A few anti neighbors aside, Fairfax County leaders and advocates broadly agree with the goal of transforming our nation’s largest and most successful suburban office park district into an urban city, where most residents and workers travel in ways other than single-passenger vehicles. But nobody has done this before on such a scale, and there is less consensus on how, exactly, to achieve the vision.

A Tysons task force has spent years developing a plan for a city with 113 million square feet of development, with four high-density districts centered around four Metro stations and four other, lower density districts farther out that transition to the adjoining suburban neighborhoods.

It’s a compelling vision, but acolytes of traditional traffic modeling worry. Their models show that the traffic generated by this level of development would overtax existing roadways, and Fairfax County staff therefore concluded that the plan couldn’t succeed without new exits off the Beltway and new collector-distributor lanes on the Toll Road.

However, traditional traffic modeling also has its flaws. As Congressman Gerry Connolly noted recently, we can only imagine what Pierre L’Enfant’s traffic modelers would have said about his crazy idea to build a city along the Potomac, had he proposed it today.

We have living proof that cities much larger than Tysons can exist; Arlington did it with the Rosslyn-Ballston corridor. Tysons will be far larger, about the size of the L’Enfant Plaza/Navy Yard area of DC, according to COG. The question is how to create the reality that should be possible in a place that’s far more car-dependent now.

Last month, Planning Commissioner Walter Alcorn proposed cutting the plan in half temporally, developing about ¾ the proposed density in the next 20 years instead of planning for the full 40. Alcorn’s plan would also eliminate set density maximums, instead having Fairfax planners and the Board of Supervisors evaluate each proposal as the developers applied for them.

The Sierra Club endorsed Alcorn’s plan, arguing that the full Tysons requires more and better transit than just the Metro stations, and the exact nature of that transit and financing for it is not yet clear. They prefer the shorter planning horizon to ensure that the transit to the periphery, and from other parts of the County to Tysons besides just the east-west Silver Line, get built.

On the other hand, the Audubon Society advocated for a complete plan. In her testimony at a recent hearing, Audubon’s Stella Koch said,

Unlike many plans where a piecemeal approach may work, Tysons Corner redevelopment is different.  This plan must be implemented as a whole or it falls apart.  Without the internal grid of streets, transportation inside of Tysons does not work.  Without an integrated network of sidewalks and paths, and inviting shops and storefronts, people do not want to walk to destinations. The Tysons Vision must be implemented as a whole.

Developers with parcels farther from Metro stations say the change would chill development, “particularly in the non-transit oriented development areas. However, development in the non-transit oriented areas are precisely those that will generate the traffic that people are worried about.

Making those landowners wait longer, until the city grows in a way that facilitates good transit to the parcels, makes sense. On the other hand, many landowners have been waiting for this Tysons plan to build; it’s also possible they’ll just build a strip mall or other auto-intensive land use that will be harder to replace in 20 years. As Koch wrote, “If insufficient density allotments in the four outlying parts of Tysons induce by-right development and the lack of contribution to the grid of streets or any other part of the plan necessary to the success of Tysons, the plan fails.”

A big part of the plan, and reasons environmentalists like Koch are so excited, is that it makes the property owners invest in substantial amenities. There’s the street grid, which everyone agrees is essential, state-of-the-art stormwater management, transit, streetscapes and more. The Alcorn plan could focus Tysons growth around Metro stations first, but it could also cut out profitability enough that Fairfax won’t be able to get these amenities.

Moreover, Alcorn’s proffer-by-proffer approach makes it more likely the urban vision will become compromised in the future. We have a lot of suburban sprawl because it’s often politically the path of least resistance. It’s hard to insist on no development, because a property owner pushes hard for the right to build, but also hard to allow denser development, because the volume of neighbors’ objections seems exponentially (or at least geometrically) related to the nearby density.

The ideal Smart Growth design for a city would have no development in some areas and more development in others, but that’s really hard to implement when different property owners own each piece, as we saw with the Great Seneca Science Corridor (formerly Gaithersburg West, aka “Science City”). Therefore, most of the time, you end up with low-density development spread evenly, which from an urbanism, transit, and environmental point of view is the worst kind.

If the Fairfax County Planning Commission and Board of Supervisors have to debate each development one by one, it’ll be tempting just to cut each one down a little, then the next a little more. Each decision might sacrifice a small amount of amenities, but that would be like boiling a frog slowly, where the frog doesn’t notice until it’s dead. With a larger plan, we can see how many amenities are or aren’t there all at once.

This is all very tricky because Fairfax is trying to build a city not from nothing, not in the pre-auto age, but today. We know that wonderful cities can exist today because we have some, like Washington, DC. But Washington grew very slowly. The L’Enfant Plan only covered a small area, and even most of that wasn’t filled up for many, many years. Building cities a bit at a time worked.

However, that happened during the pre-auto age. Cities grew from the center outward because transportation required it. Streetcar lines accelerated growth, but only along key corridors. Most land stayed agricultural because it was too hard to get to. Also, zoning didn’t even exist to limit what could be built near the transit stations or downtown. Today, we can nearly instantaneously convert hundreds of acres into strip malls and housing developments, and residents fight everything. That means that without a good plan, everything can fill up with sprawl in the blink of an eye.

Is it better to plan out a complete city now, even though some of the transportation elements aren’t fully fleshed out? Maybe necessity will force a solution, or maybe traffic will just cripple everything. Or is it better to start smaller and go from there? Maybe that will create a better city, or maybe it’ll just forego the chance to build one at all. Good organizations are coming out on both sides of this issue.