A new report explains exactly how.

The core problem of creating sustainable cities is as well-known as it is tricky. On the one hand, everyone who's thoughtful about urban sustainability admits the environmental, economic, and social problems of sprawl and auto-dependency. On the other hand, everyone who's realistic about the situation must admit that people are crazy about their cars and pretty keen on low-density, single-family homes, too.

Most of the modern attempts to reconcile this problem, at least in U.S. metropolitan areas, create more problems of their own. Smart growth initiatives to increase densification, reduce car use are often met with vehement objections — some irrational, some genuine — on the grounds of personal choice. Often these efforts are simply ignored by local government. Meanwhile, promoting livability through public transit can run into financial and political hurdles too tall to overcome.

For these reasons and others, Mark Delucchi and Kenneth S. Kurani of the Institute of Transportation Studies at the University of California-Davis aren't so sure we're going about these solutions the right way. They believe that car ownership is so desirable that any effort to address sustainability must embrace it, rather than defy it. They also believe that what's so pernicious about modern sprawl is not the cars themselves, per se, but their "high kinetic energy" — in simple terms, their size and speed.

So, in a fascinating-if-fantastical paper set for publication in the Journal of Urban Planning and Development, Delucchi and Kurani propose a radical concept that would let people have their suburbs and cars and their sustainable cities, too.

The key to meeting this challenge, they argue, is creating brand new communities around a "dual roadway system." There would be one "heavy" road network connecting cities that accommodates conventional cars. And there would be another "light" road network, reserved for low-mass low-speed alternatives for local travel. As they put it:

Much that makes our present systems of automobility unsustainable is attributable ultimately to the high kinetic energy and ubiquity of fast, heavy, motor vehicles. The challenge is to find a way to dramatically lower the kinetic energy of personal travel while sustaining the advantages of personal, self-directed mobility and access to both urban and suburban living. We believe that one way to accomplish these is to create two autonomous and universally accessible travel networks: one for fast-heavy vehicles, the other for low-speed, low-mass, transportation modes, including new designs of motorized vehicles.

In other words, it's time to redesign residential living as we know it.

Delucchi and Kurani go into great detail about their hypothetical new towns, but the basic gist works like this. People would live in small city clusters built around a town center replete with stores, offices, schools, public buildings, and parks. Traveling around town, residents would take the "light" road network. They would walk, bike, or drive tiny cars incapable of exceeded 25 mph. There would be no on-street parking at all. The general idea is to promote interaction and accessibility.

Conventional cars would travel the "heavy" road network out of town, mostly to commute elsewhere for work or shop at big box stores confined outside the city limits. (A few "heavy" roads would lead into town, largely for commercial deliveries, but these roads would never intersect with the "light" network.) Multi-family residential buildings would be situated closer to the center, with lower-density single-family units constructed toward the outer fringe. The towns themselves would be limited to populations of 50,000 to 100,000.

They would look a little something like this:  

The benefits of this dual transportation existence would be considerable, according to Delucchi and Kurani. Safety would improve dramatically, with fatal crashes all but eliminated on the "light" network. Mobility would improve — particularly for the young, old, poor, and non-drivers. Public intercity transport would also be a breeze: just head to your town's rail station, hop the train to the next town, and rent a "light" vehicle to get around. Congestion would improve with traffic spread across two road networks. The environmental impact of the system would be lower, with reduced emissions and a longer infrastructure lifecycle. A sense of community often divided by interstate highways would be recaptured, too.

All this for a price the researchers believe would be similar to what we pay for suburban road networks right now. That's because the "light" road would have low capital costs and no traffic lights, and the "heavy" network would be less extensive. Additionally, there would be far fewer public transit costs, with only a few options to help those who can't navigate the "light" network on their own.

Delucchi and Kurani call their idea "novel," but they recognize that a handful of communities out there that already embrace many of its key components. The Palm Desert community in California, for instance, has a "light" road network that residents traverse on foot or via golf carts. Village Homes in Davis, California; Radburn in New Jersey; and Houten in the Netherlands also have something similar to dual transport systems — the latter coming closest, with its bike network around town and car-only beltway outside it.

At the same time, the relative novelty of this bold idea may speak to its many flaws. For starters, in the United States, the political obstacles of encouraging such a community would be overwhelming, and the financial ones might be, too. (Even if you buy the favorable back-of-the-envelope calculations on transport cost, the price of land acquisition would be enormous.) Beyond that, the system essentially abandons public transit for personal vehicles — and arguably households would need to own more vehicles, in this world, so everyone can get around town.

But the real impossibility of the concept lies in its psychological barrier. The biggest problem with conventional ideas about suburbia and car ownership, after all, is that they have become the conventional ideas about suburbia and car ownership. If places like Radburn and Houten were so popular, we'd all live in Houten and Radburn. Delucchi and Kurani ask us to embrace the concept of a car to address urban sustainability, but since "light" vehicles don't fit that concept anyway, we still must redefine what they hope we'll embrace.

"In this sense, behavioral and institutional inertia may be the greatest impediments to implementation," the researchers acknowledge, toward their paper's conclusion. To be sure, there's an attractive logical simplicity to their proposal, and there are elements within it that planners and concerned residents should consider much more closely. But if the problems of urban sustainability had an easy answer, we probably would have already found it.

Top image: <a data-cke-saved-href="" href="" "="">Tim Roberts Photography/

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