Are airports becoming the ‘new downtowns’ of American cities? In new research which examines 62 airports in 51 US metropolitan areas, Stephen Appold finds that airports are important, with a large majority anchoring their own concentrations of employment, but that this employment varies compared to that of city CBDs. He writes that understanding how much employment, of what types, and for what reason locate near airports will aid in allocating land as cities continue to change

Appold, Stephen

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blogs.lse.ac.ukhttp://blogs.lse.ac.uk/usappblog/2015/08/31/airports-are-playing-an-important-role-in-the-remaking-of-us-cities/Airports are playing an important role in the remaking of UScities.Are airports becoming the ‘new downtowns’ of American cities? In new research which examines62 airports in 51 US metropolitan areas, Stephen Appold finds that airports are important, with alarge majority anchoring their own concentrations of employment, but that this employment variescompared to that of city CBDs. He writes that understanding how much employment, of whattypes, and for what reason locate near airports will aid in allocating land as cities continue tochange.What is the spatial form U.S. cities in the early 21st-century?  (The terms, “urban,” “metropolitan,”“city,” and “region” are used interchangeably here.)  Despite the importance of the question for informing theory,planning and real estate development, we may have a better overview of ancient and medieval city structure thanwe do of our own, sometimes characterizing it simply as endless sprawl.  Yet, as we approach the closing of thecrabgrass frontier, understanding the cities we have created is a critical input into creating the cities we need.Not all cities have the same structure but, in various combinations and strengths, several of the basic spatialbuilding blocks are common: a center surrounded by a cone of decreasing density of activity, corridors alongmajor primary access routes, clusters of employment in addition to the CBD, and, perhaps, clusters ofemployment near the airport.  Figure 1 provides an overview of the spatial structure of one U.S. city, Charlotte,North Carolina which spills over municipal boundaries to reach over several counties and crosses a state line aswell as a river.  Employment is more concentrated than the at-home population.  The CBD is clearly discernableat the intersection of the five primary radial routes.  In addition, clusters of employment can also be seen.Figure 1 – Charlotte Region Employment and Population DensityThe Airport City ThesisA handful of transportation innovations over the last century, electric street cars, automobiles, and airplanes, havehad profound impacts on the size, distribution, and internal structure of cities with several authors positing an air-auto age.  The infrastructure supporting these transportation modes are not intrusions upon cities but fundamentalcomponents of large contemporary cities.  Nodes of transport interchange, whether central points of convergenceor places of transfer between long distance and local means of transport, frequently serve as anchors for urbandevelopment.  Consequently, many cities have their origins at sea harbors (New York), river junctions (Pittsburgh)or crossings (St. Louis), rail depots (Atlanta), and perhaps even highway interchanges (Tysons Corner).  Theacknowledged salience of such nodes in shaping cities might be best evidenced in transit-oriented and railwaystation development.Airports have been said to anchor a specifically late 20 th century- early 21st century urban form: airport cities(defined here as concentrations of employment on and near airports).  Some have argued that, in a major re-arrangement of space, airports are becoming “the new downtowns” with terminals forming the central square (seeFigure 2) of “new cities” functionally splitting away from and overtaking the “old cities” from which they hademerged.Figure 2  – Airports as “Central Squares”Prevalence and ImportanceMy recent examination of the 51 U.S. metropolitan areas with populations of one million or more in 2000 and the62 airports with scheduled passenger service serving those cities reveals that airports are important. Airport citiesnot only exist, they are prevalent: 80 percent of the commercial airports included in the analysis anchor sufficientemployment to constitute an employment agglomeration (using one common operationalization).Figure 3 shows that airport cities are significant, but not dominant, urban centers.  (Airport-CBD corridors arecontinuous agglomerations of employment including both an airport and the CBD centroid, such as in Charlotte.) Airport area employment averaged one-third to one-half that of CBDs, depending upon operationalization.  Airportcities collectively accounted for a smaller proportion of metropolitan area employment than the combined non-CBD employment subcenters but were often individually larger.Figure 3 – Percent of Urban Employment by Selected Spatial Building BlockTo put the impact of these building blocks of the distribution of metropolitan employment into context, Figure 4summarizes the average percent of metropolitan employment within the specified distances of selected anchors. Airports anchor approximately the same proportion of metropolitan employment as selected large non-CBDsubcenters.  The relatively few major radial highways, as seen in Figure 1  above, anchor a significantly higherproportion of employment in corridors.  Of course, past a point, CBDs, airports, and the centers of non-CBDsubcenters tap into the overall urban activity cone.  A varying, but large, proportion of employment is outsideidentifiable clusters.Figure 4 – Percent of Metropolitan Employment near Key Employment AnchorsThe relative employment in airport areas, compared to the CBDs, varied: the location of the airport with respect tomajor highways and distance from the CBD but not air-intensity, had large impacts on the relative size of theairport city.  Figure 5 charts the relationship of airport city size to distance from the CBD.  The timing of urbanexpansion may have an impact on the size of the employment agglomeration near airports.  Residences oftenspread from the center city before employment did, pre-empting commercial development.Figure 5 – Percent of Metropolitan Employment within One Mile of the Principal Airport and Distance ofthe Airport from the CBDAirport Cities as Employment SuburbanizationFigure 6 summarizes the general specialty sectors of CBDs, airport areas, CBD-airport corridors, and non-CBDsubcenters.  Scores above 1 indicate specialization in that sector.  Airport areas specialize first and foremost intransportation, wholesale trade, and to a lesser extent, manufacturing.  Beyond that, their sectoral specializationsresemble those of non-CBD subcenters.  Given the disamenity, airport areas might be attractive for sectors whichare not sensitive to noise, such as manufacturing and wholesaling, but require access to urban markets,highways, and labor pools even when they have little connection to aviation.   The hedonic pricing literature findsthat airports exert both a positive access effect and a much stronger noise effect on residential homes.  Althoughno systematic research has been found, the relative strength of the impacts are likely reversed for commercial realestate, even if there is no strong need for airport access.Figure 6 – Sector Employment Location Quotients by Type of Urban ElementCentral cities have retained their spatial dominance to a surprising degree.  Employment in sectors which relyheavily on air transportation remains concentrated in CBDs.  Public administration, finance, information, andprofessional services are more over-represented in CBDs than elsewhere.  Airport cities are essentially suburbanemployment subcenters with an airport.Residential Location and Airport City SizeThe above summarizes the overall tendency but, as Figure 5 suggests, there is wide variation in airport city sizeand character.  High-status residential areas are one factor which may help pull (air transportation-using)producer service employment in their direction and push manufacturing and distribution away.  Figure 7 andFigure 8 map the contrasting Atlanta and Dallas-Fort Worth (DFW) regions, respectively.  In these maps, blueindicates that population exceeds employment and red the opposite.  The deeper the blue, the higher the averagehousehold income is; the deeper the red, the higher the density of employment.  In Atlanta, many of the highdensity employment areas are to the north of the CBD.  The same holds in Dallas-Fort Worth but in that case, theairports are also and the corridor of high density employment stretches from central Dallas northwest past Lovefield, to, and perhaps beyond, DFW.  The statistical results of the analyses testing for the impact of suchresidential districts are suggestive, but not conclusive.Figure 7 – Employment Density (red) and Household Income (blue) in Atlanta, 2000Figure 8 – Employment Density (red) and Household Income (blue) in Dallas-Fort Worth, 2000 Implications for planningDiscussions surrounding the proposed Thames Estuary Airport in London, Chicago’s O’Hare modernizationproject, and the redevelopment of LaGuardia airport in New York underscore the importance of airport areaplanning.  Understanding how much employment, of what types, and for what reason locate near airports will aidin allocating land among uses, hopefully with the effect of maximizing safety, minimizing noise disamenity, andmore efficiently using increasingly scarce urban land as denser development spills over into what have beentermed urban grey areas.It should be emphasized that the volume of employment surrounding an airport is not a measure of its value to acity.  Rather airports are one component of a system of air transportation which can help reduce the costs of tradeand thereby catalyze outwardly-looking urban economic activity.  Over the course of the second half of the 20thcentury, the U.S. economy became almost three times more passenger air-intensive than it was in the 1950s,reaching approximately 60 revenue-passenger-miles per $1,000 of GDP.  The growth in air travel may haveslowed in the U.S. as the market approaches saturation but there is an accelerating need to better integrateairports into urban design as cities remake themselves for new uses.This article is based on the paper ‘Airport cities and metropolitan labor markets: an extension and response toCidell’, in the Journal of Economic Geography.Featured image credit: Supplied by author.Please read our comments policy before commenting.           Note:  This article gives the views of the author, and not the position of USAPP – American Politics and Policy, norof the London School of Economics.Shortened URL for this post: http://bit.ly/1NIEdr7 _________________________________ About the authorStephen Appold – The University of North Carolina, Chapel HillStephen Appold is at the Kenan Institute of Private Enterprise, Kenan-Flagler Business School, atthe University of North Carolina, Chapel Hill. His research interests include airport cities and thespatial structure of contemporary cities.CC BY-NC 3.0 2015 LSE USAPP

Airports are playing an important role in the remaking of UScities

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