Category Archives: Suburbia

In 40 years, will self-driving cars send us packing for the suburbs?


At the end of 2013, the journal Cityscape put the following statement to contributors and asked their opinion of it: “In 40 years, the average person will live closer to her neighbors and farther from the ground than she does today.” This is a critique of one response. More to come…

Most urbanists will tell you that we’ll be living at higher densities sooner than you think. Nathaniel Baum-Snow, an economist at Brown University, is one of them. He cites a handful of reasons why he thinks we’ll all be living closer to our neighbors 40 years from now, including commute times, declining fertility rates, and stalled highway construction. Baum-Snow makes valid points, but many of his assumptions presume that the world 40 years from now, at least technologically, will look similar to today. Given the last 40 years, I’ll be surprised if that happens.

Self-driving cars are one of the biggest threats to the future of cities, and widespread adoption could single-handedly undermine one of Baum-Snow’s most compelling arguments—commute times, which he says will be a driving force behind increasing urban densities. As incomes have risen for many city dwellers—those in the top 50 percent, at least—the value of their commute time has also risen. Given Marchetti’s constant, which says that commute times tend to hover around 30 minutes each way, snarled traffic will force the wealthy out of the suburbs and back to cities. In a sense, we’ve already started to see that.

But self-driving cars could reverse that trend. As people’s commutes are freed up for other tasks, including work, they’ll stretch their daily trips, once again allowing them to live where they want. And as we’ve seen, people want to live where they have more space.¹ Compounding the problem is the fact that most early adopters are likely to be wealthy, the same people Baum-Snow says will be looking to drive less.

Working in cities’ favor, Baum-Snow adds, are declining fertility rates. Between 1967 and today, birth rates have fallen from 0.122 births per woman of childbearing age to 0.065, nearly a 50 percent drop. With people having half as many children, the need for space should decline. But as we’ve seen, that’s not necessarily the case. Between 1973 and 2012, median home sizes have grown from 1,525 square feet to 2,306 square feet, the same time that fertility was declining. In that same time period, median household income has risen almost $10,000 when adjusted for inflation, a nearly 25 percent increase.²

Then there’s the siren song of the suburbs—school quality. Suburban and small town school districts frequently outperform their urban counterparts. Baum-Snow notes that the quality of public schools in big cities has stabilized, at least, but that isn’t quite the same as improving. Plus, even if they do improve, urban schools will have to overcome the stereotype wrought by decades of poor performance.

(There is a simple fix, of course—invest in public education at all levels. Early childhood programs have shown great promise at preparing children of all backgrounds for full-time school, and education is the best chance many of children have to break free of poverty.)

Given these realities, I don’t think the future points to downtown, as Baum-Snow does. It’s true that city centers are the hot place to be, but density numbers don’t reflect the newfound enthusiasm. And trends in technology could shatter the many cities’ recoveries.

Despite that, I think many of us—at least, those of us not in the top few percent—will be living closer together. Not downtown, but in the sprawling inner suburbs that will be indistinguishable from the rest of the city, slogging through long commutes between home—which was convenient to the old job we got laid off from—and our new jobs on the wrong side of town.

  1. Home sizes briefly halted their inflation during the recession, but they’ve started to rise again.
  2. On top of that, interest rates are lower today than in the 1970s. That could change 40 years from now, of course.

Photo by Michael Colburn.


Baum-Snow, Nathaniel. 2013. “Changes in Urban Population Densities Over the Next 40 Years.” Cityscape 15(3).

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Marchetti’s constant, or why the 30 minute commute is here to stay

Population density fostered literacy, the Industrial Revolution

Your carbon footprint may not be as low as you think

Tokyo buildings

High-density living—it’s an urbanist’s answer to climate change. Living close is a straightforward solution to a complex problem. One that’s probably a little too simplistic. While living in dense cities certainly does reduce your carbon footprint, the results may not be as dramatic as you suspect.

That’s according to a new research paper by Chris Jones and Dan Kammen, two University of California, Berkeley researchers who have extensively studied people’s carbon footprints. Their results show that moving from a carbon-heavy suburb to an ultra-dense city will only reduce your emissions by 35 percent on average. Yes, that’s a big number, but perhaps not as significant as we’re often led to believe. But fortunately lurking within their data is an even simpler—and maybe even more effective—way for metro areas to reduce their footprint.

Jones and Kammen have spent years honing their methodology for determining people’s carbon footprints. Jones is the lead scientist at the Renewable and Appropriate Energy Lab and Kammen is its director and a professor at the university. Together they’ve created one of the most detailed and accurate carbon footprint calculators available online. To develop that tool, they had to ask a lot of people a lot of questions about their lifestyles. With that experience, they’ve published a number of papers that lift the veil on our energy use, revealing which aspects of our lives produce the most greenhouse gas emissions.

Their latest paper is contains some seemingly unexpected results, all gleaned by modeling emissions for individual ZIP codes. For example, you might expect carbon footprint to fall commensurately with population density. After all, living in the boonies makes you pretty reliant on cars while living in the city frees you to take transit. But it isn’t so clear cut. People living far from cities and suburbs have fewer destinations and tend to buy less, driving down their overall footprint.

As population density increases, then, household carbon footprints rise initially, up to 3,000 people per square mile. After that point, emissions per household drop, though the trend isn’t linear, it’s logarithmic, which is to say it falls fast at first but then with plateaus.

Jones and Kammen found that the most carbon intensive places to live are about 15 to 45 miles from the center of the nearest major city.¹ Most households in these bands have higher incomes and more members, both of which are tightly coupled with carbon emissions in the U.S. Those households also have higher transportation footprints—50 percent more than city center households. Overall, suburbs account for half of the U.S.’s carbon footprint. Large cities contribute 30 percent.

No city can escape its suburbs. As long as people have the means and the desire, they’ll live in those sorts of places. So to reduce a metro area’s overall carbon footprint, Jones and Kammen say, you have to tailor solutions that will work for each region of the country and each part of the metro. To be successful, those solutions must work with people’s existing behaviors.

Take the suburbs, for example. “These locations are ideal candidates for a combination of energy efficient technologies, including whole home energy upgrades and solar photovoltaic systems combined with electric vehicles,” they write. Forcing someone to use transit changes their behavior, and people are resistant to that. But if you encourage them to use electric cars, that works within their existing behavior. It’s an easier sell.

The overall trend of population density and household footprints offers another option, too. Pushing densities above 3,000 people per square mile can lower emissions substantially. That’s the tipping point in Jones and Kammen’s curve. Beyond that, they declined sharply, but then plateau. In other words, to make an significant impact, we just have to live a little closer together.

  1. The lowest emission rural areas are on par with people living in some major cities, though the densest cities still have the smallest footprints per capita.

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■ solar-roof

It’s no secret that living in the suburbs is a tad energy intensive. Low-density living practically requires owning and driving a car, which consumes a large portion of suburban households’ energy budgets. But there’s an upside to sprawl, too—plenty of space for solar panels.

Researchers in Auckland, New Zealand asked what the energy balance of the suburbs would look like if photovoltaic solar panels were widespread and how that would compare with denser urban centers. They looked at a range of dwelling densities, from a low of about 6 per acre in the outer burbs to a high of 52 per acre in the city. The researchers then imagined what would happen if solar panels were installed in every location that would be viable, typically on rooftops facing north and west (this is the southern hemisphere, after all).

In dense urban areas, the area available for solar panels was low on a per capital basis. In the suburbs, that flipped. The difference was so extreme that solar panels in dense parts of the city could only meet a fraction of the demand. But in the suburbs, there was actually an excess of electricity generated, so much so that households could own—and charge—electric cars and still not consume it all.

Now, there are some caveats to this study, namely that Auckland is a relatively sunny place despite its frequent seasonal rain showers. Solar radiation in the city is 1663 kW h/m2/y, which compares favorably with Barcelona in sunny and solar-friendly Spain, which averages 1613 kW h/m2/y. Not everywhere has the potential of those places. But those that do, particularly in the Southwestern United States, are also hotbeds of sprawl. Widespread adoption of solar power would certainly change energy budgets there.

Solar-powered suburbs wouldn’t be all green—there’s still the issue of habitat disruption and fragmentation. Yet those are concerns for solar power installations, too. There’s still strong demand for low-density living, so if we were to supplant large solar installations with solar panels with houses under them, that may not be such a bad trade-off.¹ Coupled with habitat-rich yards and parks, such developments could even be more ecologically productive than a solar plant (though still less than undeveloped land). That won’t stop some people from ragging on suburbs, but they’ll have a few less reasons to do so.

  1. I’d still like to see a direct comparison of how much less land is required for a solar installation compared with a solar-powered burb before making any final conclusions—this study didn’t go into that.

Image courtesy of John Callas


Byrd H., Ho A., Sharp B. & Kumar-Nair N. (2013). Measuring the solar potential of a city and its implications for energy policy, Energy Policy, 61 944-952. DOI:

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How far should you live from work?

Rush hour, New York City

Thirty minutes at most, according to the wisdom of the crowds.

That comes from reams of data and piles of research that suggests commute times tend to cluster around this point. People tend to be good at weighing their options, economists think. If you live farther from work, you can usually afford a bigger house or apartment. But there’s a point where that journey becomes too onerous, and you are willing to sacrifice some of those desires to live closer to your job. That point on average seems to be between 20 and 30 minutes.

I was inspired to look into this further after seeing an article by Charlie Gardner over at his blog, The Old Urbanist. Gardner had mined the American Community Survey for average commute times in major metropolitan areas. Though there was a tight correlation between population and commute time (metros with larger populations have longer average commutes), the differences weren’t pronounced. They ranged from a low of 22.5 minutes in Kansas City to a high of 34.6 in New York City. That’s not a lot.

But before we ask why commute times hover in a tight band, perhaps we need to ask why people commute so far in the first place. Why not work next door? The answers may seem obvious, but what’s readily apparent to one person may not be to another. That’s why we examine these things scientifically. Well, in this case your hunch is probably correct. An older study by Martin Wachs and his colleagues at UCLA found, unsurprisingly, that people choose where to live not just based on commute times but also neighborhood characteristics, schools, and safety.

Now we can move on to the more curious question, why commutes tend to average 20-30 minutes. It’s not just limited to the United States, either. In the Netherlands, the average commute time in the early 2000s was about 28 minutes. Many European nations average about 35 minutes. What makes a half-hour so universal in terms of commuting?

It didn’t used to be that way. Average commute times in 1980 were around 22 minutes. Today, they’re around 25 minutes. Three minutes may not seem like much, but remember it’s an average. To increase an average by that amount, some commutes had to grow significantly to counter those that shrunk or remained the same. Now, keep in mind there is a lot of variation about those averages. Some people travel 2 minutes to work, others well over an hour. But on average, they have increased.

What’s causing that lengthening is higher job densities in major metros. Job growth is requisite to economic growth, and vice versa. As metro areas add more jobs, those jobs tend to be concentrated in business districts (after all, not everyone can work out of their homes). And as business districts fill up, commute times lengthen because the roads leading there become more congested. So when the economy booms, traffic slows to a crawl. I heard anecdotal evidence of this when I lived in San Francisco. People told me, if you think traffic is bad now, it was much worse during the tech boom of the late 1990s. When all those tech workers lost their jobs, gridlock practically evaporated, they said.

Subtle changes in urban form may also cause longer commutes. One study in the Netherlands and another in Quebec, found that polycentric metro areas—those with two or more cities, like Minneapolis-St. Paul—tend to have longer auto commute times. As cities grow and begin bumping into one another, such agglomerations are likely to become more common. It’s possible commute times may increase as well. While there may not be consensus on this point, I haven’t found any studies that claim changes in urban form will shorten commute times. That makes sense if you look at somewhere like New York City, which is both monocentric and dense. People may work a short distance from their homes, but traffic is so congested and public transit makes so many stops that commute times are still relatively long. Simply increasing density in some cities may shorten commutes for a brief period, but the honeymoon won’t last forever.

Which is a bummer, because for the most part people think their commutes are too long. A survey of 2,000 commuters in the San Francisco Bay Area reported that 52 percent of respondents said they commuted at least 5 minutes longer than they would like. Among that group, median commute times were 40 minutes, which is certainly longer than the region’s average. On the other hand, 42 percent said their commutes were just right (their median time was 15 minutes). Surprisingly, 7 percent felt their commute was too short (median of 10 minutes). But despite the fact that a majority think their commute is too long, most people said they didn’t mind it, so long as their trips were less than 100 miles.

That people don’t mind their commute may be why commute times refuse to shrink. People in the Bay Area survey who didn’t mind their commute said they agreed with statements like, “I use my commute time productively” and “My commute trip is a useful transition between home and work”, which supports anecdotal evidence I’ve heard that people enjoy the separation between work and home. Twenty to thirty minutes may be just enough time to unwind.

It’s not entirely universal, though. Tolerable commute times seem to lengthen when people switch from cars to mass transit. People may find that time more productive, or maybe the time seems shorter because driving can be stressful, while just sitting usually isn’t. Personally, I know I’m willing to commute longer by train than car. Another reason is because mass transit commutes tend to be more reliable in terms of duration (at least for trains). Not having to worry about traffic jams doubling your commute is a big advantage.

Regardless of mode, people seem to settle on an ideal commute time. And once they have settled, they don’t seem to stray from it. A study of two metro areas in Washington State discovered that commute times don’t change much when people move or switch jobs. The thinking is that if a person gets a new job that’s farther away, they are more likely to move. Plus, as people have moved to suburbia, some jobs have followed. It’s a two-way street. But that doesn’t mean employers can move to the burbs without consequences. If an employer moves and an employee doesn’t move as well, the employee is more likely to find another job. Companies looking to relocate simply to cut costs may find the high turnover that results more costly in the long run.

Commuting is a big part of our lives, so it makes perfect sense that it would affect so much of the world around us, especially the cities we live in. Take a dense city like New York that has oodles of jobs, and lots of dense housing close in. That density helps keep commute times reasonable. But somewhere like Tulsa that doesn’t have as many jobs doesn’t have as much need for density. Form follows function, and currently the freeways in Tulsa are functioning pretty well compared with New York.

That presents a real dilemma for urban planners, who have been striving to increase densities in cities across the board. One approach has been mixed-use development that blends retail, housing, and office space. That may help reduce trip times for errands and such, but it doesn’t preclude people from living in one mixed-use neighborhood and working in another. The reality is, we’re probably not going to change commute times. If we offer faster and better transportation, people will use it until it becomes overburdened. At which point they’ll just move closer to work. Attempts to influence urban form through design may not have much of an impact if jobs don’t follow.


Cervero, R. (1996). Jobs-Housing Balance Revisited: Trends and Impacts in the San Francisco Bay Area, Journal of the American Planning Association, 62 (4) 511. DOI: 10.1080/01944369608975714

Cervero, R. & Duncan, M. (2006). ‘Which Reduces Vehicle Travel More: Jobs-Housing Balance or Retail-Housing Mixing?, Journal of the American Planning Association, 72 (4) 490. DOI: 10.1080/01944360608976767

Clark, W.A.V. & Davies Withers, S. (1999). Changing Jobs and Changing Houses: Mobility Outcomes of Employment Transitions, Journal of Regional Science, 39 (4) 673. DOI: 10.1111/0022-4146.00154

Clark, W.A.V., Huang, Y. & Withers, S. (2003). Does commuting distance matter?, Regional Science and Urban Economics, 33 (2) 221. DOI: 10.1016/S0166-0462(02)00012-1

Giuliano, G. & Small, K. (1993). Is the Journey to Work Explained by Urban Structure?, Urban Studies, 30 (9) 1500. DOI: 10.1080/00420989320081461

Levinson, D.M. (1997). Job and housing tenure and the journey to work, The Annals of Regional Science, 31 (4) 471. DOI: 10.1007/s001680050058

Schwanen, T., Dieleman, F.M. & Dijst, M. (2004). The Impact of Metropolitan Structure on Commute Behavior in the Netherlands: A Multilevel Approach, Growth and Change, 35 (3) 333. DOI: 10.1111/j.1468-2257.2004.00251.x

Schwanen, T. & Dijst, M. (2002). Travel-time ratios for visits to the workplace: the relationship between commuting time and work duration, Transportation Research Part A: Policy and Practice, 36 (7) 592. DOI: 10.1016/S0965-8564(01)00023-4

Vandersmissen, M.H., Villeneuve, P. & Thériault, M. (2003). Analyzing Changes in Urban Form and Commuting Time∗, The Professional Geographer, 55 (4) 463. DOI: 10.1111/0033-0124.5504004

Wachs, M., Taylor, B., Levine, N. & Ong, P. (1993). The Changing Commute: A Case-study of the Jobs–Housing Relationship over Time, Urban Studies, 30 (10) 1729. DOI: 10.1080/00420989320081681

Photo by Jekkone.

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Big parks or big lots?

Bubbler in a city park

The United States is not run by godless Communists. Neither is most of the rest of the world. In fact, the godless Communists that do remain are not all that Communist anymore. I bring that up because command and control economies can dictate what development happens where. Land conservation under such a system is technically easier, even if the actual results in Communist nations like the Soviet Union weren’t that inspiring. Land conservation in the free world is a trickier game, one played with carrots and sticks as opposed to edicts and directives. Here, money is your best friend.

Conservation organizations have focused on preserving big tracts of land, and rightfully so. Big buys are often more cost effective and easier to manage. But they’re also becoming trickier to execute in a world dominated by curving cul-du-sacs and one acre lots. If we want functioning ecosystems in these places, we need to focus on land conservation within the subdivision, not along its borders.

Luckily, the carrot seems to be working in those places. A study of subdivisions in Maryland between Washington, D.C., and Baltimore shows that developers have been incorporating more open space into their subdivisions. That’s not because they’re interested in land conservation. Part of it is a bit of command and control—Maryland’s Forest Conservation Act forces developers to conserve a modicum of forested land—but it’s also simple economics. Developers can sell lots and houses at higher prices if open space is nearby. Because proximity matters, that open space typically needs to be within the subdivision.

To developers, though, that open space is fungible. It can exist either as public parks or larger private lots—both raise prices. The Maryland study also found that minimum lot sizes—which governments typically use to preserve open space—can push developers away from shared open space toward larger lot sizes.

This poses a problem for maintaining healthy ecosystems. Like many laws, the way the Maryland Forest Conservation Act is interpreted matters. People can uphold the letter of the law—maintaining forest cover—without changing their usual habits—mowing their entire lot. The result is something that looks like a forest from above but doesn’t function like one.

In a perfect world, everyone would happily tend a few thousand square feet around their house and leave the rest to nature. But that’s not always the case. People will spend all Saturday mowing acres of grass and grumble about it afterwards. That’s because for many people owning a country manor is more alluring than owning a chunk of the great outdoors. You can fight that mentality by increasing minimum lot sizes to the point where mowing it all becomes completely unreasonable,¹ but the closer you get to a metro area, the less tenable that becomes.

There’s also no guarantee that laws dictating minimum lot sizes will remain in place. As the city creeps closer, pressure to further subdivide will mount. Open space preserved in private lots could easily disappear.

Parks, on the other hand, tend to stick around. Unlike large lots, they’re seldom subdivided. Instead, they tend to become institutions. People like their parks and are loathe to lose them—no one wants to see their neighborhood park disappear. So let’s put that to use. Instead of—or in addition to—minimum forest cover and minimum lot sizes, let’s institute minimum park sizes. Everyone will benefit. Developers will be able to sell lots at higher prices. Kids will have playgrounds. Adults will have walking paths. And because big parks often have big natural areas, ecosystems will have a better chance at surviving. It’s a solution that’s a bit more command and control than current vague regulations, but everyone will benefit. It’s also more carrot than stick. Even if you don’t particularly like carrots, it’s better than getting hit with a stick.

  1. Though there will always be exceptions—near where I grew up, one guy mowed 18 acres. He had to buy a bonafide farm tractor so it wouldn’t take him all week.

Photo by JD Hancock.


Lichtenberg, E., Tra, C., & Hardie, I. (2007). Land use regulation and the provision of open space in suburban residential subdivisions Journal of Environmental Economics and Management, 54 (2), 199-213 DOI: 10.1016/j.jeem.2007.02.001

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America’s suburban future

Aerial view of Carrollton, Texas

If you think American cities are sprawling now, just wait until 2025. In that time, the U.S. population will grow by 18 percent but the amount of developed land will increase 57 percent. Up to 9.2 percent of the lower 48 could be urbanized by then. And while that number includes cities and the infrastructure to support them—roads, rail, power lines, and so on—that number does not include land impacted by farming, logging, mining, or mineral extraction.

That 10 percent of the lower 48 could be crawling with people is a stark reminder that our nation—while immense—is not immune to the pressures of development. It’s also acknowledgement that despite years of hearing about the resurgence of American cities, sprawl is still king.

Today, it feels like much of what drove the suburbanization of America since World War II has changed. Incomes aren’t rising nearly as fast as they did in the 1950s and 1960s. In fact, when adjusted for inflation, incomes have stagnated or dropped in recent decades. Soaring gas prices and congested freeways have stolen some of the automobile’s glamor, too.

Yet two studies show that while the outlook in the U.S. may have changed, our desire for suburban living has not. The study’s results differ slightly—the 2004 paper says we’ll add 25.8 million hectares (64 million acres) by 2025, the 2009 manuscript says 22.4 million hectares (55 million acres) by 2030—but their conclusions are the same. American cities will continue to sprawl, adding more land per person than in the past.

In recent decades, the locus of suburbanization has shifted from the Northeast and Midwest to the South. With its warmer weather and lower costs of living, the South has grown faster than any other region in the U.S. since 1980. Development has been fueled by flat, cheap land and abundant freeways, which has pushed land demands well above the national average in some states.

That boom also meant the South was hit hard by the housing bust in 2008. But that doesn’t mean the market for suburban housing has disappeared. Living the burbs is still cheaper than the city, and since real incomes for most Americans have suffered in recent years, development will continue to chase lower land prices. The recession and housing slump may have put a damper on suburban development, but I’m guessing it’s just a temporary blip.

Another factor that should conspire against suburban development—higher gas prices—also doesn’t seem to have much of an influence. The 2009 study suggests development rates won’t take much of a hit from high fuel costs. To simulate rising gas prices, the study’s authors reduced the forecasted development rate in states where it was highest—primarily the car-centric South. Only 5 percent less land was converted from rural to urban uses.

It’s possible things could change—perhaps fuel costs will rise even higher, or maybe the home downsizing trend that’s in its infancy will mature. But I think we should prepare for a future filled with suburbs. In the South, where most of the development is happening, land continues to be cheap and easy to access. The same warm weather that drew many people there will also keep them in their cars. Nobody likes walking in the South’s sweltering summers, even if it’s just from the steamy parking lot to the over-air conditioned mall.

The question then is, how can we make the suburbs more environmentally friendly? Encouraging compactness would be a good start, even just at the subdivision level. Hopscotch development inflicts ecological damage well beyond its immediate footprint—there are many plants and animals that cannot survive surrounded by a sea of humanity. Dispersing job and commercial centers is another option, helping to reduce the number of miles people have to drive on a day-to-day basis.

In the end, though, we’ll have to push for more ecologically integrated development. We’ve seen small steps in that direction already—most new subdivisions must deal with run-off from rainstorms on-site rather than shunting it to an overburdened creek. It’s a start, but not enough to offset America’s suburban future.


Alig, R., Kline, J., & Lichtenstein, M. (2004). Urbanization on the US landscape: looking ahead in the 21st century Landscape and Urban Planning, 69 (2-3), 219-234 DOI: 10.1016/j.landurbplan.2003.07.004

White, E., Morzillo, A., & Alig, R. (2009). Past and projected rural land conversion in the US at state, regional, and national levels Landscape and Urban Planning, 89 (1-2), 37-48 DOI: 10.1016/j.landurbplan.2008.09.004

Photo by La Citta Vita.

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Farms giving way to subdivisions in Southeastern Wisconsin

If you were a squirrel living in Southeastern Wisconsin, you’d be pleasantly surprised by the state of things. In many places, there are as many—if not more—trees than there were 200 years ago. But that rosy image doesn’t tell the entire story. Comparing the forests that cover the cities and suburbs around Milwaukee—and likely in many places around the world—is like comparing Rome before and after the fall. It’s still Rome, but it’s not quite the same as it used to be.

Southern Wisconsin is a case study of the changes that were affecting much of the country in the 20th century. Most of the forests had been cleared in the 1800s by farmers, resulting in a landscape that little resembled what came before. The woodlots that remained were small and scattered. In one famous study, only 4.8 percent of the original forests remained by 1935. Milwaukee and its surrounding cities grew steadily in the run-up to World War II, but positively boomed thereafter. They needed room to grow, and since cleared land is easy to build on, farm after farm was subdivided.

The path from forest to front yard seems clear cut. A woods is cleared to make way for farmland, which is later subdivided into lots and sold off to make way for homes. But the reality is much more complex than that. Though a neighborhood may maintain its wooded appearance, it’s original character is gone.

In Wisconsin, subdivisions are invariably preceded by farms. Farming is a tough life. There’s not much money to be made with a small family farm, and an farmer’s property often doubles as his retirement fund. To maximize the investment, he’ll usually subdivide it for housing. It usually works out well for him, because land that’s good for growing crops is also good for building houses—it’s not too steep and most of it doesn’t need to be cleared.

That’s not to say farms are entirely devoid of trees. Most contain small woodlots and extensive fencerows that separated fields of corn, wheat, and soybeans. They’re relics of bygone forests, and in many places that’s all that’s left. Though the relationship is a bit one-sided, relic trees and farms have existed side-by-side for decades.

Maintaining that landscape during subdivision isn’t difficult. Building houses around trees is easy if you don’t take a cookie cutter approach, and houses with big trees in their yards tend to sell for more. But conservation rarely happens. That’s the conclusion of one study of Southeastern Wisconsin. It looked at the fate of extant vegetation as farms gave way to subdivisions between 1937 and 1975. Though the sum total of forested land didn’t drop as much as anticipated, very little of the original vegetation that made it through the transition. By 1975, the trees that dotted subdivisions and roadsides were almost entirely new.

That study reminds us that sum totals seldom tell an entire story. The relationship between forests, farms, and yards is complex and multidirectional. Forests are often cleared for farms, but abandoned farms can return to their forested state over time—much of New England underwent this process. However, urbanization can intervene along the way, removing the little remaining vegetation and replacing it with landscaped yards. But that’s not all the forest loss development is responsible for. Though many subdivisions are carved from land cleared previously for farms, they can be indirectly responsible for the loss of even more forests. Street and yard trees can’t offset this entirely. Similar patterns are well documented in developing nations. In Brazil, for example, expanding soy production has pushed cattle ranchers to clear land further into the frontier. It’s easy to forget these same processes are at work here in the United States.

Even when subdivisions spring fully formed from forested land—skipping the intermediate farm stage—their lots are often cleared of existing vegetation. Some of my research in graduate school documented the stark changes forest edges undergo when houses move in. In old black-and-white aerial photographs, the bare earth of cleared building sites stood out in stark contrast to the dark gray of the surrounding woodlands. Straight, sharp lines separated the two. In time, the edge bled back into the yards, but it wasn’t quite the same.

Suburban development isn’t going away anytime soon, but some of the structure and function of the old woodlands they replaced can be recovered. Homeowners can plant native trees. People can lobby their cities to plant native trees as well, rather than the whatever low-maintenance tree is in fashion among city foresters this year. The result won’t be the same as an intact woodland, but at least it will be similar.


Sharpe, D., Stearns, F., Leitner, L., & Dorney, J. (1986). Fate of natural vegetation during urban development of rural landscapes in Southeastern Wisconsin Urban Ecology, 9 (3-4), 267-287 DOI: 10.1016/0304-4009(86)90004-5

Photo by sierraromeo.

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Drive a lot? Housing density may not be to blame

Chicago streets at night

Pushing high density living may seem like a good way to get people out of their cars—saving them money, curbing emissions, and reducing oil dependence—but densification may not be a silver bullet, according to one recent study. The authors dug into the National Household Transportation Survey to examine per household vehicle ownership rates, vehicle miles traveled (VMT), and fuel consumption. While the results are by no means comprehensive or conclusive, they suggest that only the steepest increases in density could reduce car usage.

This post was chosen as an Editor's Selection for ResearchBlogging.orgDespite a correlation between density and car usage, other factors seem to play more important roles. Density is responsible for a fraction of annual VMT; increasing density by 1,000 housing units per square mile—a titanic leap, given that the average household is 2.6 people—reduces VMT by just 1,171 miles, all else being equal. Since that the average one-driver household in the study tacks on 10,100 miles per year, that represents just over an 11 percent drop in annual mileage.

housing density and Vehicle Miles Traveled

If you look at the numbers another way, the case for density reducing car usage looks even more tenuous. VMT only really declines substantially at the highest housing density—over 5,000 units per square mile, or about the same as Chicago. To halve VMT of the highest mileage households, you would need to increase housing density in those areas by 20- to 100- fold.

The inflexibility of our automobile usage boils down to a few factors, with work being the most important. The more workers in a household, the more drivers, and the more drivers, the more miles. A one-driver household, as noted above, tallies 10,100 miles per year; a two-driver household racks up 18,800 miles; three drivers, 33,900; four drivers, 47,700.¹ We are, by and large, beholden to our cars because we are beholden to our jobs. After that, driving increases as a result of income (richer people drive more), number of children (more and larger cars), education (higher education means more cars), and people’s life stage (households with older children have more cars).

While higher housing density doesn’t seem to reduce VMT, it does drive down fuel consumption. Households in the 50 to 250 houses per square mile range use 1,650 gallons of fuel annually, the most of any group. Every other group uses far less fuel. In the big cities, fuel usage drops to 690 gallons per household per year.² The reason? People with the space to use pickup trucks, SUVs, and vans tend to buy them more than people who live and drive on tighter city streets—they typically drive smaller, more fuel efficient vehicles. Yet this trend could be changing as we speak. Small car purchases have been increasing across the country, and anecdotally at least, I can confirm that large pickup trucks are harder than ever to sell these days.

fuel consumption and Vehicle Miles Traveled

One of the main arguments behind higher density living is that it will reduce our carbon footprint. While density may be a better long term solution, right now the most expeditious approach is to increase fuel economy. Rebuilding neighborhoods will take decades. In that time, most people will buy at least a handful of new cars, primarily for commuting to work. It would be great if everyone had access to mass transit, but for many, mass transit isn’t just a poor option, it isn’t an option at all. Those who do travel by bus or train today may only be a job change away from having to drive. Modern life demands mobility, and few things are better at providing that than the automobile.

  1. The increase from one to two drivers probably reflects some combining of trips by couples or roommates. The sharp increase from two to three drivers is probably the result of a family’s children driving to school or work.
  2. The lone outlier is areas below 50 houses per square mile, where households use 1,200 gallons per year. They probably have fewer nearby destinations, and so stay home more often.


Brownstone, D., & Golob, T. (2009). The impact of residential density on vehicle usage and energy consumption Journal of Urban Economics, 65 (1), 91-98 DOI: 10.1016/j.jue.2008.09.002

Photo by dsearls.

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Urbanites leave the car behind, but not as often as might think

Why the poor live in cities

Backyard neighbors and the perils of retrofitting suburbia

Accessory dwelling unit

Sprawl, in many cases, is in the past tense. It’s already happened. Though it continues in plenty of places, it’s most problematic where it already exists. For booming regions, sprawlish suburban rings threaten to choke the central city with snarled traffic and lean tax rolls. Rather than throw their hands up in disgust and move on to a city that “gets” it, a group of planners and architects have focused on retrofitting diffuse neighborhoods and intensifying four lane boulevards. In the process, there are myriad problems to tackle, but I’d like to tackle one right now: What to do with suburban housing.

Density is suburbia’s saving grace and Achille’s heal. Who wouldn’t want to be ensconced in their own private garden? But that same dispersed living isolates people and causes many of the headaches of daily life. Sprawl retrofit really means higher density living, which also means more shops close at hand and less time behind the wheel. It’s no secret that many suburban lots would easily support another house. Slapping another behind the existing one is a simple way to double the density. It’s a common approach to sprawl retrofit, and one raised at the 19th Congress for the New Urbanism. But if erecting backyard residences solves one set of headaches, it risks inflicting more in the process.

Suburban homes were built with very specific ideals in mind. The front of the house is the public side, presenting its widest part to the street, shielding the backyard and creating a private area where people can relax in relative peace. While many early car-centric suburban houses reacted tepidly to the backyard—the best they offered were a few more windows and a back door—we soon became practiced in the art of suburbia. Large picture windows, sliding doors, four-season rooms, and covered porches quickly festooned the private side. The backyard became more than an outdoor amenity—it was a private garden to be enjoyed from the indoors, too.

Hacking a lot in two and adding a second residence could destroy one of the few things many suburban homes have going for them—a sense of privacy. The attractiveness of this feature should not be underestimated. Research suggests that open views are help ensure a feeling of privacy, even more so than actual proximity. The bad of suburbia—houses turning their backs on the street—was driven by a noble aspiration—homes embracing the yard. No one wants their view to embrace another home, no matter how beautifully designed.

And so a lynchpin of sprawl retrofit—boosting the number of houses—may be the most difficult to achieve. That’s not to say it cannot be done, but it will require careful consideration to do properly. Suburbia may be, in many ways, a consequence of bad planning, but it got one thing right—the yard. We crave green, open space, and suburban lots with suburban houses have it in spades. It may have given us too much, but we shouldn’t take it away in too much haste lest we compound the mistakes of the past.

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It’s not the yard that matters, it’s the view

Photo by faceless b.

Why the poor live in cities

Cabrini-Green, Chicago

If you ask any big city mayor what is one of the most pressing problems facing his or her city, I’m guessing poverty will be high on the list. Cities across the United States are filled with pockets of hardship, and while rural poverty is widespread, too, impoverishment within metropolitan areas tends to be strikingly concentrated near downtown. Did the rich flee or the poor converge? One study says transit provides the answer.

The article begins with pages of hypotheses, formulae, and tables, but the real history of the trend is buried at the end, just before the conclusion. The key to it all is the fact that public transportation is a distinctly modern invention, and before its advent, most people lived within walking distance of their jobs, regardless of income.

It is in the late 18th and early 19th centuries that we get a geographic glimpse, uninfluenced by modern public transit, at where the rich and poor lived. Proximity to employment dictated where people lived, and people, then as now, worked everywhere. Even the most successful hedge fund’s offices are cleaned by janitors who make little more than minimum wage, and this maxim held true back in the 18th and 19th centuries as well. The difference then was that the middle-class, the well-to-do, and even some of the wealthy walked to work. Only the fabulously wealthy had hansom cabs and carriages to take them about.

When mass transit started catching on, it was mostly enjoyed by those with money, like most new technologies. Affluent types began fleeing the city for “streetcar suburbs.” But as transit prices started dropping, a new technology burst onto the scene—the automobile. For the rich, cars were far better than cramped street cars. They could travel from home to work in relative privacy (though comfort was not a given due to the poor condition of most roads in those days). Plus, cars doubled as a status symbol.

Again, the poor were stuck in the city, and many remain stuck there today. The cost of owning and operating a car is simply beyond reach for a chunk of society. And given the limited reach or slow speed of many American mass transit systems, people without cars need to live closer to their jobs, which are typically in the city.

It’s a tidy narrative, and one that the study backs up with both anecdotal snapshots,¹ statistical models, and data-driven time points from the modern day. The modern observations paint a convincing picture, and one that backs up the narrative. In cities with extensive subway systems, the study found that incomes dip slightly within a one-mile ring of downtown—where land values drop but remain accessible by transit—and then rise and hold steady from three to seven miles out. Transit usage also rises after that first mile, peaking two miles out, where incomes begin to rise. This peak exists in those cities because rail systems—they move far more quickly—appeal to more than just the poor. Wealthier people are more willing to forsake their car for a train and a simpler commute. But in newer American cities without subway systems, buses rule. In those places, most people with sufficient means pay for the shorter commute by car.² The final piece of evidence lies in the geographic distribution of jobs. In “old” American cities with extensive transit, 55 percent of the jobs in the metro area are within five miles of downtown. In “new” cities, 81 percent of jobs are more than five miles out.

The evidence in this paper led me to a few conclusions of my own. First, since the poor are less likely to use roads and highways, government highway subsidies are regressive, that economic term that describes a policy that benefits the rich more than the poor. That makes transit subsidies progressive, but even that is an oversimplification. Transit gives the poor greater access to employment, which will hopefully make them not poor in the future. It also boosts property values in the near vicinity. Since the better-off can afford pricier houses, they clearly benefit, too. Still, some communities fail to understand transit’s merits, instead equating it with an influx of poverty. These rich communities³ will eventually need more viable transit options, though, because they employ poorer people to do the things they’d prefer not to do. And as gas prices rise, no one will want to pay through the nose for that privilege.

  1. “…in New York, 52 percent of workers earning less than $10 per week walked to work in 1907. Only 12 percent of workers earning $20 per day used that form of transportation, and instead used streetcars. Just as the car today favored the non-poor, the streetcar did in the past, and it helps to explain why the poor lived close to the city center 100 years ago.”
  2. This in turn gives the non-poor in those cities a negative opinion of transit. As in, “Only the poor take the bus.”
  3. Parts of Orange County, I’m looking at you.


Glaeser, E., Kahn, M., & Rappaport, J. (2008). Why do the poor live in cities The role of public transportation Journal of Urban Economics, 63 (1), 1-24 DOI: 10.1016/j.jue.2006.12.004

Photo by reallyboring.

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Tell me how much you drive, and I’ll tell you where you live

I-80 and M2

Travel can be revealing. In many cases, “where” can answer as much about a person as “who.” Much of who we are is tied up in what sorts of stores we frequent, where we work, and where we go for fun. While that sounds creepy—especially given the recent furor over smartphones storing location information—city-wide travel trends can help explain a lot about where we live.

A study comparing British and American travel habits discovered that trip distances in the United States predictably lengthen as the population thins out. In Great Britain, though, that relationship isn’t as strong, in part due to its greater population density. But when the researchers filtered out differences in income and density between Great Britain and the U.S., the British still traveled less.

The reason behind the travel discrepancy, the researchers suspect, lies in the strict separation of space for living, working, and shopping that is common in the U.S. To arrive at that conclusion, they had to use a bit of mathematical cleverness to make an apples-to-apples comparison. The model compared British and American cities of similar population and density, but shuffled the contents of the American ones until their general urban form resembled their ale-swilling counterparts. This meant that shops were now next to houses, grocery stores located just down the street, and pubs scattered about town. The results suggest that the jumbled urban land uses in England, Scotland, and Wales keep the lid on travel distances.

The British also get out from behind the wheel more often, using their feet for something other than operating gas and brake pedals. Whereas under 7 percent of trips in the U.S. are taken on foot, nearly one-third are in Great Britain. And while almost 90 percent of trips in the U.S. are made by car; only 58 percent are in Britain. More people in Britain take buses and trains, too. This modal flexibility could help explain why British of different incomes tend to take similar numbers of trips, unlike in the U.S. where wealthier people step out more often. In both countries, though, wealth is still tightly correlated with mobility, which is partially reflective of people’s ability to own, maintain, and fuel automobiles for such trips.

The one odd bit the researchers discovered was that people in smaller metropolitan areas—with populations between 250,000 to 500,000—traveled more frequently than larger ones. In theory, residents of large metro areas should have more available destinations and ways to get there, which left them stumped as to why big city people made fewer trips. My suspicion? Smaller metro areas may be a sweet spot in the spectrum, with just enough destinations and modes of transportation without the congestion present in big cities.


Giuliano, G., & Narayan, D. (2003). Another look at travel patterns and urban form: The US and Great Britain Urban Studies, 40 (11), 2295-2312 DOI: 10.1080/0042098032000123303

Photos by Minesweeper and Loganberry.

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Urbanites leave the car behind, but not as often as you might think

The great (big) American lawn

A lawn being mowed

Spring is descending on the United States. Buds on trees and shrubs are swelling, and brittle brown grass is beginning to show green signs of life. As people put away their snow shovels and dust off their lawn mowers, it’s also a good time to take stock of the American lawn, which plays a starring role in the American dream. Backyard barbecues or weekend touch football games wouldn’t be the same without them, and there is something pleasing about a house perched amidst a nice green carpet. But grass is also a fussy plant, needing to be watered, fertilized, weeded, and, of course, mowed. For many, lawns are an American nightmare, yet we love them anyway.

Some Americans like to say they bleed red, white, and blue, but many should probably add green to that list, such is their devotion to their lawns. I myself am intimately acquainted with lawns and have been for many years. I started mowing my parents’ lawn as soon as I could safely see over the mower’s handle and took on a handful of my neighbors’ shortly thereafter. It didn’t take long until I was a lawn mowing connoisseur, changing the cutting pattern with every mow to give the yard a bit of golf course confidence. Even in college I couldn’t escape lawns. One of my summer jobs involved navigating a Toro Groundsmaster 322-D across school yards for eight hours a day. Even today, I still like the smell of freshly cut grass.

Our attachment to lawns means they have moved with us, even to climates where no lawn has any right to grow. Given how large they figure in the American subconscious, just how big is the collective American lawn? Nearly 50,000 square miles. That’s three times more than the area of irrigated corn in the U.S. And we grow a lot of corn. We’re still rolling out the green carpet, too. Between 1978 and 2001, we added between 170 and 355 square miles of lawn each year (depending on how you estimate it).

Much of that growth has come from the expanding suburbs. Lawns aren’t necessarily bigger than they used to be—in fact, median lot sizes have decreased while houses have continued to grow.¹ Part of the reason is that two story houses are more popular than before. Whereas only 23 percent of homes built in 1973 were had two stories, 53 percent do today.² So while houses have increased in size, lawns have kept pace, if only because they’ve reclaimed some of the built footprint.

More land under the seed-water-fertilize-mow regimen means more chemical applications, too. And given the intensity with which we dose our lawns, that should concern us. About 71 million pounds of active ingredients of herbicides, insecticides, fungicides, and other chemicals are dumped on U.S. lawns each year, or about 7 percent of all pesticides used in the U.S. Lawns may be attractive greenery, but they’re anything but green.

That’s not to say we should do away with lawns entirely. No way. But perhaps we could all do a little better by following two maxims my dad has for his lawn. First, he reasons that more fertilizer means more mowing. He applies it like a diabetic sugars his coffee—sparingly. It’s just enough to prevent our yard from becoming a neighborhood disgrace, but it’s a savvy approach. Some of our old neighbors fertilized religiously and therefore mowed religiously. The second mantra speaks to lawn size. “If the lawn takes longer than half an hour to mow, then it’s too big,” he says. While the half-hour rule was never entirely accurate—I paid close attention to how long I spent behind the mower—it’s the idea that matters. Our back yard was wreathed in butternut trees, general shrubbery, a small pond, and an honest-to-goodness prairie, all there, in part, to cut down on the amount of grass we had to maintain.  Some people might balk at giving up that much turf, but I can assure you, it was still enough for a weekend game of football with my friends.

  1. Average lot size—which is skewed by mammoth properties—has grown slightly since 1976.
  2. Fun fact: Split level homes which were all the rage in the 1970s and 1980s peaked at 12 percent of new homes in 1975 and 1976. Today, their numbers are little more than a statistical hiccup.


Fishel, Frederick M. 2011. Pesticide Use Trends in the U. S. : Pesticides for Home and Garden Uses. PI-140. University of Florida Institute of Food and Agricultural Sciences Extension.

Grube, Arthur, David Donaldson, Timothy Kiely, and La Wu. 2011. Pesticides Industry Sales and Usage: 2006 and 2007 Market Estimates. U.S. Environmental Protection Agency.

Lindsey, Rebecca. 2005. Looking for lawns. NASA Earth Observatory.

Robbins, P. (2003). Turfgrass revolution: measuring the expansion of the American lawn Land Use Policy, 20 (2), 181-194 DOI: 10.1016/S0264-8377(03)00006-1

U.S. Census Bureau. 2010. Characteristics of New Housing.

Photo by seantoyer.

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It’s not the yard that matters, it’s the view

Plants rockin’ the suburbs, animals not so much

Keep your eyes to yourself

Crowded sidewalk in New York City

There’s an unwritten rule followed by nearly all city dwellers—never make eye contact. If you attempt to do so, your glance will be met with utter disregard. You do not exist, other than being an object to avoid. I learned this the hard way. Upon moving to San Francisco from Minnesota—the friendliest of all possible places—I would attempt to make eye contact with strangers on the street out of courtesy. In Minnesota, this is commonplace. There, my glances were often met with a polite smile or a courteous “hello.” In San Francisco—even on streets that were anything but crowded—they were ignored with complete indifference.

Imagine, then, my surprise when I learned of San Francisco’s reputation as a friendly city. If San Francisco is considered friendly, I thought, then I’m steering clear of New York. I mused that such indifference to others must be an artifact of city life. That’s not to say there aren’t friendly people there—it’s true that San Franciscans are a generally genial bunch once you get them off the sidewalk, as are the New Yorkers I’ve met and nearly every other person from a big city. But when I’m in a small town, things sure do feel different. Walking down the street is no longer a sterile affair. It’s no family reunion, but it is degrees warmer than in cities. Still, my own experiences weren’t enough to convince me that this could be a universal trend.

Luckily, my hunch was proved correct the other day by a study which compared the rates of eye contact among people in central Philadelphia, suburban Bryn Mawr, and rural Parkesburg. The study’s authors parked two college students—a guy and a girl—outside a post office and a store in each location for two hours. The students counted the number of people who made eye contact and if anyone said “hello,” “how are you,” or the like. Lo and behold, rural Parkesburg held true to the small town stereotype. Between 70 and 80 percent of passersby glanced at the stationary students in the Parkesburg, while just 10 to 20 percent did in Philadelphia. Bryn Mawr’s pedestrians fell predictably in the middle, with around 40 to 50 percent making eye contact.

The rural types were also much more likely to say something to the strangers. One quarter of people in Parkesburg opened their mouths in greeting, while just three percent did for Bryn Mawr and Philadelphia combined. (The city center was by far the least friendly—only one person said something to each person at both the post office and the store.) In addition, everyone who did say something did make eye contact.

The study’s authors contemplated a few possible explanations for why the city dwellers were so hesitant to make eye contact. They favored the sensory overload hypothesis—that people in big cities are surrounded by too many people, noises, and other distractions—though they also speculated that city folk may fear strangers more or that small town people may be more curious about strangers. They also touched on the idea that city people are more hurried than either suburban or small town people. This notion has been covered both before and since by a number of different researchers. In general, people in larger cities do tend to walk faster, so there may be some truth to this.

Whatever the reason, I admit I exhaled a slight sigh of relief when I discovered that science confirmed my suspicions. San Franciscans, New Yorkers, Londoners—no matter how friendly they are underneath, suffer the same aversion to eye contact as other big cities. Small towns do feel friendlier.


Newman, J., & McCauley, C. (1977). Eye Contact with Strangers in City, Suburb, and Small Town Environment and Behavior, 9 (4), 547-558 DOI: 10.1177/001391657794006

Bornstein, M., & Bornstein, H. (1976). The pace of life Nature, 259 (5544), 557-559 DOI: 10.1038/259557a0

Bornstein, M. (1979). The Pace of Life: Revisited International Journal of Psychology, 14 (1), 83-90 DOI: 10.1080/00207597908246715

Wirtz, P., & Ries, G. (1992). The Pace of Life – Reanalysed: Why Does Walking Speed of Pedestrians Correlate With City Size? Behaviour, 123 (1), 77-83 DOI: 10.1163/156853992X00129

Photo by Susan NYC.

Hidden cost of sprawl: Getting to school

The cost of getting to school

click for more detail

Chalk it up to the law of unintended consequences. As Americans have flocked to the suburbs for the lower cost of living, the cost of sending their kids to school has gone up. Where most kids used to walk to school—myself included—nowadays many simply live too far away. While some students get rides from their parents, many are left to take the bus, an option that is funded by districts. But as kids travel farther to get to school, the costs for busing them have also gone up.

Fully 56 percent of people living in metropolitan areas in 1950 resided in their region’s big city (or cities). By 2000, that proportion had dropped to 32 percent. At the same time, the cost of sending kids to school has increased from $289 per student to $737 per student.¹ It might be tempting to blame gas and diesel prices, but they aren’t responsible—they’ve remained largely constant over that time period when adjusted for inflation (except for the energy crisis in the 1970s). Yet the trend in student transportation costs has risen unabated. Though the outlay may not seem significant, it is money that would be spent more effectively in the classroom.

  1. All costs are inflation adjusted to 2007 dollars.


Boustan, Leah Platt, and Allison Shertzer. 2010. Demography and Population Loss from Central Cities, 1950-2000. California Center for Population Research Working Paper PWP-CCPR-2010-19. Available online.

U.S. Department of Education. 2009. Digest of Education Statistics. Table 147.

The roadless neighborhoods of Radburn, New Jersey

Walkway in Radburn, New Jersey

Planners looking to imbue their development with a little old school appeal have a best friend in alleys. The petite thoroughfares tuck bland garage doors behind friendlier looking houses, shrink lots to squeeze in more housing, and leave sidewalks and streets that are free of driveways and curb cuts. Alleys have their charm, I admit. They harken back to the day when they hosted neighborhood stickball games or were the best place to ride a bike. New Urbanists—planners, architects, and developers who seek to recreate Small Town, U.S.A.—have latched on to alleys. They claim that the narrow passages leave a streetscape that’s friendlier to pedestrians. It’s a good argument, but I think New Urbanists just have a bad case of nostalgia.

Here’s why: If pedestrian friendliness and walkable neighborhoods are really what New Urbanist planners seek, then they would do away with the alley entirely. Well, not entirely. Rather, they would pick up a neighborhood’s roads and plop them down in place of the alleys. In the street’s place would be narrower pedestrian and bike paths. The roadway would remain behind the houses, functioning as an alley in spirit while feeding roads that carry traffic to larger arterials. People and cars could both travel in relative peace.

The separation of foot and vehicle traffic sounds like a brilliant idea, one that could bequeath neighborhoods with New Urbanist density and pedestrian friendliness while preserving a bit more space for yards and gardens. In fact, I think it’s so brilliant that I wish I could claim it as my own. Alas, I cannot. Credit goes to Clarence Stein, Henry Wright, and Marjorie Sewell Cautley, the planners of Radburn, New Jersey.

Radburn cluster planRadburn was cooked up in the 1920s. At the time, the success of the automobile encouraged experimentation with city plans. The Radburn plan was at the cutting edge. Cars brought a new freedom of movement that many planners translated into larger lots and sweeping lanes that evoked the countryside, à la Frank Lloyd Wright’s proposed Broadacre City. But Stein, Wright, and Cautley took things in a slightly different direction, shrinking roads and lots back to more manageable sizes.

I first read about Stein, Wright, and Cautley’s plans for Radburn in The American City: What Works, What Doesn’t. It was the plan’s walkways that captured my imagination. They weren’t just footpaths—they were spiritual successor to the road. Front doors opened on to the paths. Pedestrians never had to worry about vehicular traffic. Instead, the footways passed under streets, keeping dangerous automobiles separate from pedestrians—especially children walking to school.¹ Since I read about Radburn, I’ve been so taken by the idea of “roadless” neighborhoods that they’ve backdropped my dreams. I kid you not. I often walk through Radburnesque towns in my sleep-induced hallucinations.

Alas, Radburn was never finished. Its pioneering planners and their model city ran smack into the financial realities of the Great Depression. Only one of the pedestrian underpasses—what was to be one of Radburn’s signature elements—was built. Instead, Radburn is best known for introducing the 20th century to the cul-de-sac and the superblock, a collection of streets bounded by four major arterial roads. Alexander Garvin, author of The American City, says these two planning concepts were “so much more important” than the footpaths and their underpasses. He was certainly right about their role in the last century, but I’d like to think the next hundred years will prove him wrong.

  1. An interesting side note: Radburn’s planners defined each neighborhoods by the “population for which one elementary school is ordinarily required”.


Alexander Garvin (2002). Residential Suburbs The American City: What Works, What Doesn’t, 305-343 ISBN: 0071373675

Photo by themikebot.

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It’s not the yard that matters, it’s the view

When greenbelts fail

Leapfrog suburb in the Easy Bay, California

Parks are often preservationists’ first line of defense against sprawl. To many, they’re a win-win arrangement—less rambling development and more open space. But the same qualities that make them attractive to planners—higher property values, more recreational opportunities, and pleasing aesthetics—also draws new residents, undermining their sprawl-fighting virtues.

Greater London and the San Francisco Bay Area are good examples of the failure of greenbelts to stem outward expansion and encourage upward growth. Regional parks surrounding the core metropolitan area have become assets for communities outside the belt, attracting residents. So long as people have an expedient way to get to work, they’ll happily sacrifice proximity to work for a little patch of sunshine and greenery they can easily visit.

That’s the mechanism behind suburbs that leapfrog parks and greenbelts, according to two resource economists. They created sophisticated models that produced simplified SimCity maps that allowed them to see how parks of different sizes and shapes could change development patterns. Without parks, cities appeared as perfect circles on the map, with the highest density areas in the middle. The addition of a park, however, drew people away from downtown, creating a second locus of high-density development around it much the same way Central Park has attracted Manhattanites. But they found that if New York had an attractive space like Central Park outside of city limits, its population would be smeared across the landscape like butter on bread rather than centered on Manhattan like a dollop of ice cream. Typical parks with low perimeter-to-area ratios tend to affect development this way.

Greenbelts on the other hand have gobs of perimeter, making them easy to access for large numbers of people. The perimeter-to-area difference between classic parks and greenbelts means they have  different effects on development, at least within the confines of the paper’s model. Where classic parks spread development by acting as a second downtown, greenbelts that bound a city can hem it in. By diffusing a park’s benefits around the city rather than concentrating it in one place, greenbelts’ recreational values are typically lower than a classic park but accessible to more people. People want to live close to both open space and their jobs, so a properly configured greenbelt can boost neighborhood density between itself and downtown, limiting sprawl.

For greenbelts to be truly effective, the paper’s authors note, they must be sufficiently wide to discourage casual commuters from living outside its bounds. This is likely why greenbelts around cities like London and San Francisco have failed—they just weren’t big enough. Furthermore, while greenbelts can keep development inwardly focused, new parks within city limits can spur redevelopment of underpopulated areas. Together, they could be a powerful double whammy against sprawl.

Whatever the case, it’s clear that cities’ open-space strategies need to be well though out. Poorly planned park systems can have consequences that are not just unintended, but counterproductive.


Wu, J. (2003). The influence of public open space on urban spatial structure Journal of Environmental Economics and Management, 46 (2), 288-309 DOI: 10.1016/S0095-0696(03)00023-8

Photo by Troy Holden.

It’s not the yard that matters, it’s the view

Small yards

Americans love their privacy. Most aren’t keen on high rises or even attached condos, having been imprinted with a very specific American dream—that of a single-family house on a quarter acre lot. I’m one of them. But as populations in cities and suburbs boom, there’s simply less land to go around. The result of cramming detached homes into smaller spaces is often comical. With McMansions and McMansion, Jrs. shoulder-to-shoulder, the lots they sit on look like last year’s outfit on a six-foot sophomore.

Yet despite the potential aesthetic faux pas, many people want a single-family house. A lone house—never mind the neighbors six feet to the left and right—engenders feelings of independence and privacy. It’s self-sufficiency framed in two-by-fours. This is what planners and developers are up against as they struggle to fit more homes onto less land.

Such tight spacing of big houses has always been a bit of a mystery to me. The yards behind sardine houses are clearly more decorative than functional, so what’s the point of them? Wouldn’t everyone be happier if they lumped their token yards together? The resultant space would be magnitudes larger and more usable. But privacy would suffer. Or would it?

Maybe not. Homeowners feel just as happy and secluded in a single-family house as in a townhouse, so long as they have good views out their windows, according to one survey. The study asked homeowners in two neighboring developments—one with single-family houses and the other with townhouses—how they felt about their homes, their privacy, and their access to open space. Most people were happy, but the most satisfied were those whose views didn’t look directly onto the neighbors.

The differences between townhouse owners with views and without views were the most revealing. People with an open view were more likely to say they had enough space and privacy. Naturally, those with good views were also pleased with the way the subdivision was laid out, a trend which was echoed by owners of the detached single-family houses. The happiest people were those with homes that opened out onto undeveloped land like a flood plain or communal open space.

Given American’s penchant for privacy, I was surprised that owners of townhouses were more satisfied than owners of detached homes. The townhouses’ compact footprints may have given them an advantage. With 12.5 units per acre, the townhouse development was 2.5 times denser than the site with single-family houses. With the remaining space, the developers set aside 3.25 acres of open space. Though their motives for doing so weren’t clear—ordinances may have demanded it—it certainly had a positive effect on the way people viewed their own homes.

The market wasn’t as kind to the townhouses, however. Owners reported difficulty selling them while single-family houses in the neighboring development were selling like hotcakes. (This was during the mid-1990s.) So although people appear to be happy with attached housing once they’ve experienced it, most people crave the perceived privacy of single-family houses. Still if you’re looking for a home, it’s important to keep in mind that a grassy buffer may not be the path to happiness. What we see out our windows may have a larger effect on our sense of space and our happiness.


Day, L. (2000). Choosing a House: The Relationship between Dwelling Type, Perception of Privacy and Residential Satisfaction Journal of Planning Education and Research, 19 (3), 265-275 DOI: 10.1177/0739456X0001900305

Photo by IDuke.

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Plants rockin’ the suburbs, animals not so much

tufted hair grass (Deschampsia caespitosa) in a yard

Where there are more people, there’s less nature. It’s a fairly well established fact. Manhattan may have the odd hawk or falcon, but the paved island’s diversity of plants and animals just can’t compare to that of 23 square miles of pristine wilderness. What’s less known is how well biodiversity fares in human landscapes that are somewhere between the Empire State Building and Daniel Boone’s back forty.

Many scientific papers have been written about how specific types of plants and animals fare in the countryside, the city, and places in between, but few summarize the big picture. One review paper did take a wider view and surveyed 105 studies. It found that though most types of animals avoid the city, plant life seems perfectly happy living the suburban dream.

Animals, specifically mammals, reptiles, and amphibians,¹ dropped precipitously in most studies as researchers moved from the countryside to the city. In the first transition—from the countryside to the suburbs—only three studies found the same or greater numbers of mammal, reptile, and amphibian species, while 14 studies reported fewer. Invertebrate diversity rose in 14 studies, but fell in 30 others and remained the same in only three reports. These negative trends were magnified in the transition between the suburbs and the city proper. All but one study reported the same or fewer numbers of species of invertebrates in the big city as in the suburbs. As the researchers moved into the city and human population density increased, they found fewer mammal, reptile, and amphibian species.

Loss of habitat is probably behind this steady decline. Larger animals like mammals, reptiles, and amphibians need relatively large plots of land to survive. Invertebrates like insects are better off in human-dominated areas because of their smaller size—even a single tree can support dozens of different insects.

Amidst the gloom, plants were the one bright spot. In the suburb-city transition, plant diversity advanced in seven studies and retreated in seven others. It thrived when moving from the countryside to the suburbs. Plants’ success is probably due to their negligible requirements. Many only require a bit of soil, some water, and moderately clean air. On top of that, people often lend plants a helping hand by planting, watering, and fertilizing them. And while a home may have a cat and a dog, many sport dozens of different flowers, trees, and shrubs in their garden. Suburban lots are both large enough to encourage gardens yet small enough for people to support more diversity than on sprawling country lots. Even different landscaping preferences between different households fosters higher diversity.

Suburban plant diversity, though, probably comes at the expense of native flora. Most yards are beautified with species exotic to the area. Many are chosen simply based on their appearance or low maintenance. Native gardens are becoming more popular, but their numbers still pale in comparison to more traditional yards. It’s my suspicion that non-native landscaping holds down the diversity of mammals, reptiles, amphibians, and invertebrates. Native plantings would probably aid native animals, helping to offset some of the land taken by development.

  1. This review did not include birds—there are so many studies of birds in cities that it would be another paper in and of itself.

McKinney, M. (2008). Effects of urbanization on species richness: A review of plants and animals Urban Ecosystems, 11 (2), 161-176 DOI: 10.1007/s11252-007-0045-4

Photo by pluckytree.

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Do people follow trains, or do trains follow people? London’s Underground solves a riddle

Notting Hill Station, London Underground

Transit oriented development is all the rage in urban planning these days. Proponents claim new transit coupled with mixed-use zoning will ignite growth in otherwise struggling areas. Detractors claim running new lines to low-density neighborhoods will leave cities burdened with white elephants. Overall, reality is probably somewhere in between, but transit and population density is a real chicken-or-the-egg problem. Which comes first?

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Greater London is perhaps the perfect region to explore this question. Home to the world’s first metro system, London was also one of the first cities to explore transit oriented development. The Metropolitan Railway (the Underground’s former name) had the authority to coordinate rail lines with housing development, which it leveraged to the tune of 15,000 houses on 2,200 acres. It also built lines to serve neighborhoods already teeming with people.

But the Metropolitan Railway did not have a monopoly on rail transport between London and the suburbs. Other companies both served existing towns and built new lines to otherwise underpopulated regions. Some teamed up with developers in the hopes of ensuring a steady stream of riders. Others lines were purely speculative, with owners hoping that development would follow.

Fortunately for the Metropolitan Railway and other companies, the majority of speculative rail lines were successful in spurring growth, according to a 2007 research paper. The study examined two hypotheses: One, that transit oriented development works, and two, that transit follows population density. Both proved to be true. The paper’s author found that population density was driven by the presence of train stations, and that the presence of train stations could be explained by population density. For each one percent increase in rail capacity, population density increased nearly a quarter of a percent. And each one percent increase in population density over ten years leads to about a one quarter percent increase in train station density. “Train service led to a suburbanization of countryside and increased population of new developments, which attracted more railways,” he wrote.

Mass transit, at least in the case of rail, appears to both drive development and benefit from it. Furthermore, the study claims, the Underground has helped build London’s city center into the commercial powerhouse it is today by fostering commuting from the city’s periphery. With more people commuting from the suburbs, commercial space could expand within the city center. And as people moved out of the city center, the sorts of traffic the Underground carried began to change too, adding more business-to-business traffic than before. The shifting uses of the London Underground can also inform future transit planning. Building systems to merely serve existing commuting traffic will likely result in an overburdened system.


Levinson, D. (2007). Density and dispersion: the co-development of land use and rail in London Journal of Economic Geography, 8 (1), 55-77 DOI: 10.1093/jeg/lbm038

Photo by drewleavy.

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Suburbia no more? Not quite yet

Aerial view of a new subdivision

Travel just outside any large American city and one of the things you may notice is the number of new construction projects. Fresh, undeveloped land on the fringe of a metropolitan area is land ripe for the picking, every developers dream. The pace of suburban development, it would seem, has not slackened since it started in the 1950s. But things are not always what they seem. Though many major American cities are continuing to grow, each person they add is taking up less land than the person before them. From Houston to New York to Los Angeles, cities are consuming land at a slower rate than before.

The study that stumbled upon this nugget was originally looking for links between types of zoning laws and the amount of land consumed per additional person in a metropolitan area. They found that cities with ordinances that encouraged the redevelopment of old sites within city limits reduced their per capita land consumption by twice as much as cities with more traditional zoning laws. Overall, major metro areas in the U.S. added 1,184 square feet (110 square m) less land per person in 2000 than they had in 1990. Additionally, in cities that did slow their rate of per capita land consumption, more people settled in denser neighborhoods. The study shows that zoning laws do have an effect…sort of. It turns out that zoning laws are not entirely responsible for the change.

Part of the proof is the fact that four of the major Texas metropolitan areas grew and consumed less land per capita, too. If you’ve ever visited or flown over any of these cities—Houston, Dallas/Ft. Worth, Austin, San Antonio—you know they don’t keep a tight leash on development. I’ve visited or driven through each of them over the years, and I got the impression they were sitting atop massive suburban volcanoes, spewing strip mall magma and tract housing pyroclastics. Since Texas does not have many natural barriers to impede city growth, you’d think its cities would just keep growing. Except they haven’t.

The study’s authors don’t touch on possible reasons behind the Texas anomaly—there were too few metro areas that followed the zoning creed to make any statistical inferences—but I have hunch why their rate of per capita land consumption is dropping like a stone. Without trains to rapidly move people from place to place, the freeways and tollways have become saturated with traffic. Large, low-density cities simply take too long to traverse. People in Texas may be warming up to higher density living, but not after thousands of square miles have been gobbled up by Walmarts and Whataburgers.

The sprawling cities of the Southeast may want to take notice of what’s happening in Texas. Though many saw their per capita land consumption slow as well, their urban cores did not grow any denser, suggesting they may follow a very Texas-like trajectory. On the other side of the country, many Western cities, such as Phoenix, have already reached their saturation points and have begun to densify.

Still, not every city is building up instead of out. The Grand Forks, ND, metro area, for example, has been adding a whopping 1.3 acres (0.54 ha) per person, compared to the New York metro area, which has added only one tenth of an acre (0.05 ha) per person.

While inward-looking zoning laws have reduced the rate at which cities are expanding per person, they apparently have not had much of an impact on the proportion of people living in denser neighborhoods. What does seem to work are conservation programs. Funding for such initiatives seems to be a very strong indicator that a city is densifying. “Cities with any level of conservation funding are denser than cities with no conservation funding,” the authors report. Though they have no data to explain why this is, they do have a few reasonable guesses. It could be that the conservation money sets some land aside for parks. Or maybe people who live in cities that invest in conservation are willing to live in denser neighborhoods.

Overall, many of America’s cities are finally curbing their seemingly insatiable appetite for land, but many have a long way to go before they begin to look like New York or San Francisco. Most of the land within American cities is locked up in low density development, which houses a relatively small number of people. So long as the desire for such housing exists, cities will continue expand.


McDonald, Robert I., Richard T. T. Forman, and Peter Kareiva. 2010. Open Space Loss and Land Inequality in United States’ Cities, 1990–2000. PLoS ONE 5: e9509. DOI: 10.1371/ journal.pone.0009509

Photo by opacity.