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 Inhabitat.com 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.

  • DJB

    There’s a similar study called “Environmental Characteristics of Smart Growth Neighborhoods – Phase II: Two Nashville Neighborhoods” published by the NRDC in 2003. It compares a denser inner-ring suburb of Nashville with a more diffuse outer-ring suburb of Nashville.

    The study controlled for household size, auto ownership, and trip making rates (but income data for the specific areas of analysis were unavailable). Both neighborhoods lacked transit service.

    The result: on a per-capita basis the denser, more centrally-located suburb consumed 1/3 less land (former habitat), 13% less water, produced 7% less vehicular air pollution and 25% less vehicular carbon dioxide.

  • BOB2

    The research is pretty conclusive on VMT and density. And, most models that are used for transportation planning exagerate the growth in suburban traffic, by the use of linear forecasting that show eternal growth in vehicle miles traveled (VMT) into the future, which implies the need for more freeways. This was the case in Orange County, but in the late 80’s and 90’s as density rose in the OC, census data and survey data showed that per capita VMT actually fell???

    The casality for this is 1) what I have called the Wall Mart-Home Depot effect–as density increases, more retail and jobs are also added, reducing the required travel distances to goods and services. And, 2) the self limiting effects of congestion on the utility of travel, which are underestimated. Our erroneous travel demand models assume, based on linear analysis that as speeds and utility of travel falls, consumption continues to grow (forever).

    Unless we are somehow making days longer, utility of travel must fall as a function of constrained time. As trip times increase, the cost rises and utility falls, constrained by the time available and allocated for trip making. This fallacy persists despite the fact that it is also against the most basic understanding of economics to assert that as utility falls consumption will continue to grow.

    How ludicrous is this flawed thinking? SCAG once showed that people would travel in congested conditions from their Palmdale homes to the LA basin jobs-taking 8 hours on the road-working 8 hours-then driving back in traffic for 8 hours. It is, of course, pure nonsense, but was part of the analysis they continued to use (and still use) to recommend additional road capacity.