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Over-building of parking supply leads to increased automobile ownership, vehicle miles traveled, congestion and housing costs. In addition, it presents barriers to smart growth and efficient transit service. King County Metro has an interest in encouraging land uses, policies, and development that overcome these barriers and lead to communities that transit can serve efficiently and effectively. Parking supply and pricing often have a direct impact on jurisdictions ability to create compact, healthy communities.

By providing locally credible and context-sensitive data on parking demand, our region has the opportunity to:

  • Support economic development by reducing barriers to building mixed-use multi-family residential developments in urban centers near transit infrastructure;
  • Reduce housing costs as well as household monthly expenditures allowing a larger demographic to participate in the urban, infill housing market;
  • Encourage use of transit, rideshare, bike and walk;
  • Reduce vehicle miles traveled (VMT) and greenhouse gases (GHG).

Who will benefit?

Developers, public decision makers, and communities will all benefit from the outcome of this project. With updated context-sensitive information on parking demand, cities can regulate development in way that meets local and regional goals and developers can build more housing near transit.

Contact us

Metro Transit Division
King County Department of Transportation
201 South Jackson Street
Seattle, WA 98104-3856

Daniel Rowe
Market Development, Service Development
Send Daniel an email
or call 206-477-5788


The Right Size Parking Project will achieve the following objectives through coordinated work with our partners and continual feedback from regional stakeholders including the Urban Land Institute and local jurisdictions.

Flowchart showing the concept of the old parking model versus the Right Size Parking model

The project will:

  • Provide context-sensitive multi-family residential parking demand information on a website to guide stakeholders decisions about building new parking and managing existing parking.
  • Offer incentives to jurisdictions and developers to test pricing and right-sizing of parking supply in residential and commercial developments;
  • Engage the development community through professional forums to utilize new parking demand information and implement pricing and management techniques.

Parking calculatorUpdated Sept 2018

The King County Right Size Parking Calculator is a map-based web tool that lets users estimate parking use for multi-family developments, in the context of specific sites. The calculator can help analysts, planners, developers, and community members weigh factors that will affect parking use at multi-family housing sites. It will help them consider how much parking is "just enough" when making economic, regulatory, and community decisions about development.

Screen shot showing VIA pointers

The Calculator is based on a model using current local data of actual parking use collected in 2012 and 2017 at over 200 developments in urban and suburban localities in King County, Washington. The parking use data is correlated with factors related to the building, its occupants, and its surroundings- particularly transit, population and job concentrations. The user adjusts the scenario using variables related to the building and its location, including proximity to transit, jobs and population. Understanding the influence of these variables helps determine how much parking is "just enough" for a particular site.

The Calculator was updated in 2018 using new data collected in 2017 around the County, making the model more robust and up-to-date. Since releasing the first version of, several things have happened that motivated King County Metro to update the tool. Development patterns have changed across the county, including high growth, significant investment in transit, and changing demographics. Now, along with all the features of the previous version, a user can vary the proposed multifamily housing development’s parking supply and see how that affects the modeled parking use. The sample size for the new regression model is now 260 buildings and the model can predict about 85% of the variation in parking use (R2 is 85%).

While it is intended to help support and guide parking supply and management decisions, it should not be viewed as a definitive answer. Rather, it should be seen as a resource to inform discussions, weigh the factors impacting parking demand, and help consider the proper provision of parking.


Pilot Programs

Right Size Parking is undertaking a series of demonstration projects that build on the research and analysis phase of the project, transforming key findings and concepts into real-world applications. These pilot projects are driven by stakeholder engagement and fit into one of two categories:

  • Policy-based pilots work to align jurisdiction parking regulations with regional goals. Through a competitive bid process, four King County cities were selected as partners and are now working with RSP staff and consultants to analyze potential policy changes.
    • Kent: Identify best code and management strategies for mixed use areas in the suburban context.
    • Kirkland: Establish parking requirements that reflect market demand and prevent spillover.
    • Seattle: Evaluate existing policies and programs, explore private shared parking opportunities.
    • Tukwila: Identify parking strategies for TIBS station-area; explore private shared parking.
  • Pricing-based pilots test parking pricing with innovative parking management and Transportation Demand Management (TDM) strategies, and will begin in early 2014. Four partners were recently selected through a competitive bid process: Capitol Hill Housing, El Centro de la Raza, Hopelink, and Zipcar. The details of these pilots are currently being solidified; more details will be added here as they become available.

Related research

We would like to thank the following partners

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