This week some US Census results were published and as ever people are surprised that the densest city areas are not New York and East Coast cities but Los Angeles and San Francisco.
The highest-density urban areas with populations greater than 1 million included, in order:
1. Los Angeles (6,999 per square mile)
2. San Francisco (6,266)
3. San Jose (5.820)
4. New York (5,319)
5. Las Vegas (4,525)
But surely LA is car orientated sprawl!, but in another interesting fact the setreo type of dreadful public transport use is false, as Freakenomics points out.
compared with the majority of U.S. cities, Los Angeles is not a transit wasteland. The region is second in the nation in transit patronage, behind only New York. Even on a market share basis (passenger transit miles traveled as a share of all miles traveled), Los Angeles’s ridership rate is relatively high: 11th among the 50 largest urban areas.
Also Las Angeles has the lowest commute to work times of of mega metropolitan area in the world. Whys is that? You might hypothesise as I first did that its sheer volume of freeways was such given that it blew past the point at which building roads induces traffic because there were no longer potential induced households to switch. I was wrong again Freakenomics:
taking into account the area’s vast size, the network is one of the most underdeveloped in the U.S. According to the Federal Highway Administration, of the 36 largest metro areas, Los Angeles ranks dead last in terms of freeway lane miles per resident. (Chicago is second to last, and New York is near the bottom as well. The most freeway-heavy big city by this measure is Kansas City.)
So clearly LA is a very different beast to the likes of Houston, Kansas City or Pheonix of low density, high highway sprawl but what?
Eric Eidlin in an Excellent Article ‘What Density Doesn’t Tell us about Sprawl’ in Access #37 puts his finger on it. I would recommend reading the whole article but here are some highlights.
These facts present a bit of a mystery. If one were to measure sprawl by measuring a region’s average level of Vehicle Miles Traveled (VMT), Los Angeles would certainly qualify as sprawling. But if we measure sprawl by population density, LA would not sprawl at all. In fact, it would be the least sprawling urbanized area in the country. How can Los Angeles be so dense and yet also exhibit so many characteristics associated with sprawl, including high levels of car travel (both in per capita and absolute terms) and low rates of walking, bicycling and transit ridership?
Part of the answer lies in the vagaries of Census geography. Sprawl is a regional attribute, so when observers point out that LA is denser than New York, they are not talking about the cities of Los Angeles and New York. Rather they are talking about the urbanized area, which is essentially the combined area of the cities and their suburbs. The other part of the answer is that density by itself—the simple ratio of population to square mile—is not a very useful way to measure sprawl. What matters is the distribution of density, or how evenly or unevenly an area’s population is spread out across its geographic area. If we look at the density distribution in Los Angeles, we notice that its suburbs are much denser than those of other large U.S. cities, such as New York, San Francisco or Chicago. These high-density suburbs compensate for the comparatively low density of LA’s urban core, and, in so doing, increase the average density of the area as a whole. In other words, Los Angeles has both a relatively high density and a relatively even distribution of density throughout its urbanized area.
The LA region’s combination of high, evenly distributed density puts it in an unfortunate position: it suffers from many of the problems that accompany high population density, including extreme traffic congestion and poor air quality; but lacks many of the benefits that typically accompany more traditional versions of dense urban areas, including fast and effective public transit and a core with vibrant street life. Los Angeles has, to borrow a term coined by urbanist William Fulton, “dense sprawl.” (Or, to be less charitable, it has “dysfunctional density.”) It is too dense to function like classic suburbia, but also has few areas dense enough to be a “city” in the manner of central city New York or San Francisco…
Los Angeles lacks a super-dense core like Manhattan. But it also lacks a very low-density suburban periphery. Suburban neighborhoods in the Los Angeles region are much denser than their counterparts in the Northeast and Midwest. Indeed, one might say that they are not classically suburban, in the sense that few of them offer large houses on large plots of land, uncongested roads, and easy access to open space.
Why do standard measures of density mislead? Two reasons: first, the standard measure relies too much on where the urbanized area’s formal boundary is drawn, and second, the measure is determined by total land area, even if some of the land is sparsely populated….So is there a better way to measure density? Below I discuss three alternative approaches that might be more helpful in understanding the development patterns of dispersed and polycentric urban regions like LA. One method measures unequal density in the distribution of population; the other two attempt to measure density as it is experienced by the average resident of a given urban area….
One approach is to measure the extent to which the population density varies across an urban area. Using a statistical tool called the Gini coefficient, we can get a sense of the degree of variation for different urban areas. The Gini coefficient is based on the Lorenz curve, a cumulative frequency curve that compares the distribution of a specific variable (in this case, population density) with a uniform distribution that represents perfect equality….
Another approach to measuring density, which was developed separately by both Gary Barnes and Chris Bradford, is to use “perceived” or “weighted” density. The purpose of perceived density is to capture the density of the place in which the average person lives. A good way of conceptualizing the difference between “standard density” and “perceived density” is that where standard density measures the average amount of land around each resident of a city, perceived density measures the average number of people around each resident of that city. Measuring perceived density involves four steps: 1. Divide the city into small geographic units such as census tracts. 2. Calculate the standard density of each of these census tracts. 3. Assign a weight to each census tract that is equal to its share of the total population of the city. 4. Average the weighted densities of all of the city’s census tracts. This produces a weighted or “perceived” density for the city….
Bradford pushed the concept of perceived density a step further by developing the density gradient index. The density gradient index, which is the ratio of perceived density to standard density, is an indication of the unevenness of population distribution—or, to use Bradford’s terminology—a measure of “clumpiness.”
Many urbanists admire places like Boston, New York and San Francisco, which give their residents a wide range of transportation options and have charming multimodal streets. Many urbanists admire Los Angeles as well, of course, but recognize that it is often a difficult place to walk, bike or use public transportation. However, planners who seek to emulate Boston or New York, or to avoid the less desirable elements of LA, will go astray if they simply focus on increasing density. The urban form of older metropolitan areas is one of great variance, not great density. The New York urbanized area offers its residents both a super-dense, vibrant core and a low-density suburbia. The places where land is used very intensively in the center often see it used much less intensively on the outskirts. While it is possible to have an area that contains nothing but extraordinarily high density, such places are unusual, and often islands (think Hong Kong or Singapore).
Acknowledging these land use patterns should make us question some conventional planning goals. We might say we want more density or less sprawl. We might even say that we simply want more places to look like San Francisco or New York. But what exactly are we trying to accomplish by doing this? Do we want super-dense urban centers, or very-low density suburbs, or both? These aren’t easy questions to answer, and standard measures of density will offer us little help in trying to answer them.
It is also important to realize that no measure of density, no matter how comprehensive, can capture every dimension of sprawl. Much of what we consider sprawl is determined less by the density of people or jobs, and more by how buildings and parking are arranged on the street, and whether streets are designed in a way that makes walking and biking safe and comfortable. Nevertheless, in the future planners and policymakers might find it useful to assess the perceived density of the places they are trying to improve. Policymaking is about people, after all, so perhaps we are better off examining density as people experience it.
Or as I would put it – how would you increase the perceived density in a neighbourhood in a way which does not increase car use? This has block level urban design and strategic implications for smart growth. Thought for the day.
Footnote: The term perceived density sounds subjective – I prefer propinquity index
Further Reading
Gary Barnes. 2001. “Population and Employment Density and Travel Behavior in Large U.S. Cities.”
Minnesota Department of Transportation, September.
Chris Bradford. 2008. “Density Calculations for U.S. Urbanized Areas, Weighted By Census Tract.
Austin Contrarion blog post. March 24.Available: http://austinzoning.typepad.com/austincontrarian/2008/03/weighted-densit.html.
Eric Eidlin. 2005. “The Worst of All Worlds: LosAngeles and the Emerging Reality of Dense Sprawl,” Journal of the Transportation Research Board, No. 1902, pp. 1–9.
Paul Sorenson. 2009. “Moving Los Angeles,” Access, Vol. 35, Fall, pp. 16–24.
Peter Newman and Jeffrey Kenworthy. 1999. Sustainability and Cities: Overcoming Automobile Dependence. Washington, DC: Island Press
The Regional City: Planning for the End of Sprawl Peter Calthorpe, William B. Fulton Island Press 2000
Decisions, Decisions, Decisions 