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Thread: Optimal permeability between high-density mixed-use and low-density residential

  1. #1
    Cyburbian
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    Optimal permeability between high-density mixed-use and low-density residential

    This subject arose in the recent discussion about fenced and unfenced yards. And, I was wondering if anyone could elucidate as to the leading schools of thought on the matter.

  2. #2
    Unfrozen Caveman Planner mendelman's avatar
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    "Optimal permeability" - you need to define that term

    Plus when you post threads, especially in the professional forums put more effort into the initial post to warrant/garner interest and replies.
    I'm sorry. Is my bias showing?

    The ends can justify the means.

  3. #3
    Cyburbian
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    Are you talking about surface runoff? I'm lost.
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  4. #4
    Cyburbian
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    Here are the two applicable postings from the other thread:

    Originally posted by cng
    Nice examples with your photos. I see that these homes face onto what looks like a collector street, and led me to think... how do residential subdivisions with perimeter walls fit into the transect concept? I feel like I'm about to go off on a tangent here... but do New Urbanist developments inherently assume a grid circulation pattern? If so, I can see how perimeter walls can be done away with in these types of developments. In the exurban city that I work for, our General Plan policies call for more connectivity, however, we (in particular, the city's engineers) are not quite ready to forgo residential perimeter walls, which isolates residential homes from other uses. At best, we achieve a modified-grid layout where you may achieve a grid pattern within the perimeter walls--hence, still restricting access onto arterial streets, but allowing more grid-like blocks within.
    I assume crime is the primary concern.

    My neighborhood is currently attempting to combine some citizen planning through non-governmental, civil-society organizations with the City's planning, which includes a Transit-Oriented Development Overlay District that The Planning Center is now crafting with assistance from Cooper Carry. So, this issue is of particularly-timely import to us from the perspective of people who are currently living with a largely-unrestricted regular grid that has a hierarchy of streets.

    Based on the limited knowledge I have of such things, the more urban, mixed-use areas benefit from greater density with lower crime levels that are provided by increased eyes on the street and eyes from the street, especially since these areas can become regional or metropolitan draws that inhere a greater number of strangers. Lower-density areas are not as capable of providing that type of surveillance, and these places, presumably, would, as such, benefit by limiting the regional or non-local traffic, ideally in a way that does not make for a less pedestrian-friendly environment.

    New Urbanists generally take the Jane Jacobs view that barriers create problems, although she limited her discussion to metropolises with residential densities that are uniformly high. I am a little more circumspect. Ease of egress from a low-density neighborhood may be correlated with higher crime rates. So, perhaps, the issue of automobile permeability needs to be separated from pedestrian, bicycle, and Neighborhood Electric Vehicle (N.E.V.) permeability.

    Limiting the number of automobile access points from a low-density area, then, is probably advisable, but doing so may not have to impair connectivity for pedestrians and cyclists or for N.E.V. users. Fusing the grid for cars in certain places and making definite edges with strong gateways, as well as passive and/or active surveillance, makes sense to me, as does filling the spines that lead to these automobile exits with traffic-calming measures. But, I'm speaking beyond my depth. The issue of permeability probably deserves its own thread.

  5. #5
    Cyburbian
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    I can't find these photos. Can you link them?

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  7. #7
    Cyburbian
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    I know, for example, that Duany, historically, has argued in favor of a mix of uses in all the Transect Zones and that gates and other barriers be removed. But, I've also read studies that show limiting regional automobile traffic in low-density areas lowers crime levels.

    Some people have argued in favor of fusing the street grid for automobiles while keeping it unrestricted for pedestrians and cyclists, as well as for N.E.V. users, conceivably. And, I tend to agree with this school of thought, but I know others disagree because traffic increases on streets that lead to the few exits and that these thoroughfares necessarily must be wider and less pedestrian-friendly. I counter that there are other ways to calm traffic.

    There's also some question as to where maximizing eyes on the street and a mix of uses is best and where more restrictions on access and more limitations on the diversity of uses make sense.

    Also, if there are a limited number of entrances to and exits from the low-density areas, how strong do the gateways need to be and what kinds of surveillance are necessary? Are any unintended consequences created?

    Additionally, how do the transitions between the sub-urban and more urban Transect Zones need to be handled.? I've seen studies that show rowhouses are among the best housing typologies for these areas since they are, by far, the safest. Where is the synthesis that combines the advantages of the New Urbanism with those of suburban sprawl?

  8. #8
    Cyburbian
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    Quote Originally posted by Pragmatic Idealist View post
    Here are the two applicable postings from the other thread:
    Thanks PI.

    Well.. you can always try to do it the way we do it in San Diego. 1950-1970s proto-suburban 5 to-an-acre single family homes, right next to 20 storey residential and office towers, right next R&D parks and factories, all right up to the lot line.

    Transects, planning and urban design are overrated. Have money (or a promise of jobs), will have variance...

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    Cyburbian Raf's avatar
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    Quote Originally posted by Cismontane View post
    Thanks PI.

    Well.. you can always try to do it the way we do it in San Diego. 1950-1970s proto-suburban 5 to-an-acre single family homes, right next to 20 storey residential and office towers, right next R&D parks and factories, all right up to the lot line.

    Transects, planning and urban design are overrated. Have money (or a promise of jobs), will have variance...
    True Mixed-Use..lol
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  10. #10
    Cyburbian
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    Quote Originally posted by CPSURaf View post
    True Mixed-Use..lol
    Yeah, 'cept they make it so pedestrian-hostile, that the only way to get between the two adjacent parcels is to drive ;-P

  11. #11
    Cyburbian Raf's avatar
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    Quote Originally posted by Cismontane View post
    Yeah, 'cept they make it so pedestrian-hostile, that the only way to get between the two adjacent parcels is to drive ;-P
    heh it happens

    I'm still trying to figure out the point of this thread...
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  12. #12
    Cyburbian cng's avatar
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    Cities evolve and densities change over time. Whatever that gets built, the circulation pattern designed should accommodate any future evolution (likely, densification) of that community. The grid-pattern is still the pattern that lends itself to transitions and evolution. Fenced-off neighborhoods and restricted access are harder to deal with it over time. In other words, a more permeable framework with open access offers more choices for the future, since you can always close some off later, or turn them into one-way streets, etc... than, starting out with restricted access and trying to open them up later.

  13. #13
    Cyburbian
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    I generally agree, but let's say, for instance, that the streets are laid in a grid configuration and bollards are placed here and there to control automobile access.

    Some of them might even be automated and retractable in order to provide access to residents, and their guests, exclusively.

    The bollards can be removed as the area grows, but, today, they are doing the job of keeping regional traffic from having easy ingress, and especially egress, from the low-density, mostly residential areas, where residents need to know who happens to be a stranger and who belongs there.

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    Cyburbian
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    Is there a happy medium between gated communities and the New Urbanism?

    If sociologists have found that, to prevent deindividuation, and the pathologies it creates, the optimal size of a community is 30,000-35,000 residents, then community dividers seem like a good thing, if the population is sufficiently varied, especially in terms of income.

    Cities have been surrounded by walls for centuries, and close-knit communities are probably necessary in sub-urban areas where community self-policing requires a different approach than in dense mixed-use environments. Eyes on the street and from the street are not sufficient. So, more insulation is necessary. Stronger edges and gateways, as well as community dividers, seem, on their face, to be desirable to me in these conditions.

    I think the realization people should make is that cars facilitate a significant number of the crimes in sub-urban places, so limiting the ability for automobiles to escape the scenes of these crimes can help to deter potential perpetrators; whereas, I imagine bicycles and N.E.V.'s are simply too slow and too limited in their ranges to pose the same threats. And, pedestrians, likewise, can't get very far on foot.

  15. #15
    Cyburbian
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    Quote Originally posted by CPSURaf View post
    heh it happens

    I'm still trying to figure out the point of this thread...
    Here we go... from our suburbia. How to do single family detached homes to highrise multi-unit to highrise commercial mixed use to industrial, all in a mile.. throwing in a regional mall for good measure.

    http://maps.google.com/maps?q=san+di...45362&t=k&z=15

    Here's an outer suburban area with similar characteristics:

    http://maps.google.com/maps?q=san+di...22681&t=k&z=16

    Note that each clustered area of similar uses and densities - whether single family detached, multi-family, retail, office park, R&D campus, etc., are effectively walled villages all to themselves. The residential ones are usually gated.

    Planning abortions.
    Last edited by Cismontane; 23 Nov 2010 at 3:47 PM.

  16. #16
    Cyburbian
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    Now, I know why driving in that area makes me want to shoot myself.

  17. #17
    Cyburbian
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    Quote Originally posted by Pragmatic Idealist View post
    Now, I know why driving in that area makes me want to shoot myself.
    I like walking around those neighborhoods, just to make a point. But I always feel like I might get arrested, since clearly one is not supposed to do that.

  18. #18
    Cyburbian jswanek's avatar
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    Are "sustainable" new urban forms supported by most people?

    In 2010, Cal Poly San Luis Obispo researchers chose to examine the question of whether people considered principles of “sustainability” to actually be beneficial.

    http://digitalcommons.calpoly.edu/cg...&context=focus

    Surveying their own student General Education population, they found that, whereas 94% thought “greening” was good for humans, along with 86% for better solar-oriented building designs, and 80% approval for more safe bike paths, ONLY 8% thought higher density living was a good thing, 26% supported neighborhood “compactness”, with 35% in favor of social diversity, 38% for mixing land uses together, and only 41% for mixing single and multifamily, market and affordable housing together.


    Note: Future planners and architects were far more supportive of all these things.

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