What are Cores, Centers and Corridors?

Victor Gruen's diagram of potential cores in a region only hints their potential number and variety of sizes and locations.¹

"Americans are creating the biggest change in a hundred years in how we build cities. Every single American city that is growing, is growing in the fashion of Los Angeles with multiple urban cores."  - Joel Garreau

The terms "core" and "center" are used here interchangeably to describe a concentrated and compatible mix of urban land uses that serves as a node of activity within a city or region. The historical expression of this concept is the typical downtown containing a variety of land uses usually centered on retail services.

Such concentrations of development (often poorly- or un-planned) have emerged around suburban shopping centers in most metropolitan areas. Joel Garreau describes this in his book, Edge City, starting with the words quoted above. They are variously described as Major Diversified Centers (MDC's)," Major Activity Centers (MAC's), and Edge Cities.

Garreau defines them as relatively large concentrations of development, with five million square feet of office space and 600,000 square feet or more of retail space. However, as conceived here, cores or centers can be created at any scale and anchored by many different functions.

Although cores as described by Garreau are important, something different is envisioned here. At city or regional scale nearly every major shopping, educational, medical government, recreational, office or research facility has the potential to attract and serve as the focus for related development. In most cases, the principles suggested for planning cores whether retail-focused or otherwise should apply equally to centers and cores of every size and type. And benefits should be similar regardless of what the main anchors are.

This is partially illustrated in the Chicago 2040 Plan⁴ prepared by Chicago Metropolis 2020 (a NPO created by The Commercial Club of Chicago) for the Chicago area (2005) (see the Northeastern Illinois Planning Commission 2040 Plan website and the Chicago Metropolis 2020 website).

Not strongly reflected in the Chicago 2040 Plan, however, is the concept that virtually every concentration of activity has the potential for being a mixed-use core – and should likely be one. If this concept were to be followed the number of cores could more than double. Adding two million to the population as projected would make the number even greater. And recognizing all “hamlets” would add even more. However, applying a strong core’s policy may concentrate growth sufficiently to reduce the amount of sprawl and the number of cores otherwise needed. The Chicago 2040 Plan does mention a category of “special places” such as airports, national laboratories, etc. of the scale of a “metropolitan core but which may not qualify as such in the Chicago 2040 Plan's definition. A good argument could be made that facilities of this type should be required to develop as mixed-use cores and to follow principles and concepts for sound core design and management.

The term "corridor" describes a series of cores or centers (or would-be cores) strongly connected by one or more modes of transportation. Ideally, these nodes or centers should be developed in accordance with principles described here, but with the added feature of strong transportation links to other cores. Linking of cores with highly effective transportation enhances each and all of them by connecting and aggregating available opportunities, resources and populations.

This Phoenix model suggests that cores be created at neighborhood, community and village levels.

In addition to those listed above, the term "Polycentric City" has been coined to describe the concept of a region of interconnected centers. Dr. Jerry B. Schneider conducted major studies of this concept in the 1970's.³ His key findings are reflected in many areas of this web site.

It is urged that development of mixed-use centers be used as a planning strategy for smaller geographic areas such as neighborhoods or communities. Usually the smallest of cores, these have received relatively little consideration in planning and research. They are often mainly retail in function and are seldom compactly arranged or designed. Also they are often built as "strip" centers with little attention to the planning principles recommended here.

Relatively few of the tens of thousands of existing centers (or corridors) conform to sound planning principles. Older downtowns, originating before the era of auto dominance and containing facilities of wide cultural and community value and with good leadership, will be more likely meet these principles and to be successful in any revitalization effort.

Where basic planning principles, such as good access, compactness and internal circulation cannot or are not being applied, older downtowns often fail. Or, they, along with potential new centers, sprawl well beyond any ability to function effectively. Although most centers are accessible by car few have the mix and balance of uses, the compactness or the amenity and ease of internal circulation required to make them effective. The results are levels of congestion, cost, confusion and discomfort that greatly limit their ability to work effectively - and frequently blight surrounding communities.

These deficiencies make it important that more people become aware of the value and importance of developing cores and of the principles that will helping do this. Much information defining and describing cores, centers and corridors may be found in the links shown.

¹Gruen, Victor, Centers for the Urban Environment, Van Nostrand Reinhold, 1973

²Garreau, Joel, Edge City: Life on the New Frontier, Doubleday, 1991

³Schneider, Jerry, Transit and the Polycentric City, U. S. Department of Transportation, 1981

⁴Northeastern Illinois Planning Commission, 2040 Regional Framework Plan, 2005

⁵Goals for the Chicago Central Area, Chicago Central Area Committee, City of Minneapolis Planning Department

⁶Goals for Central Minneapolis, Its Function and Design, 1959, and Minneapolis Metro Center, Planning Principles, 1979