Mixed-use development:

 is the practice of allowing more than one type of use in a building or set of buildings. In planning zone terms, this can mean some combination of residential, commercial, industrial, office, institutional, or other land uses. The concept of "mixed-use" as a discrete zone is predicated on the relatively recent practice of single-use zoning wherein uses in all other parts of a community are widely separated by legislative mandate.

Throughout most of human history, the majority of human settlements developed as mixed-use environments. Walking was the primary way that people and goods were moved about, sometimes assisted by animals such as horses or cattle. Most people dwelt in buildings that were places of work as well as domestic life, and made things or sold things from their own homes. Most buildings were not divided into discrete functions on a room by room basis, and most neighborhoods contained a diversity of uses, even if some districts developed a predominance of certain uses, such as metalworkers, or textiles or footwear due to the socio-economic benefits of propinquity. People lived at very high densities because the amount of space required for daily living and movement between different activities was determined by walkability and the scale of the human body. This was particularly true in cities, and the ground floor of buildings was often devoted to some sort of commercial or productive use, with living space upstairs.

This historical mixed-used pattern of development declined during industrialisation in favor of large-scale separation of manufacturing and residences in single-function buildings. This period saw massive migrations of people from rural areas to cities drawn by work in factories and the associated businesses and bureaucracies that grew up around them. These influxes of new workers needed to be accommodated and many new urban districts arose at this time with domestic housing being their primary function. Thus began a separating out of land uses that previously had occurred in the same spaces. Furthermore, many factories produced substantial pollution of various kinds. Distance was required to minimize adverse impacts from noise, dirt, noxious fumes and dangerous substances. Even so, at this time, most industrialized cities were of a size that allowed people to walk between the different areas of the city.

These factors were important in the push for Euclidian or single-use zoning premised on the compartmentalization of land uses into like functions and their spatial separation. In Europe, advocates of the Garden City Movement were attempting to think through these issues and propose improved ways to plan cities based on zoning areas of land so that conflicts between land uses would be minimized. Modernist architects such as Le Corbusier advocated radical rethinking of the way cities were designed based on similar ideas, proposing plans for Parissuch as the Plan Voisin, Ville Contemporaine and Ville Radieuse that involved demolishing the entire center of the city and replacing it withtowers in a park-like setting, with industry carefully sited away from other uses.

In the United States, another impetus for Euclidian zoning was the birth of the skyscraper. Fear of buildings blocking out the sun led many to call for zoning regulations, particularly in New York City. Zoning regulations, first put into place in 1916, not only called for limits on building heights, but eventually called for separations of uses. This was largely meant to keep people from living next to polluted industrial areas. This separation, however, was extended to commercial uses as well, setting the stage for the suburban style of life that is common in America today. This type of zoning was widely adopted by municipal zoning codes.

With the advent of mass transit systems, but especially the private automobile and cheap oil, the ability to create dispersed, low-density cities where people could live very long distances from their workplaces, shopping centres and entertainment districts began in earnest. However, it has been the post-second World War dominance of the automobile and the decline in all other modes of urban transportation that has seen the extremes of these trends come to pass.

In the 1920s, the U.S. National Zoning Enabling Act of 1923 and a series of National Subdivision and Planning acts in English-speaking countries first set forth standards and practices of single-use zoning to be adopted by every municipality, which soon became the standard for all post-World War II development. These laws enforced and codified standards for modernsuburban design as it is known today, which have been exported to many other countries through planning professionals and transportation engineers. The resulting bills progressively included restrictions on alleyways, minimum road widths, restrictions on cross streets for major arteries, buffer zones between separate areas, and eliminating mixed-use in all new developments, resulting in a moratorium on traditional urban development which remains in place in most areas that are not specifically zoned as "mixed use" or "general urban development".

Drawbacks

Mixed use development is often seen as too risky by many developers and lending institutions because economic success requires that the many different uses all remain in business. Most development throughout the mid to late 20th century in the United States was single-use, so many development and finance professionals see this as the safer and more acceptable means to provide construction and earn a profit. Christopher B. Leinberger[citation needed] notes that there are 19 standard real estate product types that can obtain easy financing through real estate investment trusts. Each type, such as the office park and the strip mall, is designed for low density, single use zoning. Another issue is that short termdiscounted cash flow has become the standard way to measure the success of income-producing development, resulting in "disposable" suburban designs that make money in the short run but are not as successful in the mid to long term as walkable, mixed use environments.

Mixed use commercial space is often seen as being best suited for retail and small office uses. This precludes its widespread adoption as the trend to ever-larger corporate and government employment accelerates.