Does smart growth reduce carbon emissions? Bet the house on it.
The National Association of Home Builders would have us believe that development patterns have nothing to do with carbon emissions. But the research paints a dramatically different picture.
There’s a compelling graph in researcher Todd Litman’s article in the Spring 2011 Center for Real Estate Quarterly, a publication of Portland State University in Portland, Oregon.
Attached at top right, the graph shows vehicle miles traveled (VMT) in three types of neighborhoods in Portland. Neighborhoods with good transit and mixed use average 9.8 VMT/household/day. Neighborhoods with good transit but no mix of uses average 13.3 VMT/household/day. The rest of the region, with no mix of uses or good transit — mostly characterized by suburban sprawl — averages 21.8 VMT/household/day.
This difference — 55 percent less automobile use in mixed-use, transit-served neighborhoods compared to sprawl — is dramatic.
In his article, “Can Smart Growth policies conserve energy and reduce emissions,” Litman explains why people drive so much less in compact urban places. “In multi-modal, smart growth locations residents tend to own fewer vehicles, drive fewer annual miles, and rely more on alternative modes. Even larger vehicle travel reductions occur where smart growth is implemented with efficient road, parking and fuel pricing; such pricing reforms tend to be more effective (price elasticities increase) at reducing vehicle travel if travelers have viable alternatives.”
Is this just a quirk of the Portland area, the planners' utopia with an urban growth boundary and an extensive light rail system? Thankfully, The Center for Neighborhood Technology (CNT) has mapped VMT and greenhouse gas emissions from automobile use across the US. The map for Portland is shown at upper right. Below that, you can see the map for Pittsburgh. Notice any similarity? It’s the same pattern.
Drill down a little more on this interactive site, and the differences become even clearer. In Pittsburgh, for example, the close-in city neighborhoods range from 7,000 to 11,000 VMT/household/year, while the distant suburbs range from 21,000 to 25,000 VMT/household/year. The same general pattern holds for literally every metro region. Without exception. You can see it with your own eyes; just go to the site, click on a region, and select the variables "CO2 per household" and "VMT per household."
The National Association of Home Builders (NAHB) would have us believe that this is all a coincidence. “The existing body of research demonstrates no clear link between residential land use and greenhouse gas emissions and leaves tremendous uncertainty as to the interplay of those factors,” NAHB writes in Climate Change, Density and Development, published early in 2011.
NAHB relies on papers that it has funded by consultants like Eric Fruits of Economics International. In a recent article for The Center for Real Estate Quarterly, Fruits concedes: “On its face, the linkage between compact development and greenhouse gas emissions seems obvious: (1) if individuals drive less, then vehicle emissions will decline, and (2) if families live in more compact developments, then they would likely drive less and use less energy, and therefore (3) compact development would reduce greenhouse gas emissions.”
Well, yeah, when this pattern holds for every Metro area in the US, that would seem obvious. But notice, also, that Fruits reduces smart growth to one characteristic: “compact,” or density.
Having isolated one variable, Fruits performs his own analysis of the research, and comes to the conclusion that the “available data indicate that the connections are weak, bordering on non-existent,” between density and greenhouse gas emissions.
Litman cites studies that show density alone does in fact have “modest impacts” on VMT and greenhouse gases. But the big impacts from smart growth are from a series of related characteristics — street connectivity, mixed-use, availability of transit, thoroughfare design, and effective parking management among them — that are also correlated with reductions in VMT.
In other words, if all you do is bring people closer together, you get modest reductions in gasoline consumption. But if you do all of the other things associated with smart growth — that is to say, create a walkable environment with multiple destinations and alternative modes of transportation — the impacts on VMT, energy use, and greenhouse gas emissions are huge. It’s worth glancing at Litman’s table, “Land use impacts on travel,” attached here, which is a summary of research on how various smart growth strategies affect automobile use.
The overwhelming evidence from the research, therefore, confirms what we see with our own eyes in, once again, every metro area in the US.
Why is NAHB denying this? Calvert Asset Management Company, an investment fund based in Bethesda, Maryland, released a report in December, 2010, on how the 10 largest publicly held homebuilding firms in the US are doing on sustainability.
The verdict: Most of them fare poorly. While their record on home energy use is merely poor, their performance on land-use practices is dismal, Calvert notes. Six of the 10 builders got a score of zero out of a 100 in this category, and the other four all scored under 20.
To sum it up: the 10 largest homebuilders have a dismal record on sustainable land-use policies, and the national organization, NAHB, is in denial about how land use affects global warming.
Now, it’s time to ask the home builders: How’s that working out for you?
The industry is in deep depression, with new home sales at their lowest level since records have been kept in a half century. Many of the leading homebuilders are losing money hand over foot. And solid research indicates that the market for large-lot single-family housing, the homebuilders bread-and-butter for 60 years, is not coming back for at least another decade.
It also happens to be that large-lot single-family housing is the type that generates the worst greenhouse gas emissions.
Furthermore, research also indicates that the same housing that produces fewer greenhouse gases — transit-oriented, compact development — is also the kind that is likely to be more successful for decades to come.
I know that the summer beach season is almost upon us, but even so, it’s time for the NAHB, and the major builders, to pull their heads out of the sand.
Download Litman's and Fruits's papers at the Center for Real Estate Quarterly.
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Comments
Carbon
This all may be a non debateable subject since there is a growing body of evidence that man made carbon emmissions have almost nothing to do with climate changes.
There are plenty of other good reasons to promote smart growth without bringing in the greenhouse gas effect. We should stick with those.
You are an idiot
@William Dempsey
There is no "body of evidence that man made carbon emmissions have almost nothing to do with climate changes". There may be a growing body of BS generated by climate science deniers(though they mostly just repeat and rehash the same things over and over). However, most of that can be easily debunked(and has been if you bother to look) and is far far outweighed by the evidence in favor of carbon emissions effect on climate. You're either a sucker and have a financial stake in spreading these lies.
Strawman
I followed your link to the NAHB report and - you're right - the whole thing is the classic straw man argument. First, they characterize the "prevailing beliefs within the planning community" as saying density alone will solve climate change, and then they present themselves as the more nuanced and data-driven alternative in opposing this claim. "Solutions that seem
simple to some are instead complex," they say. ok, sure.
Then the report states that government "cannot address climate change to the exclusion of other crucial concerns." Who is saying it should? Another strawman.
Instead of wondering how density interacts with other factors (diversity, design, etc.), they take the relatively modest effect it alone has on GHG emissions to mean that it's just no biggie and should not be taken into account in policy decisions - at least that's the implication.
If there's any one source "in the planning community" that represents the current state of research on the effects of land use on VMT and mode choice, it's Robert Cervaro's meta-analysis from last summer in the Journal of the American Planning Association. This study attempted to tease apart the complex factors that influence travel behavior, and showed that neighborhood-scaled residential density is one factor among many (and not the most important) that have a positive correlation with a more efficient transportation system. Distance to the Central Business District (a.k.a "regional density") and intersection density were more important, but they all interact with eachother in - yes - complex ways that create a whole greater than the sum of its parts.
My guess is the researchers commissioned for this study know all of this, but NAHB framed the scope and spun the results in such a way to prove their own point.
I call "Biostitutes!"
@Mr. Dempsey: No, there is *not* a "growing body of evidence" that man-made emissions have almost nothing to do with climate change, unless, of course, you count Exxon's desperate propaganda.<br>
For example, reports like <a href="http://www.treehugger.com/files/2011/05/climate-skeptic-debunked-report-exposes-denial-indsutry.php">this</a> one debunk the efforts of such climate-change skeptics, and disclose just how much funding the likes of Exxon provides to promote confusion.<br>
Nevertheless, I'll agree that climate change is not the only reason to embrace New Urbanism. Never mind the "dueling experts" about climate instability, and its source in human activity...There's another argument with exactly the same remedy that is not disputed, even by the American Petroleum Institute (the API is the oil lobby): U.S. peak oil. <br>
Oil production for a single field, or a collection of oil fields, conforms roughly to a bell-shaped curve. Uncontroversially, U.S. domestic oil production <a href="http://www.theoildrum.com/node/5969">peaked</a> about 40 years ago. The price of a barrel of oil in 1971: <$2. Now: $80 - $140. Amount of oil imported in 1971: 30%. Now: 50% - 70%. Notice a trend?<br>
Again, the API will tell you that no amount of drilling offshore or in Alaska's National Wildlife Refuge will return us to peak production. And that peak was predicted because domestic oil discoveries peaked roughly 40 years before the production peak. Guess when discoveries peaked worldwide? About 40 years ago. <br>
So there's a perfectly understandable reluctance from the likes of Exxon when it comes to exploring and/or promoting alternatives to petroleum, but must we always be slaves of the oil companies' propaganda? Is that really in the public's interest?<br>
Other variables
As a private sector planner, I am genuinely interested in this topic, but find most of the reporting on research (if not the research itself) to be agenda driven. Do either of these studies account for other variables such as income, age, family status and employment location? Isn't it entirely possible that some people self select the neighborhoods that best fit their life situation? Does it necessarily follow that if you transport a suburban family into a compact downtown neighborhood that their lifestyle and driving behavior will become that of today's typical downtown resident?
Self selection
To the extent that they are able to, certainly people select the neighborhoods that best fit their life and and aspirations. But due to decades of planning and zoning for auto-oriented development, there is a shortage of mixed-use, walkable neighborhoods, especially in the suburbs, where many jobs are located. A lot of people who would prefer to live in walkable neighborhoods find themselves locating in drivable suburbs. When they do that, they drive more than they would prefer or they suffer with lack of mobility. Neither is a good outcome.
variables, NAHB, etc
First, Mr. Shattuck: There are various studies that address the precise questions you have. I am also a planner and I read voraciously because there is a mountain of new and changing information about planning. Being voracious has the unfortunate side effect of not being able to readily point to the article I'm thinking of. I believe Todd Litman looked at that question, and Susan Handy might also have done so. The short answer is, yes, suburban-oriented families' behavior also changes, although not as much as the behavior of an urban-oriented family. See http://scholar.google.com and you'll turn up at least two papers.
Mr. Dempsey: the "argument" about climate change and its genesis has long been settled. Since the early 1990s. I studied the general subject in the 1980s as an undergraduate and thus followed the professional discussion with great interest. However, in the interest of tying up important resources in a fruitless debate with dishonest players, I agree that we should move on, understand that whatever its genesis western culture contributes to the problem, and go about finding solutions in order that our species might continue to prosper. Do you have children? I presume you care whether they have a future and how bright it might or might not be?
NAHB: Oh, for pity's sake. The market, the financials, and the demographics have changed, but they still cling to their outdated model of development. I don't ever again want anyone telling me how wise "the market" is or the "development community." Anyone who dares do so is invited to come to the northern San Joaquin Valley and revisit those patently ridiculous notions.
Rob, you rock. Thank you always for your thoughtful posts.
Correction
In paragraph 5, I changed the text to say VMT/household/year, not VMT/household/day. Sorry for the confusion.
self-selection bias
Mr. Shattuck, most of the studies referenced in Cervero's paper do control for those things you mentioned (and he let's us know when they don't). I agree with you that the self-selection problem is really trickier though, and I don't know if there is a great way to figure that out whether someone who would drive less anyway chooses to live in a compact area or not. I guess surveying would help, but there's problems with that too.
But I'm not too bothered by self-selection bias, for all practical purposes. Even if the kinds of people choosing to live in compact areas already want to drive less, there still has to be enough urban areas in existence to meet this demand. Otherwise, you may end up with folks who would self-select a compact area, and thus drive less, but just can't for lack of availability/affordability. Whether the compact form itself influences behavior or the compact form allows people to express the behavorior they already desire, the message is the same: build more compact places.
TRB report: Compact development reduces VMT.
In 2009, the Transportation Research Board released a final report from a commission on which I served, along with other academics and practitioners. Reviewing all the best available research from the U.S. alone, we concluded that compact, mixed-use development can reduce driving and thereby contribute to lower levels transportation-related GHG emissions. Evidence we reviewed confirms that selection bias matters. But in the most careful (and usually that means the most restrictive) studies, even after correction for selection, there are still non-trivial differences in travel behavior between those living in dense, mixed, and transit-rich areas, on the one hand, and those living in low-density, separate-use, auto-dependent areas, on the other. More explicitly: compact development doesn't just attract people who want to drive less; it also reduces driving among those who would otherwise drive more.
This is important to the extent that only a small share of housing consumers (perhaps 30% to 40% at most?) have strong underlying preferences for low-VMT built environments. If "building to the market" is the only rationale for providing compact development, and if we expect no further VMT reduction from compactness beyond that predicted by previous preferences for driving, then compact development won't yield a great difference in GHG emissions. If, on the other hand, compactness shapes preferences, then it has more chance of contributing to GHG reductions.
See http://www.trb.org/Publications/Blurbs/Driving_and_the_Built_Environment_Effects_of_Compa_162093.aspx
for more on the TRB report. The panel agreed unanimously that development patterns matter for VMT, but disagreed on the degree to which elected officials and others will accept and accommodate the scale of change in development patterns to make an appreciable difference in GHG emissions. We did not, however, review evidence on what factors associate with political acceptability of more compact development patterns.
On a side note: four excellent chapters in the brand-new book "Auto Motives: Understanding Car Use Behaviours" (Lucas, Blumenberg, and Weinberger, eds.) probe deeply into the factors that lead to people's choices for using cars, including (for example) built environment, past experience, and peer pressure.
One last word: none of this takes into account the non-VMT related reductions in GHG that can be provided by more compact development patterns, ranging from district heating and cooling to reduction of the loss of carbon sinks (forest, wetlands, etc.).
Rolf
non-VMT effects of smart growth on GHGs?
@Rolf Pendall: "non-VMT related reductions in GHG that can be provided by more compact development patterns, ranging from district heating and cooling to reduction of the loss of carbon sinks (forest, wetlands, etc.)."
Below (with same Subject:) I ask for more information on this topic. Unfortunately I skipped this part of your post :-(
VMT vs. Carbon Emissions
Where will this conversation go when we move to zero emission vehicles? Is VMT the issue, or is it the various pollutants it causes? From my point of view, VMT in itself is neither good nor bad.
Thanks!
Thanks Robert for your excellent summary of this issue.
For more information on the ways that various land use factors affect travel activity see my report, Land Use Impacts On Transport: How Land Use Factors Affect Travel Behavior, (www.vtpi.org/landtravel.pdf ), which summarizes the literature, including discussion of self-selection.
I agree that it is a mistake to justify smart growth and other vehicle travel reduction strategies just on their climate change emission reduction benefits. There are many other economic, social and environmental benefits to consider. For information see, Understanding Smart Growth Savings: What We Know About Public Infrastructure and Service Cost Savings (www.vtpi.org/sg_save.pdf ) and Evaluating Criticism of Smart Growth (www.vtpi.org/sgcritics.pdf ).
There is also good evidence that current demographic and economic trends are increasing demand for smart growth locations, as discussed in, Where We Want To Be: Household Location Preferences And Their Implications For Smart Growth, ( www.vtpi.org/sgcp.pdf ). This suggests that land use and transport policy reforms that support smart growth (reduced and more flexible parking requirements, allowing more mixed housing types and land uses, improvements to walking, cycling and public transit, etc.) are needed to allow new development to better respond to future consumer preferences.
Unplanning – Livable Cities and Political Choices
Have you guys read Charles Siegels last book Unplanning – Livable Cities and Political Choices? It's downloadable for free HERE!
Also the whole point of modernism is Disconnection from Life!
"James Howard Kunstler believes that our suburban sprawl is unsustainable, and will have to be abandoned with the end of cheap oil. In his nightmare scenario of societal breakdown, there is no more state structure capable of maintaining law and order, let alone enforcing these stupid urban codes. Do we have to come to that point to substitute the codes on the books today with city-regenerating codes? Illegal or not, people will eventually have to abandon those codes and replace them with New Urbanist codes." - From Nikos A. Salingaros last book, Twelve Lectures On Architecture, page 203.
@ Todd Litman
Todd Litman, your research is impressive! I've added them all for further reading of my own small article about the spread of suburbia here I live, here.
I've also recommended them at the blogg of the Norwegian Professor Erling Holden, which work in the same field as you. I should be happy if you could contact him and supporting him with your research, as there is NO sagn of New Urbanism yet in Norway.
Kind regards,
Øyvind Holmstad
excellent commentary, Rob
One clarification:
You wrote:
"Litman cites studies that show density alone does in fact have “modest impacts” on VMT and greenhouse gases. But the big impacts from smart growth are from a series of related characteristics — street connectivity, mixed-use, availability of transit, thoroughfare design, and effective parking management among them — that are also correlated with reductions in VMT."
Absolutely true. But you omitted the most important factor of all, which is regional accessibilty (sometimes called "destination" accessibility), or the location of a place within a region. The more central a place is to the region, or to a strong suburban center, the lower the VMT, in large (though not exclusive) part because driving distances are shorter. In Ewing and Cervero's exhaustive study of the published literature (http://bit.ly/bWYVQq), they found that such locations can be almost as significant in reducing driving rates as other significant factors (e.g., street connectivity, neighborhood density, mixed land use, street design) combined. This is why smart growth favors infill and redevelopment and disfavors new greenfield development on the fringe of a region. It is also a principal (though not the only) reason why those CO2 maps show such lower emissions rates in the centers of regions.
Street connectivity, by the way, is the strongest indicator of how much walking takes place in a neighborhood.
Air Quality
While I believe there is a link between carbon emmissions and climate change, until that argument is settled I am more concerned about air quality. Fewer vehicle trips equals better air to breathe, especially if you are close to a highway or an arterial street.
non-VMT effects of smart growth on GHGs?
Great stuff, but of course limiting VMTs is not the only way smart growth limits GHG emissions. I'm wondering (quite strongly--I'm looking for graduate programs where I could learn to model this and related problems) if anyone is looking at non-transportational effects such as:
I'm guessing non-transportational effects are not so strong in the US (outside of, e.g., NYC) but could be significant in Europe and other places where cogeneration is more widespread.
fwiw, Tom Roche [Tom_Roche at pobox dot com]
Late response to Rolf
Rolf, thanks for your well-informed post. I would just respond to this part:
>>This is important to the extent that only a small share of housing consumers (perhaps 30% to 40% at most?) have strong underlying preferences for low-VMT built environments. If "building to the market" is the only rationale for providing compact development, and if we expect no further VMT reduction from compactness beyond that predicted by previous preferences for driving, then compact development won't yield a great difference in GHG emissions. If, on the other hand, compactness shapes preferences, then it has more chance of contributing to GHG reductions.<<
There are two factors that change the market outlook. As ULI, Prof. Arthur Nelson and others have shown, there is a vast oversupply of large-lot single family housing on the market right now, and an undersupply of multifamily and small lot housing.
The second factor is that the change in the housing market is really where the demand comes from, and that change has shifted towards the kind of people who would tend to prefer more urban housing types.
While I think you are right that compactness shapes preferences, I also think that market would take us a long way toward compactness if there was anything close to a level playing field in regulations and infrastructure.
Here's two links: http://newurbannetwork.com/news-opinion/blogs/robert-steuteville/14629/housing-irresistible-force-meets-immovable-object
http://newurbannetwork.com/news-opinion/blogs/robert-steuteville/14620/coming-housing-calamity
VMT Matters
Claire says VMT is neither good nor bad.
VMT matters regardless how we fuel our cars. VMT will determine how much land is needed to move and store vehicles; how much will need to be invested/spent to build and maintain road and parking infrastructure and the demand for energy. For example if we switched to all electric cars how much additional electricity would we need to generate to operate these vehicles?