Questioning density

Did they get it right?

This blog tends to applaud urban density, deeming it essential to healthy, sustainable neighborhoods. Density is often defined by the amount of people occupying a square mile (or acre, or hectare). But what is the ideal level of density? How can that be objective rather than subjective? Is there a tipping point where you can have too much density? (Above is infill mixed-use construction at the corner of U Street and 13th Street in Washington, DC, a city with roughly 9500 people per square mile. Compare that to the City of Birmingham’s roughly 1500 people per square mile.)

We intuitively know that below certain levels of density, it’s hard to have adequate transit systems, walk-able streets, successful commercial areas, adequate greenways and natural areas, wise conservation of resources, etc. A fascinating article written by Lloyd Alter over on treehugger attempts to objectively analyze urban density, and arrives at some interesting conclusions.

So is NYC the best we have?

One of the article’s illustrations is the above map (courtesy UNEP) that shows urban density along the horizonal axis, and transport costs along the vertical. Note that transport costs include private and public transportation. At first glance this graph shows that New York City has the highest US density of major cities, and the lowest transport costs–validating the theory that the denser you get, the cheaper the transportation costs. But looking closer, you notice that Los Angeles, while having higher transport costs (all that freeway driving and limited public transit) has a HIGHER density as a city than New York (which includes very-dense Manhattan but also less dense boroughs). Also, much less dense Australian cities like Perth or Sydney have considerably lower transport costs than New York. So, at least in the middle of the graph, density and transport costs don’t necessarily correlate. And neither do our assumptions about the sprawl of LA vs. the tidy density of NYC.

Maybe this is it

Alter decides after examining the evidence that Greenwich Village (above) or central Paris–with their low-to-medium height buildings and small blocks–represent the ideal densities which support good transit, street life, and a sense of community without tipping over into the need for hugely expensive (and energy-intensive) mega-towers, vast parking garages, etc. Paris was largely rebuilt in its current form by imperial fiat; Greenwich Village is a 19th-century layering of former tenements and townhouses. Neither is necessarily possible to “replicate” today. But the issues surrounding urban density in these models and elsewhere are worth pondering as we decide how the Birmingham of the future will look.

[thanks to ncindc for the U Street pic; UNEP for the graph;  frankeggen for the Greenwich Village pic]

14 responses to “Questioning density

  1. God, I was working at the Source Theatre on 14th when they were building those buildings. It made getting around the area into a monumental disaster.

  2. Never tried it, by that point I was in the city less and College Park, MD more.

  3. I hope something like this level of density will be specified for certain infill zones under the new City of Birmingham comprehensive plan. Four stories seems falls under a lower construction cost formula, too. The lead architecture critic for Nashville thinks they should push this scale rather than the towers they’ve seen.

  4. Graphing transport cost per capita handicaps the visible effect of density, but underlines the significance of the correlation.

  5. Moderation is a good thing, right?
    Greenwich village is likely the same density now as it has traditionally been for over 100 years, excepting the overcrowding of the late 19th century where multiple families shared the same apartments. That overcrowding is largely the reason for the adoption of horizontal zoning based on post-World War One European urban planning theories.
    The urban environment is a form of an ecosystem, albeit man-made, and like all ecosystems, balance is necessary to maintain the efficacy of that system. Over-correcting is a common frailty of human nature when solving complex problems.

  6. I would like to see a comparison between LA’s Hollywood/West Side and Manhattan. While I have never been to New York, I have been to LA many times and Hollywood/Westside is very dense and yet most people still get around with cars. (BTW, trying to find a place to park is a nightmare). From my understanding the majority of people living in Manhattan do not own cars. Also, Asian cities such as Hong Kong have no choice in their built environment. Their vast populations and lack of land force them into the skyscrapper/highrise model.

    • My guess would be Hollywood/Westside would be a good bit less dense than Manhattan. However, it would probably be more dense than New York City as a whole. Not knowing LA that well, this is still stunning to me–the vision of LA with all those single-family homes with lawns and cars wouldn’t seem to compare to even the remote parts of Queens in terms of density. But it clearly does. And you are right that most people in Manhattan do not own cars, similar to Hong Kong; and both places are forced to build upward due to the high cost of land and population pressure. Thanks for reading.

      • There are really two LA’s. There is the city of LA and then there is suburbia. The city is very dense. What I think Alter fails to connect is that density forces cities into more efficient transit use. I really don’t think the city of LA can become any more dense with a car based transit system. (This is being demostrated by their desperate desire to build light rail.) Shanghai is a great example. 20 years ago Shanghai had no subway system. In order for the city to grow it had to build a subway system. I do like his article though and agree that the ‘Goldilocks’ model is best.

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