What is the Harris-Ullman multiple-nuclei model and when is it used?

• A. The urban model with multiple centers of activity (nuclei) rather than a single CBD; applies to polycentric cities with several economic hubs.
• B. It is an urban model with a single central business district and rings.
• C. It is an old rural land-use model focusing on agriculture.
• D. It describes a linear city growth along a highway.

Answer: (A)

Cities can develop around several centers of activity rather than a single central business district. The Harris-Ullman multiple-nuclei model shows that different functions cluster around distinct nuclei—such as a university area, an airport, an industrial park, or a suburban shopping hub—each with its own surrounding offices, housing, and services. This pattern emerges as transportation improves, land farther from the crowded core becomes more available or affordable, and activities specialize around what each nucleus serves.

This model is used to describe polycentric metropolitan regions where multiple hubs drive growth, rather than one dominant downtown. It helps explain patterns of commuting, land use, and the emergence of sub-centers in large cities that have spread out and diversified their economic activities. Traditional monocentric models don’t fit cities with several strong centers, so this framework is especially relevant for many modern urban areas with multiple economic cores.