By Marta Polovin
Parking is at the epicenter of a complicated relationship between land use and transportation. The way a city is planned, developed and regulated plays a pivotal role in people’s need to drive and/or buy a car. These choices have staggering climate, economic and social equity implications. As of 2018, California is not on track to meet its 2020 greenhouse gas reduction target under SB 375. This is largely due to more people driving more miles than ever before (CARB 2018). In the U.S., parking is the result of decades of land use decisions that have prioritized automobility, often to the detriment of creating sustainable and accessible cities; put simply, regulations have focused on using space for private vehicle storage rather than for people (Shoup 2005). Parking is known to be an enabler and simultaneous product of sprawl, contributing to air pollution, congestion, and other negative externalities associated with driving (Litman 2006).
How independent or dependent we are on vehicles is largely a function of how we manage residential parking. One of the biggest determinants of driving, unsurprisingly, is vehicle ownership. Consequently, one major determinant of vehicle ownership is the availability, ease and cost of parking at home. However, residential parking is largely overlooked in published literature and often not critically or deeply studied by cities. A vast majority of parking research is concentrated on transportation demand management (TDM) strategies for reducing the total number of vehicle trips to a workplace, but these studies largely ignore the residential realm (Guo 2013; Weinberger 2012; Marsden 2006). Additionally, there is even less knowledge regarding on-street parking and its relationship to vehicle ownership. From a policy perspective, how can we make data-driven and informed decisions about reducing car dependency when we are missing key pieces of information about residential parking and vehicle ownership?
In order to address this gap, the San Francisco Municipal Transportation Agency (SFMTA) has embarked on a comprehensive residential parking study. The SFMTA oversees on-street parking policies along the public right-of-way, including the Residential Parking Permit (RPP) program. In 1976, RPP was established to improve quality of life in residential neighborhoods impacted by the spillover effects of major traffic generators. RPP grants permits which only allow nearby residents to park on the street during the day. In San Francisco alone, approximately forty-four percent of households live within an RPP area (SFMTA 2017). The SFMTA is interested in knowing how policies like RPP would impact the effectiveness of recent parking policy changes aimed at reducing vehicle ownership in densifying neighborhoods. The findings below provide some background and framing for the study.
What is Known About Residential Parking and Vehicle Ownership
Residential parking roughly is divided into two categories: off-street (in a private garage or driveway) and on-street (in the public right-of-way). A majority of the limited studies conducted on residential parking focus on off-street parking. Historically, off-street parking requirements (parking minimums for new developments) have resulted in far too much parking availability which induces sprawl, vehicle dependency and higher costs of housing (Shoup 2005). Parking minimums require that developers build enough parking to accommodate the periods of highest demand; and these assumptions are often arbitrary and derived from suburban contexts (Shoup 2005). A single parking underground parking spot can cost around $70,000 to build in San Francisco. Cities like San Francisco have begun to remove parking minimums and in some cases implement parking maximums. Currently, in San Francisco, it is unknown how reductions in off-street parking will impact on-street parking. Some of the key findings regarding off-street parking supply and vehicle ownership are summarized below:
- The presence of off-street parking encourages higher rates of vehicle ownership and driving (Rowe et al. 2013; Weinberger et al. 2008). One study estimated that private access alone triples the likelihood of vehicle ownership (Christiansen et al. 2017).
- For Transit Oriented Development (TOD) projects, accessibility to high quality transit was not a significant predictor of vehicle ownership after off-street parking was accounted for (Chatman 2013); and while TODs do help lower auto trips, they do not decrease car ownership rates when there is parking available (Cervero et al. 2010).
- When the price of parking is baked into the price of housing (bundled), rather than paid separately (unbundled), it induces higher vehicle ownership rates (Manville 2016; The Planning Center 2013; Ter Schure 2012).
- In areas with no parking requirements (minimums or maximums) developers were more likely to build parking in areas with excellent public transit service as compared to areas with lower density and poorer transit accessibility (Guo & Ren 2013).
On the other hand, what is known about residential on-street parking and vehicle ownership is primarily from a few studies done in New York City (where there is no RPP or other policy mechanism for explicitly pricing for residential parking) and Europe (which faces different political and normative challenges). However, available findings tend to mirror research conducted on off-street parking:
- Households tend to own fewer cars when there is less on-street space for parking and when it is priced (Guo 2013; Broaddus 2010; De Groote et al. 2016).
- Households with easily accessible on-street parking were two and a half times more likely to park on the street, even when factoring in garage and driveway space (Guo 2013a).
- Free, accessible on-street parking is linked with people turning their private garages into storage units for items other than cars and, in some cases, accessory dwelling units (ADUs) (Taylor 2018; Brown 2007).
- When on-street parking is plentiful and available, vehicle ownership rates increase by eighteen percent even when transit is accessible (Guo 2013).
While limited, these findings highlight how on-street residential parking availability can promote vehicle ownership. However, many unanswered questions remain about the relationship between RPP programs and vehicle ownership. Ultimately, on-street parking belongs to the public right-of-way and there is, “Little consensus on exactly why on-street parking is provided”(Guo 2013). A vast majority of on- and off-street, residential parking in the U.S. is free, which is a tacit incentive to buy and drive a car (Shoup 2016). And often, when things are “free” or “a given”, they often go unnoticed and unquestioned, which leads to short-sighted policies and strategies for tackling broader environmental, economic and social challenges.
Parking comes with real costs for our climate, transportation infrastructure and communities. Moving forward, the way we manage on-street residential parking will have enormous implications for the wellbeing of our growing cities. If a household can easily and/or cheaply store a car at home, owning and driving a car is a convenient choice.
Some preliminary policy recommendations for cities include:
- Continuing to remove parking minimums & supporting parking maximums
- Unbundling parking for all new residential projects
- Studying residential, especially on-street, parking policies & their relationship to vehicle ownership
The results of the SFMTA RPP study will be key towards informing policies that advance the agency’s goal of “connecting San Francisco through a safe, equitable, and sustainable transportation system” by providing new insights into the effect of RPP policies on vehicle ownership and use. In recognizing the privileges that RPP grants residents with vehicles (especially for those that live in lower density housing), it is vital that San Francisco’s curb space is utilized to advance broader agency goals, rather than private vehicle ownership and usage. In thinking about our knowledge gap regarding residential parking and vehicle ownership, we will also need to enact just, equity-based policies that support residents that have historically borne the brunt of our auto-dominated transportation and land use systems. Future parking actions will need to recognize and ameliorate impacts on lower-income households who are reliant on vehicles due to a lack of transit accessibility in their neighborhoods and/or who have limited choices in where they can afford to live. Without critically evaluating our residential parking landscape and having the data to back future decisions, cities cannot comprehensively address broader issues of climate, land use and transportation equity.
Marta Polovin is a second-year Master of City Planning candidate at UC Berkeley’s College of Environmental Design.
Acknowledgement: Kathyrn Studwell, SFMTA Program Manager of Residential Permit Parking, provided invaluable feedback and extensive feedback on this literature review.
The views expressed in this article do not necessarily represent those of the Berkeley Public Policy Journal, the Goldman School of Public Policy, or UC Berkeley.
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