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Analyzing Infill Development Potential
By William Fulton and Ryan Aubry, Solimar Research Group

Over the next 20 years, California will add six million jobs. Those jobs will draw 12 million people to the state, and they will need four million new homes. The way the state will accommodate this additional population and economic activity is likely to be different than in the past.

In the past, California absorbed additional population and economic activity through sprawl—auto-oriented, suburban communities and developments typically built on undeveloped land at the metropolitan fringe. For example, between 1970 and 1990, the population of the state grew by 45 percent, while urbanized land increased by 200 percent.

In the last 10 years, this situation has begun to change, especially in California's older coastal metropolitan areas where land for new development has become expensive and precious. Traffic congestion has rapidly increased and has made sprawl on the metropolitan fringe a less feasible strategy than before. In addition, the environmental consequences of low-density sprawl on the fringe have become more apparent.

As a result, the concept of infill development—the development of new homes, commercial areas, and public facilities on vacant or underutilized land in existing communities—is now considered a viable alternative to sprawl development in many parts of the state.

As the need for infill development grows throughout California, so does the need for analytical tools that help identify prospective infill sites and estimate the potential of infill development to meet the state's need for housing and other urban development.

Infill raises a host of new issues, such as environmental justice, that transportation and community planners must address. In addition, California communities face two major obstacles in implementing infill strategies. The first is identifying appropriate infill sites in a rigorous manner. The second is persuading state housing officials that unconventional infill locations, such as areas along commercial strips, should be accepted as part of the housing policy.

Under California law, all cities and counties must produce a Housing Element. This is a section of the General Plan that outlines programs and policies designed to permit the community to meet housing production targets set by the state and regional agencies. Although the Housing Element typically contains a vacant land inventory, developers have found this list to be of limited value. Furthermore, state officials have been reluctant to give full credit to infill sites. Of course, simply identifying infill sites is no guarantee that infill development will actually take place because other policies may be required to stimulate development.

The California Infill Estimation Tool enables local governments, developers, and community groups to overcome these obstacles by helping

  • Local governments create a more rigorous screening mechanism for infill parcels.
  • Developers short-circuit the windshield survey by identifying promising parcels up-front.
  • Policy makers determine how much infill development will be stimulated by infill policies such as higher densities and greater subsidies.

The California Infill Estimation Tool provides local jurisdictions, developers, and community groups with a flexible method for identifying parcels that might be ripe for infill development. It also provides a method for testing the likely success of different infill strategies. Users can incorporate a wide variety of data, including both parcel- and district-level data, and conduct analyses at almost any geographic scale from parcel to county level.

This tool was developed by a team of public agencies and planning consultants under an Environmental Justice Grant made by the California Department of Transportation to the city of Los Angeles. It was designed using off-the-shelf software and operates with a combination of ArcGIS and Microsoft Excel. It contains two separate features—the Geographical Screening Feature and the Infill Strategy Evaluation Feature.

With the Geographical Screening Feature, users can select parcels within a given geographic area that meet specified criteria. It highlights those parcels on a map or an aerial photograph and calculates statistical information for the selected parcels such as acreage and maximum build out under current zoning. The feature operates in ArcGIS.

The Infill Strategy Evaluation Feature lets users test the likely effect of specific infill strategies such as higher densities or financial subsidies. Users can determine how infill development will be stimulated by the adoption of specific strategies such as a density bonus, transit-oriented development, and mixed-use development along commercial strips.

About the Authors

William Fulton is the president of Solimar Research Group of Ventura, California. He may be contacted at Ryan Aubry is the chief GIS analyst for Solimar Research Group. He may be reached at

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