Uncontrolled urban growth is probably the greatest obstacle to sustainable development in the United States. Cities are spreading all over the natural landscape far faster than population increases or economic progress require, while older urban districts with their valuable infrastructures are underused or abandoned. 32

Many aspects of current development policies and practices work contrary to the goals and tenets of sustainable community development. Much of this can be traced to this nation's reliance on the private automobile as the dominant form of mobility. (One can argue that the very popularity of the car is based in our national psyche and our inherent distaste for cities, crowding and inhibitions on personal freedom; this, however, does not belie the limitations of natural resources or the inefficiency of the auto-based system). Land use policies, zoning regulations and building practices naturally grew to reflect the capacities and characteristics of the auto-based system; these policies, regulations and practices have now been reified throughout the country. Advocates of sustainability, however, suggest that we work, now while there is time and energy, to balance our reliance on the private automobile with other, more sustainable practices and policies.

The most important elements of these practices and policies are summarized here as a series of principles: general statements describing the backbones of a "theory" of sustainable community design, with particular focus on those aspects that directly and indirectly involve transportation and land-use.

1. Implement policies to make drivers pay the full cost of using personal automobiles.

As has already been discussed, drivers today pay only a small percentage of the full costs of using an automobile. The costs of externalities such as pollution control, road construction and maintenance, damage and loss of life due to accidents, maintaining the infrastructure necessary to supply petroleum, and so on, are not represented in the price at the gasoline pump. Until they are, the general public will not respond to incentives for more sustainable development; the alternatives will be more appealing and less economically expensive.

Paul Hawken recommends a thirty-year phase-in of full-cost pricing. Other authors recommend incremental increases of a certain percentage per year, or of a fixed monetary amount (de, $0.20 per gallon per year for twenty years). Monies gathered from the increased costs should be dedicated to implementing any of a range of sustainable policies or projects.

2. Except in the most densely built-out areas, limit building beyond the edges of current development.

Building on untouched sites always destabilizes natural systems and can mean losing valuable agricultural or forest land. Access to the new development requires more roads, more trips, more extensions of the urban infrastructure; in other words, more natural resources used and pollution created. 33

Optimal use of developed land, balancing of developed and undeveloped areas, integration of functional open space with development, and the creation of clearly defined communities are all fundamental tenets of sustainable community design. Leap-frog development and suburban fringe development both work against this principle. As long as development continues to sprawl outward at the edges, engulfing agricultural areas and other undeveloped lands, there is little incentive for high-quality, mixed-use development within the developed area. The areas of many contemporary communities increases far faster than the population. With lower densities, these communities become more auto-dependent, and there is even less chance that mass transit of nonautomotive transit can be effective.

Placing a moratorium on piecemeal, low-density, mono-functional development at the edges of built-up areas promotes an increase in density among selected developments and the gradual integration of uses as a means of better tapping the development potential of different locations within the already-developed areas.

From a biological perspective, modern cities and suburbs resemble the noisy, crowded bird colonies scattered on offshore islands and rocky coastlands across the globe. In the animal kingdom, colonies are a fairly sustainable way of life, providing two basic conditions are met. First, colonies can persist, even thrive, if the demand for resources by the inhabitants does not exceed the supply readily available from surrounding areas. Second, colonies can be sustained if the waste they produce does not poison its inhabitants.

Like bird colonies, cities and suburbs draw heavily on the resources of the surrounding environment. What was once a relatively small stream of resources flowing into early cities, however, has in this century become a deluge. To satisfy resource-hungry human colonies, land is often stripped bare or trampled, or overgrazed, soil is subjected to erosion, and farmland is transformed into desert. Cities and suburbs also produce sizable amounts of waste. Air pollution, hazardous waste, sewage sludge, garbage, and other wastes pour out of our cities, far in excess of the environments s ability to assimilate them, threatening not only the health of urban inhabitants but the health of the entire biosphere.

The problem with human colonies is that they violate the conditions required for sustainability. Metropolitan areas are out of balance with the environment upon which they depend . . . The ever persistent spread of cities will continue to devour valuable farmland, forests, and pasture. Gobbling up land and polluting the water and air upon which all life depends, our cities are on a collision course with the future. (9)

3. Re-develop vacant or low-intensity development within currently developed areas at higher intensities.

Redevelopable and infill sites should develop under utilized parcels with new uses that allow them to function as walkable, mixed-use districts. Existing uses which are complementary, economical, and physically viable, should be integrated into the form and function of the neighborhood. Existing low-intensity and auto-oriented uses should be redeveloped to be consistent with the TODs (transit oriented developments) compact, pedestrian-oriented character 34

Every project that is built using under-developed or previously developed land within built-up areas is one less project that will replace virgin land. Incentives to turn farmlands, wetlands, habitats and other open spaces into sub-divisions will diminish, and these uses will remain functional, increasing the diversity of the land-uses found in a region

In addition, much of the development that has taken place in the past thirty or forty years tends to be deliberately isolated, monofunctional and auto-dependent. Approaching such developments as areas for potential re-development helps foster increased diversity of uses, greater connectivity of functions and higher residential densities. All of these factors make non-automotive mobility options increasingly workable.

Doubling residential or population density reduces the annual auto mileage per capita or per household by 20 to 30 percent. Consequently, if the population of an area doubled wholly by infill its VMT would likely increase only by 40 to 60 percent, rather than the 100 percent it would increase if the city grew in its present form.
-- John Holtzclaw. Explaining Urban Density and Transit Impacts on Auto Use, page 25.

Redevelopable and Infill Sites.

4. Design comprehensive, mixed-use neighborhoods instead of isolated pods, subdivisions and developments.

Assuming that the prudent expenditure of our limited funds will prevail for the foreseeable future, each dollar we spend must create a corresponding marginal benefit. For example, our plans for environmental protection must sustain our inner cities and provide for the cost-effective development of open-space and farmland. Further, maintaining and improving our existing urban infrastructure should result in lower unit costs compared to the higher costs associated with suburban economic development. 35

Neighborhoods and other "natural" forms of community tend towards particular physical dimensions and populations. Too often in contemporary sprawl development, neighborhoods that began as distinct elements gradually crush together into a collection of functionally isolated but proximate "pods." This tends to increase the inefficiency of hierarchical road systems and to promote further social isolation. In many instances, such low-density sprawl creates the paradoxical situation in which every single-family house has a large (decorative) front yard and a more functional backyard, but there are very few functional, easily accessible public open spaces.

Today's units of development are no longer one or two buildings; instead, development proposals range in size from ten to twenty-unit subdivisions to entire Master Planned Communities of ten- or twenty thousand people. Even the incremental units of a large-scale development are themselves large, often covering several hundred acres. And, while the economics of today's development often mitigate against piecemeal commercial and office development, it is precisely these functions that can most increase the sustainability of residential areas. A one-hundred acre neighborhood is walkable only to the extent that there are functional destinations at the center of the neighborhood and that the streets and paths of the neighborhood are designed to be pedestrian friendly

The economies of scale and the nature of corporations today mitigate against the small "mom and pop" stores that are so appealing to advocates of sustainability. On the other hand, more and more communities within the United States are drawing a line with respect to the destruction of their historic cores at the whims of large retail developers such as K-Mart, WalMart and others. The economies of scale are still subject to the idiosyncrasies of particular jurisdictions and as the operational profit-margins of certain types of retail establishments are pared down, there is increasing opportunity for small-scale, localized "boutique" stores. It has been predicted by some retail analysts that within a few years, most shopping will take place in one of two venues: enormous blank-wall, big-box warehouse markets at the outskirts of a community, and in small neighborhood scale convenience shops. The entire middle-range of the retail market, up to and including the traditional post-War malls, may disappear.

Fig. 18: Integrated vs. Segregated Community Design

The spaces between neighborhoods and between communities should consist of functional open space. These can include farms, grazing areas, gardens, parks, playgrounds and the like. Because these open boundaries will, of necessity tend to be long and linear, they make ideal locations for jogging trails, greenways and bicycle paths; essentially, they comprise an alternative transportation route for residents within adjacent neighborhoods.

A finer grain separation of uses within buildings, neighborhoods, and communities can help support a more time- and energy- efficient life style and can create more vital and diverse places to live. 36

Fig. 19: Comparative Analysis of Neighborhood Street Patterns.

That a city should be an aggregate of distinct but fundamentally similar parts, as a living organism is made up of cells, has been an understood idea of contemporary planning. Otherwise the vast modern city seems too huge and shapeless to grasp - not just for the citizen, but more important perhaps, for the planner herself Everyone should live and work in some small, bounded area, in which she will feel at home.
-- Kevin Lynch. Good City Form, page 400.

The grain of a settlement is another fundamental feature of its texture, a feature often confounded with density. By grain I mean the way in which various different elements of a settlement are mixed together in space. These elements may be activities, building types, persons, or other features. The grain is fine when like elements, or small clusters of them, are widely dispersed among unlike elements, and course when extensive areas of one thing are separated from extensive areas of another thing.

-- Kevin Lynch. Good City Form, page 265.

5. Make neighborhoods as pedestrian-friendly and as bicycle friendly as possible.

The easier it is for residents to walk or bike around their neighborhoods, the more likely they will avail themselves of these forms of mobility. Streets within neighborhoods should be interconnected to form a network; this makes it possible to take a variety of routes to get to a particular destination and serves to lessen auto traffic on any one route. With less traffic on individual streets, people will be more inclined to use these street for biking. Streets should be narrower than is customary, and should make provisions for on-street parking. Narrowing the through-way provides more room for sidewalks and bike lanes, and helps slow down moving traffic. On-street parking reduces the need for parking lots, and parked cars serve as a barrier between sidewalks and the street itself.

Neighborhoods should include systems of public open space --parks, playgrounds, etc-- and these should be integrated with the walkways and bike-paths. Neighborhoods should include commercial centers and a variety of public and civic uses: churches, schools, etc. These should all be integrated with the pedestrian and bicycle systems, and should be made as accessible as possible.

Street designs need to take into account the needs of cyclists and pedestrians. All city and urban streets need sidewalks for people who are on foot. The effectiveness of bicycle paths and lanes depend on their giving cyclists and drivers equal access to various destinations - not as often happens, relegating cyclists to out-of-the-way routes so that motor vehicles can have free reign. 37

Pedestrians and bicyclists should have priority. Mass transit should be efficient and available, and private automobile use should be discouraged. 38

6. Create mass transit systems to link neighborhoods, employment centers and other "nodes."

In an energy efficient city, there would be a higher density of development along bus routes and around railway stations instead of an energy-consuming spreading pattern of development. 39

Mass transit systems should link different neighborhoods and should link neighborhoods to employment and commercial centers. To the degree that neighborhoods themselves can contain a wide variety and scale of uses, there will be a high-rate of "internal capture." However, mobility outside of neighborhoods should be provided by one or more mass transit alternatives. These can include busses, vans and group taxis as well as in-ground systems such as light rail, commuter rail and/or heavy rail.

Fig. 12: Transit Oriented Development (TOD) Transit Stop.
To optimize the efficiency of a mass transit system, intensify development at and around system stops. Make sure that major destinations are within a quarter-mile radius of the stop itself, and design the transition between stop and destinations in keeping with pedestrian friendly design principles.

7. Create communities that contain the full range of development densities and land-uses; avoid large tracts with the same density or land-use

Advocates of sustainable communities are not simply concerned with a reduction in energy-consumption and decreasing pollution; part and parcel of their theory is the search for more economically and socially integrated communities. Good examples of this are few and far between today in a climate in which the dwelling is regarded first and foremost as an economic asset rather than as part of a social fabric. In our increasingly mobile society, where the average family moves every five years, houses have become a form of monetary hedge against inflation. The primary way to maintain the value of the home as an investment is to guarantee the stability of the surrounding neighborhood. To do this, many developers create entire projects of the same type, style and cost of residence. While potentially useful for economic stability, such environments tend to create artificially striated communities whose demographics bears no resemblance to that of the country as a whole or even to the region within which the development is found.

This situation, sometimes referred to as "forting," is neither functionally efficient nor is it socially advantageous. By basing the structure of a community on exclusion rather than inclusion, one is forced to create redundant servicing systems, and one heightens social disparities and incites negative rather than positive interactions. While the implications of this are not directly tied to sustainable design, the implications for a socially integrated community versus one that is economically striated are important.

Fig. 22: Local Street: Medium-to-High Density Neighborhood.

Fig. 20: TOD Transit Stop.

Clustered dwellings are much more efficient in their use of facilities by sharing amenities like swimming pools and play areas. More importantly, if well planned, they can reduce urban distances and bring dwellings closer to places of work, shopping, and schools. Higher densities make walking, bicycling, and mass transit much more feasible modes of transportation, thus reducing the use of automobiles and consumption of energy.

-- John Tillman Lyle. Regenerative Design for Sustainable Development, page 124.

What people seem to dislike most about high density is the auto traffic associated with it. The problem suggests the solution. By converting a significant portion of the space resources taken by the automobile to other land uses, the population density can be raised significantly while reducing the negative impacts of density. Urban space hasn't been considered a resource, so a space wasting transportation system - the auto - has been substituted for a space-conserving system.

-- Bob Walter, Lois Arkin and Richard Crenshaw. Sustainable Cities - Concepts for Eco-City Development, page 171

The draft Plan seeks to reduce the use of single occupant vehicles (SOVs) . . . Noting that there are more registered vehicles in the City than residents and that errands and leisure trips outweigh work trips by a four-to-one ration, the document calls for more convenient transit and higher-density land use development... the Plan promotes four types of urban villages...

1. Urban Center Villages built around regional transit, emphasizing mixed employment and high density housing (up to 50 dua and 50 jobs per acre).

2. Hub Urban Villages contain mixed-use core areas with moderate density housing (812 dua) on the periphery;

3. Residential Urban Villages, primarily residential (1015 dua) but also with complete retail services, and;

4. Neighborhood Villages with lower densities (8-10 dua in the core) and a 2-3 block commercial center area with direct transit access.

Within each neighborhood, a new system of personalized frequently-circulating local transit vans would be developed to supplement direct transit between village centers. These LINC (Local Initiative for Neighborhood Circulation) vans would circulate every 12-20 minutes during peak hours, with additional dial-a-ride service available at all times...

-- Andrew Young. Sustainable Development in Seattle.


© 1994 Center for Urban Transportation Research