Final answer:
An overlay zone or district such as a local school district serves special functions within a larger government, and examples of urban planning models include the concentric zone model and sector model that demonstrate socioeconomic and functional organization within a city.
Step-by-step explanation:
An example of an overlay zone or district is a special district such as a local school district, which is designed for a specific function and can exist within larger municipal or county boundaries to provide specialized services. These overlay zones are often found in heavily populated areas where county and city governments might be overwhelmed. There are several models to describe the spatial structure of a city, one of which is the concentric zone model introduced by Burgess in 1925. This model subdivides a city into areas that radiate from the center, with different zones representing areas like business districts, residential areas, and industrial sectors.
Another relevant model is the sector model, which includes an elite zone characterized by upper-class residences often situated along significant boulevards or waterfronts, with industry and transportation routes creating sectors where lower-income populations are likely to live. Both models illustrate how specific types of overlay zones or districts can be planned based on socioeconomic and functional criteria to organize urban space effectively.