More People, Less Driving: The Imperative of Curbing Sprawl

Experience with case studies has made it clear to many urban
planners and environmentalists that to maximize the benefits of transit
investments, and to slow growth in traffic congestion, vehicle miles
traveled (VMT), and carbon emissions, you have to focus on land use.

sprawlComp.jpgPhoto: Penn State.

knowledge has begun working its way into the policymaking world, to the
extent that local and state legislatures are beginning to craft rules
that explicitly factor the carbon impact of land use effects into
decisions about new development and infrastructure construction. In a
few years time, the federal government may follow.

But there’s not as much in the way of hard studies of the
effects of land use as we might like — mainly because it’s been a
non-issue, so far as most of the country is concerned, for much of
recent history.

Aiming to address this (and acting under a
congressional mandate), the Transportation Research Board recently
completed a study that has now resulted in a very large report: "Driving and the Built Environment: The Effects of Compact Development on Motorized Travel, Energy Use, and CO Emissions."

report is actually five mini-papers, and at nearly 200 pages long it
makes for a lot of reading. But the findings reported in the
introduction give an idea of what it’s all about.

The authors
conclude that compact development is likely to reduce VMT: "The effects
of compact, mixed-use development on VMT are likely to be enhanced when
this strategy is combined with other policy measures that make
alternatives to driving relatively more convenient and affordable." No
surprises there.

Finding No. 2 is: "The literature suggests
that doubling residential density across a metropolitan area might
lower household VMT by about 5 to 12 percent, and perhaps by as much as
25 percent, if coupled with higher employment concentrations,
significant public transit improvements, mixed uses, and other
supportive demand management measures."

They note that were
you to move the residents of Atlanta to an area built like Boston,
you’d lower the Atlantans’ VMT per household by perhaps 25 percent.

land use results in reductions in energy use and carbon emissions, the
authors report, from both direct and indirect causes. (Direct causes
would be a reduction in VMT; indirect include things like longer
vehicle lifetimes from reduced use and the greater efficiency of
smaller or multi-family housing units.)

But one of the crucial pieces of data included in the report is this:

many as 57 million new housing units are projected to accommodate
population growth and replacement housing needs by 2030, growing to
between 62 and 105 million units by 2050 – a substantial net addition
to the housing stock of 105.2 million in 2000.

of smart growth efforts or rail and transit investments often wave off
the potential gains from building differently by noting that so much of
the current housing stock is of the sprawling, single-family home,
auto-oriented sort. Convincing the people who currently live in such
places to give that up for something different, they say, is sure to be
an extremely difficult sell.

But that’s not the issue. No one
is suggesting we rip down all of suburbia. Rather we, or at least I, am
pointing out that between now and mid-century, the country will very
nearly have to build itself all over again to accommodate population
growth. In addition to the 100 million homes now in America, somewhere
between 62 and 105 million more will be built.

The critical
question is what the balance of that new construction will look like.
The TRB report suggests that if 75 percent of this new construction is
of a more compact variety, that emissions could be reduced 10 percent
or more from the baseline scenario (and that is not taking into
consideration the deployment of cleaner electricity generation and
other potential sources of savings).

Ed Glaeser argued
— and this is kind of hard to believe — that land use shifts from
building high-speed rail between Dallas and Houston would not provide
much in the way of benefits, since, he guessed, only 100,000 or so
people in each city would move from the suburbs to the central city.
But this entirely misses the point.

Houston and Dallas may each double their current housing stock between now and 2050. Where are those homes going to go, with what climate impacts? That’s the critical question.

shifts and changes in energy prices are sure to encourage some
households that are currently living at low densities to move to more
compact developments, and that’s a good thing. But that’s not the main
reason to begin focusing on the significant available savings from
smarter land use decisions.

The main reason is the growth
that America will continue to face. It’s difficult to imagine that the
nation can double its housing stock while building in a sprawling
fashion without facing major environmental costs and economic
difficulties. Land use patterns will need to change. And as this report
documents, there will be considerable advantages to facilitating that

  • “Driving and the Built Environment: The Effects of Compact Development on Motorized Travel, Energy Use, and CO Emissions.”

    Already out of date. For $50,000 in capital investment, we can deliver a box of groceries to any house in any suburban sprawl using deliver bots for a $1/box.

    Let us try a thought experiment. If we abandoned a suburban neighborhood, leaving the houses vacant, what is the cost of delivering groceries to the occupants? Zero, no occupants. Now, add two occupants in the neighborhood with no cars, what is the cost of delivery? $5/box. This time, no cars, no humans driving on the roads in suburbia. Now add eight more residents, with no cars and delivery cost drops to a $1/box, again no cars on the road. Now add another hundred residents, with cars, and the cost goes up to $20/box? Why? Because of fear that the robots cannot work around cars. Yet if you remove the cars, residents have no fear that robots will drive on the lawn and ruin the shrubs.

    The problem of suburbia is fear, fear that robots and human cars do not mix, nothing more. The actual, real cost of suburban sprawl is quite small in an automated world.

    Yet, take an urban environment, much more activity, many more pedestrians. What is the fear that a BRT bus running on automatic lane guidance will cause a problem? Zero, very little fear, with or without human monitoring, automated lane guidance for BRT is nearly accepted across the world.

    I looked through this study, it is nonsense now, though not nonsense three years ago. Such is technology. Suburban sprawl will continue and increase because robotic delivery, cyber cabs, deliver bots make is so cheap to live in suburbia.

  • DJB

    The critical thing here is to try and convince people to live more densely. Real estate development in America is mostly driven by the private sector (in the context of public regulations and subsidies). In the end, we won’t get policies that promote density and we won’t get developers who will build densely without more buy in from regular folks (i.e. as voters and consumers of housing).

    To convince a skeptic, you have to start by addressing his/her objections. What are these objections likely to be? Affordability, open space, crime, traffic, homeownership, noise, etc. In my opinion all of these issues have urban solutions, but I’m not the person you have to convince.

    Don’t get me wrong. I’m a huge advocate of dense, mixed-land-use development. I live in it, and I speak out for it. I’ve seen with my own eyes what it can do for transit and walkability. The potential is truly breathtaking.

    How can you convince people, who, for very human reasons, are skeptical, hesitant, and curious? (Don’t hold out on telling me if you know, because I don’t).

    How do you make the middle class norm a condo in a 3-5 story building instead of a detached single-family house? I think this is the central question faced by American planners who care about sustainability in the 21st century. I don’t even know if it’s possible, but it’s damn sure worth a try.

  • John Boucher

    Comical. Build densely and pray people don’t drive. Does anybody really believe that one always has something to do with the other? And I’m sorry, but isn’t energy production the big contributor to global warming here? And wouldn’t increased density, and therefore higher energy use in the new human warrens of condos and shops, outweigh the effects of less driving. That is, of course, should less driving actually occur.

    Can’t we just say this is all a sop for the building trades folks and realtors and have done with it? Low (and no)emission cars are on the way. And when they are here and no longer doing quite so much damage, will all those high density condo jungles will be in place to take up the slack? If the pay to play crowd in Sacramento have their way, that answer is yes. The new United States of Coirporate Generica. With low flow toilets.

    I can’t believe people have bought into this big lie.

  • DJB

    A tale of two LA zip codes from the 2000 Census:

    90057 – 44% of workers take transit to work (I shit you not), 70% of the housing units are in buildings with 20 or more units.

    90036 – 4% of workers take transit to work, 36% of the housing units are in buildings with 20 or more units.

    I’m not saying residential density is the only factor to consider in transit ridership (that would be an extreme oversimplification). I’m just saying there are already lots of people riding transit in dense neighborhoods in LA now. Ignoring that evidence seems like a mistake.

    Check the numbers for yourself:

  • DJB

    I really think this is a worthwhile topic John, so I’ll address your arguments briefly, one by one, in a spirit of friendly argumentation.

    This is why it’s reasonable to assert that people will drive less per capita (nobody said they’d all stop completely, even Manhattan has drivers) in a dense neighborhood that mixes land uses:

    1) More people per unit area means more businesses can be supported per unit area, which means the average distance people have to go to get to the nearest business goes down. This means they can more easily walk, bike, or take transit, or, if they do drive, they aren’t going as far on average, which does indeed mean less driving per capita.

    2) Density means more people are in an area to support the transit system and transit service can be upgraded (either to higher frequency or from bus to grade-separated rail). One of the main reasons people don’t ride transit is wait times and density takes on this issue directly.

    3) Density makes it easier to promote a market for parking. When parking is priced, people use less of it, which means they drive less.

    Energy use in construction:
    Of course building density takes energy, so does building suburbia. You have to take a long-term view of the situation and realize that the energy use will be offset over time as people drive less.

    “Clean” Cars:
    Cleaner cars are important, but it’s highly uncertain whether they can become widespread enough to address transportation GHG emissions effectively in the short-to-medium run, especially in low-GDP countries. All highway-capable cars currently sold in the U.S. at reasonable prices run on gasoline (and a handful run on natural gas). The new hope, the Chevy Volt plug-in hybrid, is supposed to cost $40,000 (assuming it really comes out); not exactly affordable for most people. Even if a few people buy them, how much of a dent will that really make? Plus, no matter how a car is powered, it’s going to add to traffic and it’s a threat to truly clean transport: walking and biking.

    Corporate Greed:
    Realistically, some people stand to make a fortune from density, but other people stand to make a fortune from building new suburbia (and the cars it makes inevitable, and the gasoline that powers them) as well. Pick your poison.

  • cph

    “90057 – 44% of workers take transit to work…90036 – 4% of workers take transit to work”

    The income discrepancy between the two zip codes (90057 is low-income Westlake, while 90036 is high-income Park La Brea) might overshadow density, in terms of the difference in transit use between the two areas.

    (Any high-income areas in LA County with a good level of transit usage?)

  • DJB

    I just thought of the perfect neighborhood.
    90024: Westwood

    Median Family Income: $90,000 ($40,000 for LA)

    25% OF PEOPLE WALK TO WORK! 4% is the city average.

    Westwood is much denser than the city average and very mixed-use: 55% of the housing units are in buildings with 20 or more units (24% is the citywide average) and 14% of them are detached single family (39% for LA city).

    And of course, this ignores most of the huge student population, which is largely unemployed and walking and biking to class at UCLA.

    I know you asked for a transit example, but I think I like this one even better :)

  • Walking is a seriously underrated form of transit.

  • I’m always amused, and outright astonished, that all of these “studies,” “urban planning wish lists,” and “sustainable ideologies,” collide directly into the reality of America.


    I hate to say it, but the dream of urban, and other alternative based travel, is but a Utopian side-story.

    The people, by and large, who use Mass Transit, don’t own cars.

    Although, sad it’s true.



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