The most recent major development in zoning has been the introduction of form-based zoning. The idea originated in the 1980s but has become widespread only in the last decade or so. As will be seen, form-based zoning codes are more flexible than traditional zoning in some ways but considerably less flexible in other ways.
Traditional zoning codes specify which uses are permitted and provide basic numbers for matters like floor area ratio (FAR), maximum building height, minimum parking space, and setbacks from property lines. For most places that use traditional zoning, the number of zones is quite large and there is a tendency for the number of zones to increase with the passage of time. Although traditional zoning imposes many requirements, it does not specify directly what the ensuing development will look like. Form-based zoning, by contrast, places the emphasis on the physical form of the development—on what the area in question will actually look like— and, as compared to conventional zoning, is much more flexible about permitted uses. It is consistent with neotraditional design, as discussed in Chapter 10, and, not surprisingly, many of its proponents are of the neotraditional school.23
One of its originators and most prominent proponents has been the neotraditional architect and urban designer Andres Duany (see Chapter 10). One way he has presented the form-based approach is through the idea of an urban transect (a term the dictionary defines as "to cut across" or to "dissect transversely").24 Imagine a line drawn from the rural periphery to the center of a city or metropolitan area. The line will pass through a variety of types of development, each of which has a more or less characteristic form, as shown in the diagram on page 161. Along this transect, moving inward from the periphery, are defined six zones: 
The first two zones in the list make the transect complete, but it is the last four zones that are important for this discussion.
The proponents of the form-based approach take the view that for each of these zones there is a desired form and that the goal of land-use controls is to move development toward that form. The form-based zoning code defines areas on the map and then specifies a number of design criteria that the developer must meet in each zone. It is intended to specify quite closely what the area will actually look like and be like to spend time in. So far as the aesthetics and the feel of an area are concerned, the use of a form-based zoning code shifts a considerable amount of the decision from the individual builder or developer to the planner or urban designer. To the extent that form-based codes often originate in a community "visioning" process, the public—or at least that part of the public that participates in the process—has a much greater say in the final product.
As a document, the form-based code looks very different from a traditional zoning code. The traditional code is predominantly words and numbers. It may contain an occasional diagram to help the reader understand the numbers or any calculations that must be made from them. The form-based code, on the other hand, is heavily pictorial, since its message to the developer is "this is what it should look like." Because there are only a few zones, rather than the multiplicity of zones in a traditional ordinance, it is likely to be a simpler and more readily comprehended document.
What are some of the items that are regulated? Like a traditional code a form-based code will specify maximum heights. Unlike a traditional code it will often specify minimum heights, since one of the goals of most form- based codes, in keeping with neotraditional design philosophy, is compact, walkable development. Like a traditional code, a form-based code will specify setbacks. But where the traditional code will simply specify a minimum setback, the form-based code may specify exactly what the setback must be, or in some zones it may specify that there be no setback—that the building come right up to the building line. Form-based codes will also specify items not found in traditional codes, such as placement of entrances and details about doors, windows, and courtyards. In some cases form- based codes may specify which materials are acceptable for the cladding of the walls of buildings or which materials are acceptable for roofs when roofs are visible from the street. The form-based code will include specifications about sidewalk width, radius of curbs, and the planting of trees, in some cases even down to acceptable species.
In the ways just described, the form-based code is clearly much more restrictive and directive than the traditional code. On the other hand, it is much less restrictive with regard to permitted uses and will generally specify only very broad categories of use, such as residential. Unlike the traditional code there is not the multiplicity of zones, but just a few basic types. In that sense the form-based code is less complicated.
FIGURE 9-1 The six
zones of the urban transect as visualized by Andres Duany.
Source: Duany Plater- Zyberk & Co.
Figure from Duany Plater- Zyberk & Co. Copyright © by Duany Plater- Zyberk & Co. Reprinted with permission, courtesy of Duany Plater-Zyberk & Co.
More often than not, form-based codes are applied to only a part or parts of the municipality. Form-based zoning is likely to work best where there is still a substantial amount of room for building. If an area is largely developed, the amount that can be achieved with a form-based zoning code will be limited. Perhaps the best environment for form-based zoning is a new community, where the planner or urban designer starts with a clean slate. Form-based zoning is relatively new, so at this point it is premature to pass judgment on it.
The writer has heard developers complain, perhaps justly at times, that if only zoning were more flexible, they could do better and more creative work. Will we someday hear them complaining in the same way about form-based zoning? Planner and land-use lawyer Donald L. Elliot suggests:
As with most good ideas, the strengths of form-based zoning are also its weaknesses. Its advantages in communicating intended patterns of development also make form-based zoning a relatively static tool. Unlike PUDs, which can always be negotiated to reflect the latest trend in development and architecture, or performance zoning, which might be satisfied in different ways as new technologies emerge in the future, form-based zoning is more of a snapshot tied to the present. Although proponents make a fairly strong case that there is a semiobjective difference between "good" and "bad" design forms, only time will tell whether they are right. . . . If all the neighborhoods met the requirements . . . theoretically resulting in a residentially perfect city—would it become a cliche? Would we see buyers start to demand something else just to be different? . . . The jury is still out as to whether form-based zoning is more or less time bound than other forms of zoning.25
-  Rural preserve 2. Rural reserve 3. Suburban 4. General urban 5. Urban center 6. Urban core.