Densifying Transit Corridors Is Not Densifying Enough

Curitiba

One recent urban planning trend advocates for so-called “Transit-Oriented Developments”, or TODs. This is when cities allow already built-up areas to increase development along mass transit corridors, such as bus or rail lines. If such transit infrastructure didn’t exist, the potential development increase in these areas would be restricted.

The TOD idea is mainly based on the Curitiba model, a city that allowed denser building and populations along Bus Rapid Transit (BRT) corridors. The above image shows the effects: high-rise buildings with minimum or absent setbacks along the corridors, and sharp decreases in density on adjacent streets, since these latter streets would theoretically use the BRTs less.

The same logic is being applied for São Paulo’s new recently-approved Zoning Code: sharp density increases in allowed built-up areas along mass transit corridors, and more low-slung buildings further into the neighborhoods.

This TOD model is certainly better than previous ones, wherein dense development was restricted altogether, even when near mass transit. As I’ve previously noted, lower densities undermine the economic feasibility of transit networks, which rely on intense agglomerations. Many factors justify TODs’ attractiveness to current planners, including that they make transit viable, increase the centrally-located housing stock, and satisfy residents of low-rise areas, who usually enjoy keeping their neighborhoods’ original features.

But I haven’t become a broad advocate of TODs because they disproportionately favor these low-rise residents, disregarding everyone who must be pushed into suburban peripheries. A TOD-driven approach has a correct logic of analyzing neighborhood scale, and trying to organize it likewise, based on transit and street availability. But it doesn’t account for the factthat every unit left unbuilt within a neighborhood will necessarily be built in the outskirts, generating longer commutes and higher infrastructure costs. Peripheral residents certainly are not the same as downtown ones, but they would still benefit from living in central locations that they are now priced out of.

So how would densification work inside neighborhoods not directly served by mass transit?

Keep in mind that allowing denser development does not mean all neighborhoods will suddenly become hyper-dense. Some regions are more attractive than others, and redevelopment costs are higher in neighborhoods already filled with 8- and 9-story buildings, such as the areas suggested for more density in São Paulo’s new Zoning Code. For redevelopment to occur, the demand for housing must surpass all transaction costs – meaning there would already need to be enormous pressure to occupy the area previously restricted via regulation.

Image of São Paulo’s Zoning Code diagram, representing the maintenance of heights and densities inside the neighborhoods.

Less-demanded neighborhoods will not receive such development, remaining available for those who prefer less intensive or cosmopolitan features. When considering a city’s dynamics as a whole, we should keep in mind that lower-density options will always be available, even if a little more distant from central zones. But the person demanding a less urban lifestyle should be the one to endure this distance trade-off, not the other way around.

Critics frequently claim that dense development would lead to greater motorized traffic congestion, but I disagree. As such areas become more viable for walking and transit, the need for personal car use would decrease on a per-capita basis.

Lastly, while such upzoning certainly transforms neighborhood characteristics, that transformation is just part of urban life. We should remember that no city or building would exist – not even the 8-story ones São Paulo intends to preserve – if its first inhabitants had shut out new neighbors on behalf of preserving their lifestyles. City life is, by definition, the life of dense human agglomeration of people.

[Originally published on the blog Caos Planejado]