As readers of this Blog know, there is nothing we like better than new, precise words and phrases.

We also like familiar words and phrases used in new ways to help illuminate human settlement pattern-related relationships.

In his posts, Jim Wamsley has been using the term “Sweet Spot” to identify the low point of the Cost of Services Curve – the Second Natural Law of Human Settlement Pattern.

Sweet Spot is a great way to describe the low point of the Cost of Services Curve.

The Cost of Services Curve is plotted in the X Positive / Y Positive quadrant. The cost of a unit of services is scaled up on the Y axis and the density is scaled right on the X axis.

All the 40 +/- location-variable costs of services needed / demanded to support a quality contemporary life style start high at the lowest density (e.g. a power distribution system to serve 50 acres lots) and lower as the density increases.

At some point every one of those services starts back up. The bottom of the curve is the Sweet Spot.

We use transport as the canary in the minefield of dysfunctional human settlement pattern and each mode of transport has its own Sweet Spot.

For private vehicles in common use in 2000 (and still in 2007), the Sweet Spot is 10 persons per acre at the Alpha (Balanced) Community scale.

For shared vehicles with “high” capacity (e.g. METRO, MARTA, Metro, The Underground, U-Bahn, Subway) the Sweet Spot is 100 persons per acre at the Alpha Village (Station Area) scale.

(NB every word in the prior two sentences has a specific meaning.)

Depending on the size of the New Urban Region the private vehicle Cost of Service Curve rises from the Sweet Spot at different trajectories.

Depending on the configuration of the of the shared-vehicle system (and for very large New Urban Regions the mix of systems) the Cost of Service Curve also rises at different trajectories.

Given the dominance of private vehicles (The Autonomobile) in contemporary settlement patterns in the US of A, we use 10 persons per acre at the Alpha (Balanced) Community scale as the minimum sustainable density.

One other point:

In economic systems it is useful to think of maximizing profit and minimizing risk.

In natural systems, and specifically organic systems, one needs to think in terms of “Balance” and harmony.

Maximizing growth is equated with obesity and cancer in organic systems.

Minimizing growth is equated with starvation and Collapse in organic systems.

However, in the context of sustainability, it is useful to consider a minimum sustainable density.

For now we choose to identify minimum sustainable density as the Autonomobile Sweet Spot although at some point the whole Autonomobile-exclusive house of cards will Collapse.


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  1. Ray Hyde Avatar

    Is that gross, or net acreage?

  2. Ray Hyde Avatar

    “One of the lessons of urban history is that when cities become too large and unpleasant, people try to escape them.”

    “We need to green our cities, far more imaginatively and on a far larger scale than currently envisaged.”

    “…a city that satisfies more of an individual’s needs to connect with nature will generate fewer second homes, less travel and traffic congestion, less of the resource use that results from constant population upheaval and disruption to infrastructure. “

    “So, what kind of design should we plan to nowday cities? A compact city as Howard designed a hundred years ago? Indeed, I think we need to do the opposite – to “undesign” cities, make them looser, welcome nature back in.”!E0D2E56212BF668C!787.entry

    How does this idea conform to your ideas concerning density and planning?

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