Expert Commentary

Retail parking lots, environmental impacts and development policies: Research roundup

2012 roundup of recent academic studies on the economic and environmental impact of parking lots, impervious surfaces and other automobile-related infrastructure.


A parking place is a simple thing, conceptually speaking: a spot to keep the car when it’s not in use. But multiply that by the hundreds of millions of Americans who choose to use a car for transportation (or who live in an area where they have no choice but to use a car) and the question becomes far more complex and its impacts significantly greater. During holiday season, parking lots are brimming at malls across America, but the rest of the year they’re often vacant, raising the issue of whether there may be better uses.

The smart growth movement has helped communities rethink development, yet year after year developers continue to “improve” large swaths of land by constructing buildings or paving them over. But the benefits for cities of constructing large amounts of surface parking are open to question. For example, between 1960 and 2009 Hartford, Connecticut, quadrupled the number of downtown parking places in an attempt to compete with suburban office parks, yet during that time its center lost more than 60% of its residents and thousands of jobs.

For many municipalities large and small, parking consumes not only the time of governing bodies and planning boards, but also scarce financial resources. As the number and size of parking lots and other impervious cover has increased, so have their environmental, health and social impacts. In some states policymakers are pushing back — in New Jersey, a chunk of the northern part of the state has been rezoned by the legislature to limit the amount of impervious cover and preserve aquifers.

The following are studies and reports that can help foster deeper understanding of municipal planning and water quality issues, as well as wider debates about development and promoting commerce.



“The Environmental and Economic Costs of Sprawling Parking Lots in the United States”
Davis, Amelie Y. Land Use Policy, Vol. 27, Issue 2, April 2010, 255-261.

Abstract: “Urban sprawl is considered by most environmental scientists and urban planners to be a serious environmental problem. However, public perception about parking availability often forces planning offices to recommend parking lot sizes that exceed daily demands. The recent trend of increasing the size of stores, churches and even schools comes with increasing the size of parking lots that service these buildings. The objective of this paper is to analyze space allocation of parking lots in a typical Midwestern county and to estimate the supply of parking spaces to potential demand. We also estimate the loss of ecosystem services represented by the area of parking lots in this county. We found that parking lots cover 5.65 km2 (1,397 acres) of Tippecanoe County, Indiana which implies that 0.44% of the county area is devoted to parking lots. Our results show that there are approximately 2.2 parking spaces per registered vehicle, that parking lots make up more than 6.57% of the total urban footprint in this county, that the area of parking lots exceeded the area of parks in the city limits by a factor of three and that parking lot runoff and pollutants are significant compared to runoff and pollutants from these areas prior to their conversion to parking lots. As other authors have done before us we lament the poor use of land in urban regions of the United States, and encourage planners to think creatively about the use of land for parking.”


“Parking Infrastructure and the Environment”
Chester, Mikhail, et al. Access: The Magazine of the University of California Transportation Center, fall 2011.

Excerpt: “Estimating the monetized health and environmental costs of parking infrastructure represents an important step in developing total transportation cost assessments to inform policy decisions. We evaluate these costs using an approach developed by the National Research Council’s “Hidden Costs of Energy” study. This allows an assessment of the total impact of parking construction and maintenance by assigning damage costs to each pollutant. We can then evaluate the effects of parking in typical high-impact urban and low-impact rural counties. Using these estimates, LCA enables us to attach dollar amounts to the external costs of parking infrastructure…. The parking infrastructure estimated in Scenarios A through C costs the U.S. between $4 and $20 billion per year. Per space, this amounts to between $6 and $23 per year. The low end of this range represents a parking space constructed in a low-density rural area, whereas the high end typifies a space in a high-density urban environment. Everyone bears this cost in the form of adverse health impacts, building damage, and reduced agricultural production, to name a few.”


“The Uneasy Case for Lower Parking Standards”
Bowman, Cutter, W.; et al. FEUNL working paper series No. 564, 2012.

Abstract: “Minimum parking requirements are the norm for urban and suburban development in the United States (Davidson and Dolnick (2002)). The justification for parking space requirements is that overflow parking will occupy nearby street or off-street parking. Shoup (1999) and Willson (1995) provide cases where there is reason to believe that parking space requirements have forced parcel developers to place more parking than they would in the absence of parking requirements. If the effect of parking minimums is to significantly increase the land area devoted to parking, then the increase in impervious surfaces would likely cause water quality degradation, increased flooding, and decreased groundwater recharge. However, to our knowledge the existing literature does not test the effect of parking minimums on the amount of lot space devoted to parking beyond a few case studies. This paper tests the hypothesis that parking space requirements cause an oversupply of parking by examining the implicit marginal value of land allocated to parking spaces. This is an indirect test of the effects of parking requirements that is similar to Glaeser and Gyourko (2003). A simple theoretical model shows that the marginal value of additional parking to the sale price should be equal to the cost of land plus the cost of parking construction. We estimate the marginal values of parking and lot area with spatial methods using a large data set from the Los Angeles area non-residential property sales and find that for most of the property types the marginal value of parking is significantly below that of the parcel area. This evidence supports the contention that minimum parking requirements significantly increase the amount of parcel area devoted to parking.”


“Watersheds at Risk to Increased Impervious Surface Cover in the Conterminous United States”
Theobald, D.; Goetz, S.; Norman, J.; and Jantz, P. Journal of Hydrologic Engineering, 2009, 362-368.

Abstract: “We estimated impervious surface from United States census housing density data sets for the conterminous United States to examine the distribution and extent of impaired watersheds, and to estimate the risk to watersheds from development in the near future. We used regression tree methods to relate estimates of current housing density to the 2001 National Land Cover Database (NLCD) percent urban imperviousness. As of 2000, we estimate 83,749 km2 of impervious surface (IS) cover across the United States (about 9.6% lower than the NLCD). We estimate that IS cover will expand to 114,070 km2 by 2030. About 7% of eight-digit Hydrologic Unit Code (HUC) watersheds (3.6% of the conterminous United States) were stressed or degraded ( >5% IS) in 2000, and we estimated that this will increase to nearly double to 8.5% of watersheds by 2030 (6.3% of area). We explored the subtle differences of fine-grain pattern for different urban land use types by comparing our national estimates of IS to those developed for the Chesapeake Bay watershed. We also found important nonlinear affects of watershed scale and aggregation, whereby estimates of IS could differ by roughly ten-fold.”


“Parking, People and Cities”
Manville, M. and Shoup, D. Journal of Urban Planning and Development, 2005,Vol. 131, 233-245.

Abstract: “In this study of how off-street parking requirements affect urban form, we begin by analyzing the relationship between population density and streets in cities. We find that denser cities devote a greater share of their land to streets, but also have less street space per person. This relationship results in part from the difficulty of constructing new streets in built-out areas. The amount of street space does not increase as fast as population density, and this in turn helps explain why dense areas have less vehicle travel per person but higher levels of congestion. In contrast to streets, new off-street parking is supplied continually, owing largely to minimum parking requirements that make new development contingent on the provision of parking spaces. But the ample supply of off-street parking makes traffic congestion worse and inhibits street life. We recommend either removing off-street parking requirements, or converting them from minimums to maximums.”


“U.S. Constructed Area Approaches the Size of Ohio” (PDF)
Elvridge, Christopher. EOS, Transactions, American Geophysical Union, Vol. 85, No. 24, 2004.

Abstract: “The construction and maintenance of impervious surfaces—buildings, roads, parking lots, roofs, etc.—constitute a major human alteration of the land surface, changing the local hydrology, climate, and carbon cycling. Three types of national coverage data were used to model the spatial distribution and density of the impervious surface area (ISA) for the conterminous United States. The results (Figure 1) indicate that total ISA of the 48 states and Washington, D.C. is 112,610 km2 (±12,725 km2), which is slightly smaller than the state of Ohio (116,534 km2) and slightly larger than the area of herbaceous wetlands (98,460 km2) of the conterminous United States.”


“Smart Growth: Why We Discuss It More than We Do It”
Downs, Anthony. Journal of the American Planning Association, 2005, Vol. 71, Issue 4.

Abstract: “The Smart Growth vision has a strong intellectual and emotional appeal, compared to more sprawl. However, though some places follow Smart Growth policies, they are outnumbered by those where such policies are commonly discussed but rarely practiced effectively. Why is this the case? Successful implementation requires adopting policies that give up long-established traditions, including local home rule and low-density living patterns. These intermediate steps are unappealing to most Americans. This article analyzes where Smart Growth advocates among urban planners, government officials, environmentalists, and real estate developers should focus their attention if they hope to move from vision to reality.”


“Where Is the Café? The Challenge of Making Retail Uses Viable in Mixed-use Suburban Developments”
Grant, Jill. Urban Studies, January 2011, Vol. 48, No. 1, 177-195.

Abstract: “Contemporary planners see mixing residential, retail and other compatible uses as an essential planning principle. This paper explores the challenges that planners, developers and municipal councilors encounter in trying to implement retail uses as part of the mix in suburban areas in three Canadian cities. The study finds that planners employ evolutionary theories of urban development to naturalize their normative visions of walkable and sociable communities. By contrast, developers point to consumer behavior to explain why planners’ ideas on mix do not work. In a society where people shop at big-box outlets, making the local café or pub commercially viable proves increasingly challenging.”


“Impervious Surfaces and Water Quality: A Review of Current Literature and Its Implications for Watershed Planning”
Brabec, Elizabeth, et al. Journal of Planning Literature, 2002, Vol. 16, No. 4.

Abstract: “Impervious surfaces have for many years been recognized as an indicator of the intensity of the urban environment and, with the advent of urban sprawl, they have become a key issue in habitat health. Although a considerable amount of research has been done to define impervious thresholds for water quality degradation, there are a number of flaws in the assumptions and methodologies used. Given refinement of the methodology, accurate and usable parameters for preventative watershed planning can be developed, which include impervious surface thresholds and a balance between pervious and impervious surfaces within a watershed.”


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