Because each cohousing community is planned in its context, following the principles of complementary architecture. A key feature of this model is its flexibility to the needs and values of its residents and the characteristics of the site. Cohousing can be urban, suburban or rural. The physical form is typically compact but varies from low-rise apartments to townhouses to clustered detached houses. They tend to keep cars to the periphery which promotes walking through the community and interacting with neighbors as well as increasing safety for children at play within the community. Shared green space is another characteristic, whether for gardening, play, or places to gather. When more land is available than is needed for the physical structures, the structures are usually clustered closely together, leaving as much of the land as possible "open" for shared use. This aspect of cohousing directly addresses the growing problem of suburban sprawl.