Roadbuilding unleashes a chain of detrimental effects on the natural world. Cars produce greenhouse-gas emissions; roads produce sprawl; sprawl necessitates more cars; more cars need more roads; the cycle continues.
What's been less fully explored is the effect of building parking for all those cars. Or, more accurately, building surplus parking. According to a surprising new study out of Purdue University, parking spaces "in a midsize Midwestern county" (Tippecanoe) actually outnumbered cars three to one. Because the study did not count every floor in multi-level parking garages, the actual number was probably higher, with those excess spots including oversized suburban lots in front of strip malls, driveways and residential carports; and parking garages to serve large office parks.
All told, there were eleven times more parking spaces in Tippecanoe than there were families -- taking up space equivalent to more than 1,000 football fields.
Why do Americans have so many parking lots? One reason is we're lazy: people don't like to walk very far, so businesses overcompensate by providing excess parking. (The sight of cars circling suburban parking lots to find a space just a few feet closer to the entrance is a common one at suburban strip malls across America.) For another, parking seems to drivers like a limitless good, because they're largely insulated from its cost: in many suburban areas and small towns, parking is free, and even in urban areas, the dollar per hour it may cost to park is far from the true cost of construction and maintenance. So because parking appears to cost next to nothing, people use it freely, without regard to the social, economic, and environmental impacts of building a parking garage instead of, say, a storefront.
And those costs are troubling. Parking lots collect pollutants -- including heavy metals -- on their impervious surfaces. When it rains, those pollutants combine with stormwater to create polluted runoff, contaminating groundwater, streams and other water bodies, and water supplies. Moreover, parking lots contribute to the urban heat island effect, in which large, horizontal surfaces (like parking lots) reflect more heat back into the immediate atmosphere, making some urban neighborhoods two to three degrees Celsius hotter than surrounding areas. Parking lots also lead to bad land use policies: replacing storefronts with lots or garages leads to "dead zones" along the street, and plentiful parking encourages car-oriented development, roads, and sprawl.
One policy shift that could immediately cut back on the excess of built parking would be getting rid of minimum parking requirements, which are currently mandated to a wide range of land uses across America -- everything from condominium developments to diet clinics to wastewater treatment facilities. The Institute of Transportation Engineers' manual for determining parking requirements contains assumptions about how much parking is necessary that are generous, to say the least: two parking spaces per employee at daycares and preschools; three spaces per thousand square feet for food stores, financial institutions, and government and private business buildings; eight per thousand square feet for restaurants.
Some cities, including San Francisco and Seattle, have already reduced or eliminated minimum parking requirements in certain parts of their urban cores. Last year, Seattle eliminated or lessened the off-street parking requirements for businesses, and reduced some residential parking requirements as well. San Francisco not only eliminated parking minimums for downtown housing, it established maximums, and required that parking be sold separately from residential units so that those who don't want parking spaces don't have to pay for them. San Francisco also instituted land-use policies that bar garages at street level unless they include sidewalk-facing retail storefronts; limited the size of garage doors; and mandated one space for carsharing vehicles per every 200 residential units.
Another move that cities could make that would have an immediate impact on demand for parking is to make parking prices reflect the true cost of this amenity. According to a 1998 study by the American Planning Association [PDF], demand for parking went down by 23 percent when employees had to pay for parking (as opposed to having it provided by employers at no charge). Some call this social engineering. However, since the true cost of parking is almost never reflected in what cities charge (except in places like the Richmond suburb of London, which charges for parking based on emissions), the real "social engineering" is subsidizing cars -- through parking minimums and free or reduced-price parking.
