Difference between revisions of "Generative Module for Smart Code"

Summary of major email posts in this work:

• • • MM outlines specifications from paper on Chris Alexander work:

What are the elements of such a generative code? We can broadly summarise them here:

1. The code, in some way, specifies a step-wise, generative process. 2. It specifies that in that process, human beings will take certain rule-based actions, in combination with evaluations based upon feeling, and in adaptation to what came before. 3. At each step, it acts upon the then-existing condition as a whole. 4. At each step, it identifies the weakest parts of the structure and acts to improve and amplify them. 5. At each step, it may apply previously-coded solutions and patterns, and adapt them to the novel conditions. 6. At each step, it differentiates the space by specifying new "centres" 7. The centres are differentiated via 15 "structure-preserving transformations" 8. Infrastructure follows. As with the morphogenesis of organisms, where the tissues come first, and the veins and ducts follow, the human patterns and human spaces come first, and then transport, sewers and the like follow – not the reverse. 9. Similarly, visual expression follows. The human patterns come first, and then the visual ideas and "signifiers" follow – not the reverse. Otherwise we are simply making people live in disconnected sculptures, however worthy as such. 10. At the end of each cycle, the result is evaluated and the cycle is repeated.

• • • Andres Duany replies:

See if you can build it on these. There is a regional-scale and a community scale process in the appendix of the SC

DESIGNING A GREENFIELD SITE

Greenfield sites are similar enough that they may be designed according to a standard protocol, as follows. See Appendix XIX for a New Community Evaluation form.

Step One: Map the existing evidence on the land. Assimilate the traces of the site into the plan. Traces include paths, roads, ponds, woods, slopes, streams, and wetlands. Design the parks and squares around ponds and wooded areas or specimen trees as much as possible, so that mature trees grace the public spaces of the community from the outset. Further define natural boundaries by excluding arterials, utility easements, slopes exceeding 25%, and preserved lands.

Code: see Section 2.3 and Section 2.4 for Regional Plans, Section 3.2.1 for New Community Scale Plans, and the Environmental Module.

Step Two: Identify the type of Community Unit to be designed. A greenfield site may be developed under a New Community Plan as one of three Community types:

Clustered Land Development (CLD), also known as a Hamlet, appropriate for a location on a simple thoroughfare, therefore destined to have a weak commercial component.

Traditional Neighborhood Development (TND), also known as a Village, suitable for crossroad locations. A Village is the design equivalent of a complete urban neighborhood, albeit standing free in the landscape.

Regional Center Development (RCD), also known as a Regional Center, town, or town center, which should be planned around a regional transportation nexus considered capable of sustaining the equivalent of a shopping mall. A Regional Center supports substantial commercial development, including both retail and office, as well as residential and civic functions. RCD should be adaptable to light rail or Bus Rapid Transit (BRT). These transit options need not be present before the project is complete, because transit may follow development as well as lead it.

Code: see Section 2.2.4 for Regional Plans and 3.2 and 3.3 for New Community Plans.

Step Three: Locate the mixed use center on the thoroughfare or intersection with the most traffic.

There are two schools of thought about locating mixed use centers (town squares and main streets). One option is simply to locate the commercial center on the thoroughfare or intersection with the most traffic, even if it is not at the geometric center of the site, because without traffic the retail elements may wither. (One exception is a location of such compelling interest - a beach, the base of a ski run, or a spectacular public viewshed - that traffic would be drawn to it as a destination.) The other option is commonly exercised when the location with the most traffic is a large arterial thoroughfare which may undermine the social performance of the place. In that case it may be advisable to insert the mixed use center some distance into the neighborhood.

Step Four: Roughly structure the site into Pedestrian Sheds. Pedestrian Sheds determine neighborhood size, with their types dependent on the Community Unit types. Thus neighborhood size is determined by walkability, not by density, which is a function of the regional location and the market. Density may be as low as three units to the acre for a rural Hamlet and as high as 80 units to the acre for a Regional Center. All are structured on the neighborhood pattern of Pedestrian Sheds.

Each Pedestrian Shed is equivalent to a five-minute walk from edge to center. The Pedestrian Shed is conventionally drawn as a circle scaled to a quarter mile radius, representing the average distance that most people would walk rather than drive to a destination. It is more accurately drawn as an irregular shape reflecting actual walk times. For infill, the sheds can be measured by walking the actual thoroughfares, though this is rarely done; for greenfield design, walk times must be estimated based on the plan and the topography.

Orient one of these sheds on the previously determined mixed use center. Arrange any additional Pedestrian Sheds to cover the remainder of the development site without substantial overlap. The more the catchments of the sheds overlap, the more they tend to compete with each other and dilute each other's viability as mixed use centers, unless a composite shed is planned with centers whose functions complement each other instead of competing.

Step Five: Precisely adjust the location of the Pedestrian Sheds. The centers of the Pedestrian Sheds should meaningfully coincide with traces on the land.

A cluster of specimen trees may become a central green, and a rise or ford may provide another. Hedgerows may provide trees for avenues, and country stone walls should remain alongside new roads. Existing country paths and lanes embody the geographic experience of animals and persons; they should influence the trajectories of new thoroughfares wherever possible. A certain easy beauty will result from assimilating such traces of the land.

This process requires a skillful designer's eye as well as a "lucky site." Several designers should work on these proposals independently, because a single eye is less likely to find the key unlocking the character of a site that supports strong neighborhood structure.

Where traces are not determinants, introduce a public space or special intersection as the center of each Pedestrian Shed.

Code: See Section 3.2 Sequence of Community Design, Section 3.5 Civic Zones, and Section 3.7 Thoroughfare Standards.

Step Six: Connect the neighborhood centers with larger thoroughfares. At this point, the natural traces have been assimilated into urbanism, the main mixed use center has been determined, and the neighborhood structure has been outlined by Pedestrian Sheds. Now, connect these neighborhood centers to each other with larger thoroughfares, known as main streets or avenues. These should be direct, but not necessarily straight. Most thoroughfares should deflect in response to the land's traces or to slow traffic.

Next, fill in the area between these main thoroughfares with secondary routes, known as streets and roads, in a network pattern. These in-between areas need not be geometrically coherent throughout the entire Community Unit, but may be localized.

Networks must be adjusted to create a block pattern that is smaller and more permeable when close to a center, and progressively larger elsewhere. Then subdivide the block pattern into lots that also become larger relative to the buildings that occupy them, so the ratio of nature to building becomes progressively more rural towards the edges of the Community Unit. This is the beginning of a transect.

Code: See Section 3.7 Thoroughfare Standards.

Step Seven: Detail the other urban elements so they all support Transect Zones.

The Transect used in the SmartCode analyzes and coordinates the built environment. It works by coordinating the typical elements of traditional urbanism; those that are rural in character support each other, and those that are urban support each other. The Transect creates a diversity of natural and human habitats, providing choice according to the needs and preferences of residents. Hamlets (CLD) and Villages (TND) display Transect Zones evolving from rural edges to urban centers. Regional Centers (RCD) may invert the sequence, with the more urban areas on major thoroughfares along the edges of neighborhoods. This gradient, when rationalized and subdivided, becomes the basis of SmartCode zoning. Customize Article 5 and Table 7, Table 8, Table 9, and Table 15 to create the block and building scale details for the Community Unit. An analysis of regional typological and architectural character should guide any customization of the SmartCode elements. The framework of thoroughfares and open space creates the image and structure of the town. The engineering and the detailing of these elements, including paving, landscaping, lighting and furnishing, must be determined by the planner according to their Transect location - even if built over time.

Code: see Article 6 Table 1. Manual: see Outline of the Code.

Step Eight: Reserve the Civic Sites. Civic institutions are necessary to the well-being of a community, yet are often difficult to provide. The market generally encourages private residential and commercial buildings, but not civic buildings, which accommodate educational, governmental, recreational, religious, or cultural institutions. A New Community Plan provides for them by reserving civic sites at each neighborhood center for local institutions. For each TND, there should be places reserved for, at minimum, an elementary school, childcare facility and Meeting Hall. For an RCD, the plan should also designate sites for regional institutions such as secondary schools, government agencies, religious and cultural buildings. If such Civic Zones are preserved in perpetuity by the Regulating Plan, the residents themselves will, over time, bring the civic buildings into being. Covenants are necessary to ensure this.

Code: see Intent Section 1.3.2 The Community and 1.3.3 The Block and the Building, and Sections 3.5 and 5.4 Civic Zones.

Step Nine: Provide Covenants and Establish Local Governance A community requires local governance for which a set of covenants must be written. They should be enacted by contract as a condition of the purchase of a lot or a building. In typical Home Owners Association (HOA) documents, such covenants are usually conceived to protect the prerogatives of the development agency, assigning all power to itself. Consequently, the community remains hobbled by its system of governance, unable to adjust organically to society, culture and the economy as they evolve. Instead, these covenants should provide for an elected executive with considerable influence (a role initially played by the developer), balanced by a small deliberative body and an appellate forum. This Community Association must have the capacity to levy charges that provide for the ongoing maintenance of the public realm (e.g. Civic Space, Civic Buildings, Thoroughfares). A portion of the charges should also be allocated in trust for civic improvements, allowing the community over time to decide how to best to invest them on the reserved civic lots. These covenants must also make reference to the code that guides the ongoing construction of the community.

Step Ten: Establish a Community Association At some point during the buildout of the community -- after the general direction has been set, but while meaningful adjustments are still possible -- the original planners and developers should withdraw in favor of the Community Association, which should include a Town Architect's office staffed by those who live in the community. For it is only by participating in the daily life as citizens that municipal administrators have standing in the community they govern. Those who must move on have undergone an apprenticeship in community building, the lessons of which may be applied elsewhere.

REGIONAL PLANS (This example is taken from north Hillsborough County, Florida.)

Step 1 Identify lands where development should not occur. Land where development is already not permitted is assigned to O-1 Preserved Open Sector. Land that should be protected, but is not yet, is assigned to O-2 Reserved Open Sector.

Step 2 Identify lands where development should occur. First, assign G-4 Infill Growth Sector to land already urbanized. Second, assign G-3 Intended Growth Sector to high capacity intersections and transit proximity. Third, assign G-2 Controlled Growth Sector to areas adjacent to medium capacity thoroughfares. Last, assign G-1 Restricted Growth Sector to all land remaining on the Sector map. The TDR option may be utilized in this Sector, depending on state enabling legislation.

Step 3 Prioritize G-3 Intended Growth Sectors for development and designate Transfer of Development Rights receiving areas. The O-2 Reserved Open Sectors are designated sending areas. Once their development rights are transferred, these areas join the O-1 Preserved Open Sector. Land in O-2 that has not had its rights transferred may be designated as G-1 Restricted Growth Sector.

Step 4 - Conclusion The O-2 Reserves have become O-1 Preserves; the Reserves remaining with untransferred rights have been designated G-1 and may be developed as CLD, and the new TND and RCD Communities are in the G-2 and G-3 Growth Sectors.

Note: The G-4 (Infill Growth) Sector is assigned to Infill and Redevelopment as specified in Article 4. It may be developed as TND or RCD. The following are specified in Article 3: The G-1 Restricted Growth Sector may be developed as CLD; the G-2 Controlled Growth Sector may be developed as CLD or TND, and the G-3 Intended Growth Sector may be developed as TND or RCD.

• • • Besim Hakim Proposal - using generative procedures for the back areas (mews etc) while using more "classical" form-based codes for the streets and frontages:

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I think it can be done but would require a lot of work to make it work. Maybe the current SC can be called the Classical SC and the one we are discussing may be called the Vernacular SC. Some of each might need to be incorporated in the other to make them mesh together and work well with each other. Each one might take a prominent role to the other depending on the nature of the project. In any case some calibration might be necessary to the particular as one tackles specific projects. Besim

• • • Sandy Sorlien reply:

   Date: Mon, 16 Feb 2009 10:54:45 -0500
   To: , , ,

   , 
   From: Sandy Sorlien 
   Subject: Re: Conceptual suggestion for incorporating generative process

Hi Besim, cc others

In your diagram, there are some unhatched areas on the frontages. Are you intending that all the private frontages be C, or only public frontages? I can't tell if the blank areas are for sidewalks or private frontages.

If the private frontage is part of C, then this approach has possibilities. While in this country we would have a lot of difficulty with the chamfered buildings (I hear that builders can't or won't do them, too expensive), the SmartCode is not much concerned with what happens behind the private frontages - behind what we call the First Layer. The only exception to that is parking, which differs by Transect Zone.

If the V Vernacular code generates things like side window placement, "clogging" of backbuildings and outbuildings, and minor lot subdivision to get that wonderful Charleston-like density tucked back away from the primary thoroughfares, then we might have a good combination. Call it the Backstreet Code...?

Sandy

   --
   Sandy Sorlien
   Director of Technical Research
   Center for Applied Transect Studies
   http://www.transect.org/

   Bungalow Studio
   340 Gates Street
   Philadelphia, PA 19128
   215-487-2716 main
   215-480-3115 cell
   215-487-3599 FAX
   http://bungalowstudio.org/

   Calibrate local.

• • • Besim reply:

Hi Sandy, Conceptually the way I see it: -- the blank areas are for buildings fronting the public realm, public or private. They have to follow the Classical SC. Do not be concerned with chamfered buildings. I am only using Krier's diagram to make my point. -- the hatched areas for the Vernacular SC (which I hatched on Krier's diagram) would need its own Vernacular code and following a generative process different from the Classical SC. This needs to be fully developed from the ground up and your take on it in your third paragraph below is about right. So what we end up with is control of buildings facing the public realm following strict prescriptive codes, and within the Vernacular areas people will have freedom to shape the micro built environment. The role of the developer and the overall production process will be different from current practice, but must be developed to work with the parameters of the current system. Besim