what keep me searching for that white whale. (It’s there…I know it…)