社区规划 —理论与实践 by xiuliliaofz


									Community Planning & Design
     Community Framework

 Community, like any structure, must have a framework that
  supports it and gives it physical form.

 Circulation system, both vehicular and pedestrian, are not only
  essential paths that allow movement, they are bones, if you will,
  around which the organism of community grows. Individuality
  & character.

 However, community planning continues to be predominantly
  influenced by the automobiles.
 After WWII, a modified or flexible grid system came into fashion due
  in part to its successful use at a planned unit development (PUD)in
  New York called Levittown. This in itself was a radical break with the
  tradition of the times.

 In the 1960s and 1970s, PUDs came to be more accepted, with far-
  reaching changes for society. Curvilinear roads, looping collector
  streets, short, curving cul-de-sacs, and a reliance on the hierarchical
  system became commonplace. This approach worked well until the
  PUDs in any given area began to build out and the inevitable traffic
  congestion resulted.
 In the 1980s, the exclusive community came into vogue.
 At the beginning of a new century, we are looking back to a simpler
  time and place. The neo-traditional town exhibits the traditional
  values of neighbors, friends and family, with a de-emphasis on
  automobile by attempting to enhance the pedestrian environment and
  promote mass transit.
 Vehicular circulation consumes an estimate 30% of our developed
  area. It is the most expensive feature of community development and
  creates vast expanses of pavement—literally a no-man’-land for the
 Is automobile inherently evil and destroying the planet? From a
  rational standpoint, down deep we all know the real problem lies not
  with our cars but with the way our towns and cities are structured.
 Automobile is such a strong influence and promises to be so for a long
  time to come, roads and parking must be approached calmly and
 Too often circulation is patterned after high-way standards, resulting in
  very costly, inflexible design.
 Creating discord and confusion? Harmonious unity, variety?
 Residential streets: intimate, foster interaction between neighbors;
  should not resemble micro-freeway.
 DISCUSS                  A                                      B
Basic Forms
On a neighborhood scale, circulation patterns in our developed areas
  generally take on one of four basic forms:

p Grid

p Radial

p Hierarchical

p Looping

More typically, each neighborhood will be designed by using a
  combination of two or more of these basic types.
 1). The grid system
   Is designed to disperse traffics as uniformly as possible by providing
    options for both pedestrians and vehicles. It has been much maligned
    due to its seeming rigidity, monotony and indifference to topography.
    It can be relatively easy to adapt it to its topography.

l Greek & Romans
l “gridlock”: thought of in
  terms of congestion and

l Used with frequency in
  US Midwest with
  abundance of level land.
The grid system (example 1)
 Predictability of intersection: gives travels clues and ref. points in way-

 Pleasant by-product: no need for collector streets
 San Francisco: Interesting
  triangular intersections and
  green spaces.
 Vertical space: skyscraper.
The grid system (example 2)
  New Orleans: grid system bending in response to Mississippi River,
   create a physical and psychological link to that great waterway.
The grid system
  Walkable for pedestrians ; a variety of ways;

  expensive and land-consuming;
--New York, Manhattan, 40-50% covered by asphalt pavements. Yet there is still
   never a parking space to be had!
2). Radial systems
 A series of street emanating from or
  focusing on a central point zone.
 Functionally, originate from farm-to-
  market roads where products and livestock
  were transported to a central area for sale
  or shipment.
 Works well to create a community heart or
  focus, thus functionally and figuratively
  unifying an area. It works best in
  combination with a set of circumferential
  roads that create concentric circles about
  the center.
 Allows the most direct route to and
  through the central point, leading to
  peaking periods of congestion at the central
Radial systems (example 1)
 Focused ~sprawling format
 Superimposed over a grid system to create dynamic spaces.
 Washington DC
 Radial systems (1)
    Most cities have some form of radial system emanating from the old
     city core, this system has not been applied to the outlying areas and
     probably should have been used as a design approach.

 Organic, less- planned
  core areas, London
 1930s,这片土地上
3) Hierarchical systems
 Branching system, is a pattern of
  circulation structured much like a tree in
  that smaller roads or branches lead to an
  increasingly larger collector roads.
 With the advent of Planned unit
  development (PUD), it came into design
  prominence in the 1960s. Persist in
  massive number today.
Hierarchical circulation system

 This concentration of traffic on fewer and fewer roads ensures an
  eventual overload of the system because it creates few, if any,
  alternative routes of access to a particular place. Instead, choke points
  are created, as there is essentially one way in and one way out of an

 Direct traffic into one or only a few points of circumferential
  movements, navigating around the choke points is very difficult.

 Isolate certain areas from the community at large; Reduce their
  psychological link with the community;
Hierarchical circulation system
  Rely on cul-de-sac streets; pull amenity into residential areas;   high-priced
   homes; in large area way-finding for visitors and residents can be exasperating
   as all areas tend to be the same. This problem can be overcome if an
   identifiable spine road or collector loop is employed to create a discernible
   structure that hold the system together.
 In small-scale residential environments consisting of a limited number
  of housing types and housing units.

 Also work well for areas adjacent to tidal waters, on lakes or in areas of
  substantial topography.

 All of these areas are typified by an undulating edge beyond which no
  development is possible; therefore, using cul-de-sacs or closes to branch
  off a neighborhood street is a typical solution. By keeping through traffic
  to a minimum, they help reduce noises and conflicts between
  pedestrians and automobiles at the extreme end of the system.

 Economical: allow the maximum amount of development area per
  minimum length of street.
   4). Looping Systems
 Can be readily utilized for individual
  neighborhoods than for community-wide
 When used in combination with hierarchical
  system, a strong sense of place can be achieved;
 Neighborhoods built using this format are usually
  typified by a primary entrance road that leads to a
  central organizing roadway from which the
  residential streets stem.
 Widely used in PDU because they provide a strong
  organizing framework;
 Despite the single-entry feature, this layout
  distributes local traffic better than the branching
  system, esp. the farther away from the entry one
Looping Systems
n Roadway widths can be smaller than those found in the hierarchical systems.
n However, as in the hierarchical system, all traffic is forced to a single point, with
  the end result being the same: traffic congestion;
n To a limited extent, this system can be applied in a linear fashion, esp. in areas
  where large through streets or highway bisect an area, with access to adjacent
  areas limited by topography, wetlands, or water.
n In these instances, the primary role of such a system is to provide additional right
  -of-way frontage for development and to provide for a parallel access system to
  the main road; this system has been widely adapted to successfully create linear
  office parks along major thoroughfares: exposure to and visibility from the main
  road are possible, while access to the office sites are channeled and controlled at
  few points. This allows the larger traffic volumes on the primary roadway to be
  separated from the traffic around the office site. The gains from such flexible
  access are lost by the inability to identify a center or focus for the development
the Strengths and Weaknesses?
  Our communities and neighborhoods have been structured using one
   or more of the four basic circulation patterns. Whether this has been
   in response to such things as topographic anomalies, wetlands, or the
   locations of existing utilities, we need evaluate the strengths and
   weaknesses of these patterns to determine how they can help create
   the types of community framework we want.
Classifying Streets
 The function of a street dictates its classification, this in turn dictates
  its design volume and construction requirements.

 Tight street grids           wider streets are the norm; streets have
  become solely the domain of automobile, communities have lost their
  uniqueness, their sense of individuality, their sense of place. The grid
  pattern has faded from use and the alley has become all but extinct in
  suburban realm.
 CSD Pattern
 In conventional suburb development (CSD), street classification has
  evolved, and has come to be defined in hierarchical terms, each type
  representing a higher volume of vehicular traffic. This has produced three
  primary types of streets: minor streets, collector streets and arterial

 Minor streets: 12-16m, 2 lanes, directly serve residential home-sites;

 Collector streets: 18- to 32m, 4 lanes, connect residential areas to arterial

 Arterial streets: ≥32 meters, designed for the movement of high volumes
  of traffic between nodes with commercial and industrial functions. Four
  or more lanes with median in the center. Generally, no dwellings front
  directly onto the arterial streets.
TND pattern
(traditional neighborhood development)
 Use the following terms:

Ø Neighborhood streets: two-way vehicular movement, no separating
  median; planting verge for tree and a side-walk; parallel parking.

Ø alleys: lanes, no sidewalk;

Ø drives: separate a developed area with non-developed area.

Ø roads

Ø avenues: equivalent to CSD collector road

Ø boulevards: equivalent to CSD arterial streets, with median in the center
  separating opposing travel lanes, no on-street parallel parking;
Design considerations
 Principles: not hard and fast rules, they are desirable design
    approaches that can lead to better communities.
ü   Identify areas where roads cannot be placed; marshes, steep slops,
    historic/cultural places of significance, etc.
ü   Determine desired points of destination from the site and lay out
    internal circulation system accordingly.
ü   Promote access and land use integrity within community;
ü   Through traffic should be separated from local/residential traffic but
    should remain part of the community;
ü   It is generally less costly as well as less destructive to the land to lay out
    roads parallel to topographic contours or at right angles to them;
ü   Historically, emphasis has been placed on patterns designed to reinforce
    the separation of uses; however, this leads to further traffic
    concentrations that rely on only a few through streets.
ü   Conscious effort needs to be made to reinforce, not sever, the ties
    between residential areas and their supporting commercial and office
Technical Considerations
 Refer to 《城市道路与交通》
 城市道路设计规范》

 A number of technical parameters are
  either commonly accepted as standards
  or dictated as mandates; every
  municipality has adhered to slightly
  different standards that must be verified
  prior to any design.

 The amount of traffic must be considered
  when designing a road network in a

 Horizontal and vertical curve,
Broken-back curve

 Broken-back curves and reverse curves are
  usually designed with at least 31 m tangent
  or straightway between them to allow
  recovery time for motorist and additional
  braking space.
 Refer to 《城市道路与交通》& 《城市道
 At-grade intersection
 Rotary intersections
 In commercial and office area alike, parking
  bays should be oriented toward the buildings.
 Landscape islands
 Angular parking system is inefficient.
 Avoid a parking that does
  not provide a turnaround.
Public utilities
 Service;

 Water

 Sanitary sewer

 Storm water management

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