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Two Views of Density and Driving
Are compact communities a key to fighting global warming -- or simply irrelevant?

image_preview.pngAs Lisa mentioned a few weeks back, a panel convened by the National Academy of Sciences recently concluded that compact, walkable neighborhoods can significantly reduce CO2 emissions from driving. USAToday described the findings this way:

Meeting the growing demand for conveniently located homes in neighborhoods designed to encourage walking could significantly reduce the number of miles Americans drive while giving people more housing choices, a national research panel has concluded.

The Oregonian had more:

If you want to fight global warming, one good way could be to live in a more compact neighborhood - with more neighbors and jobs close by, and where mass transit, biking and walking are accessible alternatives to the car.

But at about the same time, Technology Review ran an article summarizing a study that found the exact opposite:  "Forget Curbing Suburban Sprawl," the headline cautioned, "Building denser cities would do little to reduce CO2 emissions."

Confused?  Well, prepare to get even more confused:  the Technology Review article was covering the exact same National Academy of Sciences report as USAToday and The Oregonian. Same study, but two completely opposing interpretations.  What gives?

Well, the truth is that you can point to bits and pieces of the report that justify both perspectives. 

USA Today and the Oregonian focus on the panel's review of the academic literature -- which shows, quite clearly, that neighborhood design exerts a powerful influence on how much driving we do.  Living in a mixed-use neighborhood -- with a mixture of single family homes and multi-family housing, with some stores, transit, and other services nearby -- might cut the average person's driving by perhaps a third to a half, compared with car-dependent sprawl.  Living in an even more compact urban neighborhood, with lots of stores and jobs within walking distance, might cut per capita driving by a half to two-thirds, or perhaps more. 

image_preview.jpegAt the level of an entire metropolis, the effects of compact design can be signficant.  The report found that Portland's metropolitan land use and transportation planning system, in place since the 1970s, has cut city residents' driving by 17 percent.  Just so, residents of the comparatively compact Boston metro area drive a quarter less than do folks in sprawling Atlanta.  

And yet the study also notes that land use can't change overnight.  It's long, slow work to turn a place like Atlanta into a place like Boston. And Portland's success in reining in sprawl has been hard earned -- and even then, the reduction in gasoline use in Portland is comparable to what would be achieved by lifting average vehicle gas mileage from 20 mpg to 23 mpg. 

That's where the Technology Review's gets its pessimism.  At least one panel member went on record saying that changing land use policies was too slow, too difficult, and requires too much intergovernmental coordination, to do much to rein in greenhouse gases.

As I see it, there are at least 5 major reasons why we shouldn't settle for the more pessimistic view. 

1)  We should think on the margins:  A metro area's population might grow only a percent or two a year, so the averages don't budge much year-to-year.  But on the margins, encouraging new development in denser areas turns out to be a very effective way of reducing the greenhouse gas emissions from new residents.  Over the long haul, it's the margins that matter, since they control the direction of change.

2) There's more to emissions than how much we drive:  Reductions in driving understate the climate benefits of compact neighborhoods.  As this study shows, living in a compact neighborhood doesn't just reduce how many miles you drive, it also seems to increase the odds that you'll choose a more fuel efficient car.  And compact neighborhoods can also reduce net emissions for heating, cooling, and powering your home.

3)  Creating alternatives to sprawl has multiple benefits.  Channeling growth into compact neighborhoods can help protect farmland and open space; reduce wasteful spending on public infrastructure; promote health; reduce impervious surface per capita; and so forth.  As important as greenhouse gases are, it's only one reason among many for curbing sprawl.

4) Waiting for the feds is a sucker's game.  Cities and towns that want to take action to protect the climate simply can't sit back and wait for federal action on, say, boosting auto fuel efficiency.  Waiting for the feds is the lazy way out -- and given the ever-changing nature of politics, it's an incredibly risky strategy, since even the most progressive federal policies can change overnight.

5) Over the long haul, even small things matter--a lot. Global warming is a long-term problem, and it requires long-term solutions.  Sure, it could take 50 years or more for changes in urban form to take a major bite out of US emissions.  But if the developed world is going to make the massive emissions cuts that are going to be necessary, we're going to have to employ every single tool at our disposal.

In the end, then, I see the fatalistic view of land use -- essentially, that changing land use is just too much hard -- as not merely unhelpful, but unethical.  Rather than bemoan how hard it is to make progress, I'd rather buckle down and get to work.

This article originally appeared on Sightline Daily

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I'd add another point to your reasons why Technology Review's cynicism is misplaced: The study apparently used Portland as its model of good planning. (I haven't read it, just taken from reading this article.) Portland's great, very well-planned, don't get me wrong, but it doesn't have real density. The study should have looked at New York, San Francisco, Paris, etc. Forget 17% improvements--driving rates in New York are somewhere around 90% less than they are in other US cities. Scale matters.

Posted by: Jeremy Faludi on 29 Sep 09

Seems to me that some Americans are *still* debating merits of compact, walkable communities vs. highway-dependent sprawl. Hello? No brainer!

Posted by: Ari Tamat on 30 Sep 09

I love your reason #3, "Channeling growth into compact neighborhoods..."

Compact growth for the built environment as a means of protecting open spaces -- and even furthering the amount of undisturbed natural areas in the US -- is my number one reason for favoring dense developments over horizontal sprawl.

The infrastructure for human needs, including electric wires, sewage and water pipes, and roads, takes up far too much land area in the sprawled-development scenario, leaving little room for nature to just do its natural thing.

I'll add another reason for walkable, dense neighborhoods: cultural vibrancy. When people connect with each other face-to-face in public instead of from behind car windshields you get a richer and more connected local culture. Sprawling suburbs tend to have a cultural blandness.

Posted by: Darin on 30 Sep 09

To many Europeans, so many Americans seem to be on another planet (or so many of us wish!). [And I don't say that in the hope of provoking an unnecessarily aggressive response.]
While the report is welcome, it really is a debate long settled. Whether in village or megacity, human-scale is better for people: walking keeps you fit; bump into people eye-to-eye close to home and you make friends; having easier access to more facilities - including those who can't afford cars - builds resilient communities. The reverse of all that creates lonely paranoid slobs. Saving the environment is a bonus.
Two things really matter: a good built environment more or less *locks in* these things regardless of subsequent rhetoric, and; all savings are complementary and synergistic - 30% or more better fuel economy and 30% 'compactness' savings can both be had, and will result in spin-off benefits. Win-win-win.

Posted by: boghall on 1 Oct 09

Your reason no. 1 to press on with compact development is a good one, but there is more to the relationship between driving and compact development that is not acknowledged here, and may not have been covered by the press pieces you mention. The unfortunate dynamics of many American metropolitan areas is that trip patterns are not related to only a single urban center, but to many conjoined sub-centers. So simply increasing urban density may not have an effect on total driving unless it is specifically geared toward doing so. New residents in a downtown area may still be inclined to travel to the nearby suburb for groceries if they don't have access to the kind they want in their new neighborhood. This phenomenon actually serves to increase travel by some residents, displacing the expected gains we thought we would get from more compact development. Its not a reason to stop compact development by any means, but it is a reason to think twice about where we allot scarce resources - to development initiatives or to improvements in non-motorized travel opportunities all throughout the metropolitan region. Some of the opponents of compact development may simply be calling for the latter, which is likely to bring a quicker reduction in emissions, if done right...

Posted by: Jim on 1 Oct 09

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