increases. According to this method, deviations from this expected pattern would qualify an area as a potential center. As noted, the literature tends to define centers in terms of employment densities. This definition is narrower than the goals of PSRC’s Centers policy, which is to foster the development of mixeduse areas, with housing included among other land uses. McMillen (2003) notes that “results [from previous studies] suggest that subcenters may still be primarily a non-residential phenomenon” (p. 2). Including residential population and/or housing in a centers analysis will require moving beyond the methods used to define employment sub-centers in much of the literature. Using a threshold of activity unit density rather than employment density will help correct this deficiency. Others are suggested by Moudon and Hess (2000), who have identified suburban locales with high residential densities in the Central Puget Sound region. Moudon and Hess found “that the region contained 85 [suburban residential] clusters, twelve of which contained “between 5,000 and 8,800 people” (p. 247). They also noted that “the average cluster’s net population density could easily reach 40 persons per acre or higher” (p. 247, emphasis original) – more than three times the average activity unit density of urban census tracts in the region. Recognizing these residential clusters as potential centers may help correct for an over-emphasis on employment. One preliminary conclusion from this cursory review of the academic literature is that place matters on a sub-regional scale. Academics have noted that different employment density can be expected at different distances from an historical Central Business District, while defining centers in contrast to their immediate surroundings. It follows that different designation criteria may be appropriate in different sub-regions in a larger metropolitan region such as the Central Puget Sound. For example, counties in the region could set different activity unit density thresholds when establishing criteria for sub-regional center designation. However, to be a center as defined in much of the literature reviewed for this report, a location must have higher employment density than the immediately surrounding area. Finally, in studying regions where centers are not designated by policy, scholars have defined centers according to observed characteristics. The focus of academic studies on actual conditions indicates the importance of longitudinal monitoring of densities and other conditions in designated centers to determine whether they have maintained their economic viability and central importance from the time of designation. Planning in other regions This study of planning in other regions focuses on planning efforts by Portland, Oregon and Vancouver, British Columbia. Each of these areas employs the urban center concept in their planning process. The following sections summarize strategies for each region. Portland, Oregon The Metropolitan Services District in Portland, Oregon designated 38 centers according to its 2040 Growth Concept, the long-range plan for future growth. It’s ‘2040 Growth Concept’ was developed in the 1990s in consultation with an extensive public outreach process and the input of local agencies. The plan divided the region into conservation and growth areas, and created an urban design typology for each development type. Each typology is associated with goals and standards. Typology designations include a tiered system of center development ranging from Regional Center Planning in the Central Puget Sound
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