Do Cities Have Too Much Parking?

ACCESS Magazine 49

Minimum parking requirements create more parking than is needed. This in turn encourages more driving at a time when cities seek to reduce congestion and increase transit use, biking, and walking. After nearly a century of development under these requirements, parking now dominates our cities.

To counter the problem of excessive minimum parking requirements, academics and practitioners have advocated a new suite of parking policies, including reduced parking requirements and demand-based prices for on-street parking. These policies aim to better manage parking and reduce driving, but too much parking works against these goals by spreading the destinations and making the cost of driving artificially low. To more effectively address the issues caused by minimum parking requirements, planners and policymakers should focus not only on future development, but also on the existing parking oversupply.

Relatively little information exists, however, on the amount and location of parking in cities, limiting our understanding of how that parking contributes to land and automobile use patterns. To address this knowledge gap, we developed a case study to estimate where parking infrastructure exists in Los Angeles and how it has evolved over time.

(Note: this article focuses expands on the implications of our Journal of the American Planning Association publication Parking Infrastructure: A Constraint on or Opportunity for Urban Redevelopment? A Study of Los Angeles County Parking Supply and Growth)

Parking Infrastructure: A Constraint on or Opportunity for Urban Redevelopment? A Study of Los Angeles County Parking Supply and Growth

Journal of the American Planning Association, 81(4), pp. 268-286, doi: 10.1080/01944363.2015.1092879.

Many cities have adopted minimum parking requirements but we have relatively poor information about how parking infrastructure has grown. We estimate how parking has grown in Los Angeles County from 1900 to 2010 and how parking infrastructure evolves, affects urban form, and relates to changes in automobile travel, using building and roadway growth models. We find that since 1975 the ratio of residential offstreet parking spaces to automobiles in Los Angeles County is close to 1.0 and the greatest density of parking spaces is in the urban core while most new growth in parking occurs outside of the core. 14% of incorporated land in Los Angeles County is committed to parking. Uncertainty in our space inventory is attributed to our building growth model, onstreet space length, and the assumption that parking spaces were created as per the requirements.

The continued use of minimum parking requirements is likely to encourage automobile use at a time when metropolitan areas are actively seeking to manage congestion and increase transit use, biking, and walking. Widely discussed ways to reform parking policies may be less than effective if planners do not consider the remaining incentives to auto use created by the existing parking infrastructure. Planners should encourage the conversion of existing parking facilities to alternative uses.

Parking Infrastructure and the Environment

ACCESS Magazine 39

Little is known about how parking infrastructure affects energy demand, the environment and the cost of vehicle travel. Passenger and freight movements are often the focus of energy and environmental assessments, but vehicles spend most of their lives parked. Abundant free parking encourages vehicle travel and is thus a major incentive to auto travel and urban congestion. Abundant free parking also discourages public transit, walking, and biking. The technique of transportation life-cycle assessment (LCA) allows us to understand the full costs of travel including the energy use and environmental effects of parking infrastructure. Past LCAs, however have focused on evaluating the resources used for travel and have ignored resources use for parking. This focus is understandable given the diversity of parking spaces and the lack of available data on parking infrastructure. For example, consider the great differences in energy use and emissions associated with a curb parking spaces, multi-story garages, and private home garages. Furthermore, because causality between parking supply and automobile travel flows occurs in both directions, determining the energy use and environmental effects of a specific automobile trip (say a strip mall) is not possible. We develop a range of estimates of the U.S. parking space inventory, determine construction and maintenance energy use and environmental effects, and evaluate these results in the life-cycle of automobile travel. We find that the for many vehicle trips the environmental effects of the parking infrastructure sometimes equal or exceed the environmental effects of the vehicles themselves.

(Note: this article focuses on the policy implications of our Environmental Research Letter's publication Parking Infrastructure: Energy, Emissions, and Automobile Life-cycle Environmental Accounting)

Parking Infrastructure: Energy, Emissions, and Automobile Life-cycle Environmental Accounting

Environmental Research Letters, 2010, 5(3), doi: 10.1088/1748-9326/5/3/034001

The US parking infrastructure is vast and little is known about its scale and environmental impacts. The few parking space inventories that exist are typically regionalized and no known environmental assessment has been performed to determine the energy and emissions from providing this infrastructure. A better understanding of the scale of US parking is necessary to properly value the total costs of automobile travel. Energy and emissions from constructing and maintaining the parking infrastructure should be considered when assessing the total human health and environmental impacts of vehicle travel. We develop five parking space inventory scenarios and from these estimate the range of infrastructure provided in the US to be between 105 million and 2 billion spaces. Using these estimates, a life-cycle environmental inventory is performed to capture the energy consumption and emissions of greenhouse gases, CO, SO2, NOX, VOC (volatile organic compounds), and PM10 (PM: particulate matter) from raw material extraction, transport, asphalt and concrete production, and placement (including direct, indirect, and supply chain processes) of space construction and maintenance. The environmental assessment is then evaluated within the life-cycle performance of sedans, SUVs (sports utility vehicles), and pickups. Depending on the scenario and vehicle type, the inclusion of parking within the overall life-cycle inventory increases energy consumption from 3.1 to 4.8 MJ by 0.1–0.3 MJ and greenhouse gas emissions from 230 to 380 g CO2e by 6–23 g CO2e per passenger kilometer traveled. Life-cycle automobile SO2 and PM10 emissions show some of the largest increases, by as much as 24% and 89% from the baseline inventory. The environmental consequences of providing the parking spaces are discussed as well as the uncertainty in allocating paved area between parking and roadways.