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Post by NCFC on Dec 12, 2012 16:23:13 GMT -7
The travel time to the edge of a city can be significantly shorter than the travel time to its center. Please explain why you chose to use the distance to the edge for the FAR methodology.
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Post by NCFC on Dec 12, 2012 16:25:14 GMT -7
[Answered by John Cromartie] There are two or three reasons to do that. One is, it doesn’t really change the results much whether you’re measuring from the center of a city versus the edge in terms of the influence of any given city. You would simply be adding a constant in terms of travel time from the edge to the center. Determining the center of a city is problematic, other than just choosing the geographic center of the urbanized area delineated by the census bureau. But the main substantive reasons are that cities are no longer uni-central. Especially the larger cities where this choice would make a significant difference – the cities larger than 1 million where the difference between the center and the edge is significant – those cities are evolving into cities dominated by suburban downtowns and edge cities. So you can’t really keep the assumption that the important services are in the city center.
The other reason is that the edges of all urbanized areas are defined the same way. The edges represent that point where population density shifts from rural population densities of 500 persons per square mile or below to above that threshold. Throughout the entire range of urbanized centers which go from total populations of 2500 up to the largest city, those edges are defined in the same way, whereas the center is very different and the internal structure of cities is very different. So that was the rationale in terms of choosing to measure from the edge.
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Post by NCFC on Dec 12, 2012 16:26:05 GMT -7
[Gary Hart] I’d just like to add that from a health care perspective, which I’m always looking at with these things, when you hit that edge, if I’m looking for hospitals and delivery systems that are higher-scale, hospitals are at the edge. Granted, in the middle of the city there may be something super, super high, but you’re going to start hitting high-level services and hospitals on the edges.
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Post by NCFC on Dec 12, 2012 16:26:35 GMT -7
[John Cromartie] With either choice, you have a measurement issue, in that either choice assumes you have uniform access once you’re inside an urbanized area. On the one hand, if you choose the edge, you’re assuming that services are automatically available as soon as you cross that edge. On the other hand, if you choose the center, you’re assuming that all the services are just at the center. So it is going to be a measurement issue adding some level of error in terms of measuring exactly how long it takes to get to a given service either way you choose.
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