"Communities across the country are increasingly recognizing that the spread out patterns of growth, which have shaped American communities for the past several decades, cannot be sustained. Problems of lengthy commutes, overextended public facilities and increased infrastructure costs, loss of farmlands, open space, and other valued community resources, and even reduced physical activity and community health are typically associated with such patterns. Instead, an increased emphasis on developing passed-over parcels within developed areas, and on maximizing use of existing public facilities is needed. Many communities have adopted urban growth boundaries that restrict the amount of land outside of urban centers that is available for urban development. The reduced land supply has created new interest in infill development opportunities in central and suburban cities alike.
Infill development is the process of developing vacant or under-used parcels within existing urban areas that are already largely developed. Most communities have significant vacant land within city limits, which, for various reasons, has been passed over in the normal course of urbanization. Ideally, infill development involves more than the piecemeal development of individual lots. Instead, a successful infill development program should focus on the job of crafting complete, well-functioning neighborhoods. Successful infill development is characterized by overall residential densities high enough to support improved transportation choices as well as a wider variety of convenience services and amenities. It can return cultural, social, recreational and entertainment opportunities, gathering places, and vitality to older centers and neighborhoods. Attention to design of infill development is essential to ensure that the new development fits the existing context, and gains neighborhood acceptance. A cooperative partnership between government, the development community, financial institutions, non-profit organizations, neighborhood organizations and other resources is essential to achieve infill success. In the long view, the public and private costs of continuing to favor sprawl development patterns will far exceed the resources needed now to facilitate infill development." Municipal Research and Services Center (MRSC) in Washington State.