July 7, 2015 Eric Bethany

Read: Richard Willson, “Case against Minimum Parking Requirements”

In a recent post, we referenced Richard Willson’s book Parking Reform Made Easy, specifically the second chapter, “Case against Minimum Parking Requirements.” We have yet to find a more complete summary of the detrimental effects of legally-mandated parking, an issue that we and many other architects and planners believe is central to the pursuit of creating more enjoyable and sustainable urban environments. Willson and Island Press were kind enough to grant us permission to share this chapter, in the hopes that access to these ideas might increase understanding of how parking requirements undermine nearly every positive aspect of urban space. We encourage you to read Willson’s book in its entirety; it can be found at http://www.islandpress.org/parking-reform-made-easy.

From Parking Reform Made Easy by Richard W. Willson: Case against Minimum Parking Requirements (pages 23-33):

The following summarizes the case against conventional parking requirements, presented in terms of transportation, density and design, economic development, sustainability, and city administration. Conventional parking requirements encourage private vehicle use, adversely impact alternative travel modes, ignore cost effectiveness, reduce density, create inhospitable project design, thwart development and economic activity, hamper affordable housing production, hamper infill and adaptive reuse, cause direct environmental impacts, cause indirect environmental impacts, disadvantage nondrivers, lower physical activity, and imprecisely represent actual parking utilization. Each is described in the paragraphs that follow.

Encourage private vehicle use and lengthen trips

Parking requirements compel developers to invest in automobile access, often as the only mode of site access improvement required. By forcing the use of so much land for vehicle storage, parking requirements indirectly shield drivers from the cost of parking while at the same time providing them with a high level of convenience. This encourages driving over other travel modes. Shoup (2005) calls parking requirements “a fertility drug for cars.” The parking supply and associated road system demonstrate a clear priority for moving and storing private vehicles, favoring them over other modes. The one-dimensional nature of that type of access system is evident in the journey-to-work travel mode for residents of the city of Ontario, California (shown in fig. 1.1). In that suburban community, 91.6 percent of work trips are in private vehicles as a driver or passenger (U.S. Census Bureau 2012a). Ironically, parking requirements intended to reduce congestion on streets around a development have the effect of lowering achievable density because a given level of population and employment will spread out and use more land on a regional basis. This sprawled arrangement increases regional vehicle miles traveled per capita because places are farther apart.

Adversely impact transit and alternative modes

Research tells us that travelers consider comparative travel time and costs as well as convenience and safety in selecting travel modes. Minimum parking requirements make parking charges unlikely because they interfere in the supply and demand interaction that would yield a market parking price. The lack of paid parking furthers the economic advantage of driving and parking. Why pay a transit fare if you can park free? Why consider arranging your household with one less vehicle if two spaces are bundled with your apartment rent? Parking requirements also affect site design and the feasibility of using modes other than the private vehicle. When buildings are set back from the street behind the parking, serving these sites with transit is difficult because buses cannot get close to the front doors. When density is lower, transit service is less economic, and when transit is less economic, service frequencies are low. This makes transit less competitive. These site design issues also lower the likelihood of walking or bicycling to the site. Finally, parking requirements enable a high level of private vehicle use, which results in wide roads that create an unpleasant or unsafe environment for pedestrians and bicyclists. The roads shown in figure 1.1 meet conventional engineering standards, but their width discourages other forms of transportation— East 4th Street and North Milliken Avenue are 145 and 165 feet from curb to curb, respectively. East 4th Street has a speed limit of 55 miles per hour, creating an environment that is unfavorable or impossible for buses, neighborhood electric vehicles, bicycles, and pedestrians.

Ignore cost effectiveness

Parking requirements ignore the cost effectiveness of parking as compared with alternative travel modes. Requiring parking imposes costs related to land, construction, and parking operations and maintenance (O& M). Rarely is the cost effectiveness of parking compared to other feasible travel modes. While actual parking costs vary from place to place and site to site, the following provides an order of magnitude of those costs, combining amortized capital costs with O& M costs:1

  • Suburban surface parking: $ 2.42 per space per day ($ 200,000 per acre land, $ 5,000 per space capital cost, $ 200 per space per year O& M).
  • Urban three-story parking structure: $ 7.44 per space per day ($ 500,000 per acre land, $ 23,800 per stall capital cost, $ 300 per space per year O& M).
  • CBD (central business district) underground structure: $ 11.16 per day ($ 0 land cost, $ 40,000 per space capital cost, $ 500 per space per year O& M).

Parking requirements ignore that these costs may be higher than the per-unit costs of alternative transportation modes, such as providing bicycle parking, pedestrian facilities, or ongoing subsidies to transit. For the urban three-story parking structure example, the developer/ owner could offer a $ 7 per day incentive for using transit, walking, or bicycling for every parking space reduced. If parking requirements require the overbuilding of parking, then the cost per space used is even higher. If, for example, a development is required to build twice as much parking as is actually used, then the cost per parking space used is doubled.

Reduce density

Although zoning code provisions such as setbacks, height limits, and floor area ratios directly affect development density, parking requirements have a surprisingly strong influence on density. At about 325 square feet of area per parking space, including drive aisles, parking consumes large amounts of site or building area devoted to a single, low-intensity use. The primary impact is determining the amount of land available for the building footprint after the parking requirement is fulfilled. In some settings, land required for parking may act as more of a limitation to project density than building height, floor area ratio, or setback requirements. In urban areas, the high cost of parking structures reduces building size if it is not economic to build the amount of required parking; the resulting high cost of development thwarts infill development and therefore limits core area density. The phenomenon of excess parking supply limiting density is shown in the case of Ontario Mills Mall shown in chapter 1, figure 1.1, where the parking is sized for peak shopping days in November/ December, not a typical weekday or weekend day.

Create inhospitable project design

Projects shaped by parking requirements often place parking at the front of the facility with the building set back from the street. This is intended to increase the desirability of the building by making the parking supply highly visible, but the practice makes the street inhospitable and makes bus, walking, or bicycle access more difficult. Figure 2.1 shows the view a pedestrian sees of Citizen’s Bank Arena. Designers of this project were attentive to the patron’s experience once within the arena but require those arriving on foot or by transit to traverse a long distance to reach the facility. Even those who drive must walk through a large parking lot. The impact of lower site density and locating the project in the middle of surface parking lots makes shared parking more difficult— walking distances are long and connection between sites is difficult. In fact, the Citizen’s Bank Arena and the Ontario Mills Mall are perfect candidates for shared parking but they are so far apart that the feasibility of sharing is limited. Referring again to figure 1.1, walking from the multifamily residential development to Ontario Mills takes fifteen minutes at a moderate walking pace, including crossing two very wide arterial streets. Would not residents of that development be tempted to drive to the mall and thereby increase its parking utilization?

Thwart development and economic activity

While parking may add to the overall value of a development project, it is usually dead weight on the development pro forma. As shown previously, parking adds land, construction, and operating costs but provides little or no direct revenue. To be fair, if tenants or owners are willing to pay higher rents or prices for projects that have lots of parking, there is an economic value. But often, parking requirements are higher than what developers would build in gauging the market and the financial feasibility of development. The cost associated with fulfilling parking requirements may cause the return on investment to be too low for the development to proceed, thereby thwarting otherwise desired investment and economic development.


 Figure 2.1. The pedestrian experience in parking-first environments

A commercial parking requirement of four spaces per 1,000 square feet requires 1,300– 1,400 square feet of parking area for every 1,000 square feet of building area. Obviously, both the building and the parking can be in multistory structures, but that is only feasible when the combination of land costs, construction costs, and rents pencil out. When land prices dictate that parking will be provided at grade, parking requirements affect the amount of site required for a given-sized building or limit the size of a building given a fixed-sized site. These costs affect return on investment directly through project costs, and indirectly through achievable density and therefore projected revenue. The general result of parking requirements and their associated costs is an urban form that is more parking lot than building, and a low economic productivity of the land. In addition, excessive parking requirements lower land value since less rent-generating uses can be built. Lower density, lower value developments produce less property, retail sales, and hotel tax revenues, and fewer business license fees.

Make the construction of affordable housing more challenging

Parking requirements increase the development cost of housing. They also increase the land cost per unit by lowering achievable density. Both impacts make housing less affordable. In larger, high-end housing units, parking is a small proportion of total square footage and building cost, but it has a greater relative impact on affordable housing (Jai and Wachs 1998; Litman 2011; Manville and Shoup 2010). In addition, parking requirements may prevent households from choosing lower cost units that do not have parking. By hampering the production of affordable housing and increasing rents, parking requirements act as an indirect form of exclusionary zoning. This issue is explored further in chapter 6.

Hamper investment in infill development and adaptive reuse in core areas

Parking requirements reduce investment in built-up areas, small sites, brownfields, and sites that have awkward lot configurations. In the first case, land for parking is not available in many built-up areas. Furthermore, an efficient lot layout cannot be achieved on small or irregularly shaped sites, so more land area per parking space is needed. These sites may be in places where investment, rehabilitation, and small business formation are most needed. This is illustrated when a business startup wants to reuse a vacant building that has no room to provide parking. Many of these reuse opportunities are historic buildings. An additional economic development distortion is that because land prices are lower in suburban areas, the cost of complying with parking requirements is lower than in urban infill areas. Finally, parking requirements can skew the business mix in a retail area and hamper the development of new businesses on sites that do not have parking on each parcel. This is the case with restaurants, which are often an economically feasible use but cannot meet the high restaurant parking requirements on-site. This effect on the business mix may harm a traditional retail area that needs restaurants but ends up with clothing resellers because only they can meet the parking requirement.

Directly harm the environment

Parking requirements increase hardscape area, causing urban heat island effects, increased rainwater runoff, and reduced groundwater recharge. Parking surfaces collect polluted runoff because of leaking oil and other fluids from parked cars. Site hardscape reduces opportunities for groundwater retention, open space, tree planting, playgrounds, and other amenities on the site. To the extent that parking and roads are codetermined, the pollution and landscape impacts of parking and roadways have impacts on habitat, flora, and fauna by affecting contiguous wildlife areas, native species, water resources, and the like. Private vehicle transportation systems usually have a larger noise footprint, especially around major facilities. For pollutants such as fine particulates, there are concentrations around parking and transportation infrastructure. Finally, there are pollution and greenhouse gas emissions associated with parking construction activities.

Indirectly harm the environment

When parking requirements encourage driving over transit, walking, and bicycling, the result is more VMT and more traffic congestion. Private vehicle travel usually involves more energy use, more air pollution, higher greenhouse gas emissions, and more vehicle-related accidents. There are also environmental consequences associated with the extraction of fossil fuel energy used to power transportation systems and the energy and material extraction to build vehicles and facilities.

Disadvantage nondrivers

Parking requirements inhibit the emergence of market pricing because mandating a parking supply preempts a market process that would provide and price parking at the intersection of the supply and demand curves. The cost of parking, therefore, is hidden from the consumer. Instead, it is passed on in higher prices, more expensive housing, less business opportunity, and lower salaries at work. One might think that free parking is a boon for low-income drivers, who benefit by saving out-of-pocket costs. That is true, but those who walk, bicycle, or take transit pay higher rents, higher prices for goods and services, and receive lower salaries at work, to pay the costs of providing parking that they do not use. A socially inequitable cross subsidy is created, redistributing from those imposing the least environmental impact on society— those who do not drive— to those who create the greatest impact by driving. Furthermore, those without a car or who are unable to drive one have an access disadvantage. This includes worse access to jobs, especially from the center city to suburban jobs, fresh food, child care, medical care, educational opportunities, and other types of trips that contribute to social mobility. Cities with balanced, multimodal transportation systems provide a smaller penalty to those without private vehicle transportation. Zoning was initially championed as a progressive cause; it is ironic that parking requirements allocate some of the cost burden of accommodating those who park to those who do not park, such as those who access the site using transit, walking, or bicycling travel modes.

Lower physical activity with consequences for public health

To the extent that parking requirements favor private vehicle use they contribute to public health issues such as asthma, through air pollution, and personal inactivity, which is tied to obesity. Frank et al. (2004) found a positive association between each additional hour spent in a car each day and obesity (as measured by Body Mass Index, or BMI), and a negative relationship between each additional mile walked each day and BMI. That study also showed that mixed land uses are associated with lower obesity levels.

Imprecisely represent actual parking utilization levels

The ratios in parking requirements are often devoid of local empirical evidence and are not appropriate to local context and project characteristics. Local jurisdictions infrequently ask, “How much parking is actually used by existing land uses in the community?” Imprecision can occur in two ways. First, ratios may inadequately consider local area factors such as land use/ transportation conditions, parking pricing, income, economic objectives, and the like. Second, they may ignore issues about whether the land use category being considered has characteristics and parking utilization levels that are the same as an average land use of that type. In other words, is there something different about the use or class of uses being considered, such as differing employee density in office buildings or resident income levels in housing?

National averages are sometimes used to create parking ratios, but even the most commonly used source, the Institute of Transportation Engineers (ITE) Parking Generation handbook, cautions that the rates they provide are not ITE recommendations for parking requirements and counsels that the users of the information need to be “cognizant of the unique characteristics that can affect parking demand site-by-site” (2010, ix). The ITE authors note that “most of the data currently available are from suburban sites with isolated single land uses with free parking” (2010, 2). Most ITE rates have a suburban bias, and if used uncritically, they perpetuate parking oversupply. Shoup further complains that using national averages is “the misuse of precise numbers to report statistically insignificant estimates” because the sample size for some land uses is small (2003, 1).

An example of variability associated with local context is shown in the data provided in the Parking Generation handbook (2010). A medical office building (categorized by ITE as land use 720) would seem to be a standard use, with consistent parking utilization across many observations and locations. The ITE peak period parking rate is 3.2 vehicles parked per 1,000 square feet of gross floor area (GFA) (2010, 210). The ITE calculated this rate by averaging eighty-six studies of medical office buildings across the United States, completed from 1963 to 2009. The problem is that the range of observations is from 0.96 to 5.65 vehicles per 1,000 square feet of GFA, with a standard deviation of 1.22. This large variation means that there are large differences among the individual projects used to compute the average, whether it is the land use and transportation context or the project’s individual characteristics.

Another example of parking utilization variability relates to housing. The U.S. Census American Community Survey (ACS) asks households about their vehicle availability (U.S. Census Bureau 2012b). The results of this annual survey are differentiated by geographic area and by subcategories. Vehicle availability is not the same as parking utilization, but it is a predictor of parking utilization because it indicates the maximum vehicle accumulation if all available vehicles are parked at once (not accounting for visitors). Figure 2.2 shows the vehicles available per occupied housing unit for owner-occupied and renter-occupied units in the United States and five counties in New York State. These include the county that is New York City and nearby counties, encompassing a range of environments from high density to suburban. The range is striking, ranging from less than one-quarter vehicles per rental household in New York County to slightly over two vehicles per household in Nassau County owner-occupied, single-family homes.


Figure 2.2. Household vehicle availability in the USA and New York metropolitan area. Source: US Census data

The ITE Parking Generation handbook provides rates by five housing types, with some differentiation between urban and suburban areas. The rates are more uniform than the census data suggest, ranging between 1.03 and 1.83 vehicles per unit. Clearly, local variation in density, land use mix, transportation systems, and transportation costs influence household vehicle availability, and therefore parking utilization. Chapter 6 provides more detail on how this data can be used to develop residential parking requirements. As mentioned, parking utilization rates also vary by the characteristics of the occupants, whether that is by type of employee in an office building or the characteristics of residents of housing units. Figure 2.3 shows that household vehicle availability varies by household income, indicating that higher incomes predict higher levels of vehicle availability. Using the National Household Transportation Survey (US Department of Transportation 2009), the figure shows that the vehicle availability rate is less than one vehicle per household for incomes under $ 10,000 and then rises steadily with income. If parking requirements treat different forms of housing in the same way, regardless of income, projects that serve lower income residents will be forced to provide more parking than is used, which adds to project cost and harms affordability for this cost-sensitive population.


Figure 2.3. US household vehicle availability versus household income. Source: 2009 National Personal Transportation Survey


  1. Examples illustrated with 350 square feet per space (including drive aisles and ramps), 5 percent cost of money, thirty-year amortization of capital costs (land plus construction cost), 260 days of operation per year. No land costs are attributed to the underground parking example. Costs per space vary depending on landscaping requirements, soft costs, parcel configuration (affecting the efficiency of the design), site and soil conditions, local codes, and many other factors.


From Parking Reform Made Easy by Richard W. Willson. Copyright © 2013 Richard W. Willson. Reproduced by permission of Island Press, Washington, D.C.

About the Author

Eric Bethany A graduate of Tulane University in New Orleans, Louisiana, Eric Bethany joined KWA in 2015. In addition to contributing to the architectural activities of the firm, Eric works with principal Eric Kronberg to compile and publish research on KWA's Urban Space blog and helps manage KWA's marketing efforts.

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