Mr. Burrell has the history and the process right. Alan
----- Original Message -----
From: "Don Burrell" <DBURRELL(a)oki.org>
To: "'ed christopher'" <edc(a)berwyned.com>om>; "'ctpp-news
Sent: Thursday, November 08, 2001 5:19 PM
Subject: RE: [CTPP] Re: Geographic coverage, C2SS & ACS
Why do we have tracts?
Yes, ed, your memory is correct about the Bureau "creating" census tracts,
but they relied on the recommendations of the local "Census Tract
Committees" of data users to provide the boundaries. This is still the
process for the decennial review of the tracts. (I worked on coordinating
this review in the Cincinnati CMSA for 1990 and 2000.)
But, we have census tracts mainly as geographically stable over time
statistical analytical areas. Municipalities, enumeration districts and
zip-codes, on the other hand, keep moving their boundaries. This is also
reason that we can split census tracts in growing
areas, but that they
to nest to the same parent tract of the preceding
census, and that the ID
tract numbers are changed with suffixes so that it is obvious that the
represented by the tract-split numbers aren't the
My experience with TAZ's, again with the Cincinnati MPO, is that you
wouldn't want to go there. We have just overhauled our tazs for 2000. Most
changes are splits, but some aren't. They don't match tracts. And many are
small enough to represent blocks in the CBD and major traffic generators
(shopping centers, employers) with little or no resident population to
Census tracts are good.
Don Burrell, Senior Planner
Bicycle / Pedestrian Coordinator (formerly data person)
OKI Regional Council of Governments
801-B West Eighth St. Suite 400
Cincinnati, OH 45203-1607
513-621-9325 - fax
<A bicycle is an instrument for playing the road>
From: ed christopher [mailto:firstname.lastname@example.org]
Sent: Thursday, November 08, 2001 4:37 PM
To: 'ctpp-news maillist'
Subject: Re: [CTPP] Re: Geographic coverage, C2SS & ACS
since patty raised the issue of tracts, i have often wondered why do we
tracts? why don't we
have a zonal system in urban areas that is created by the public data
users--something like TAZs. in
many areas the TAZs are developed by a collection agencies with planning
if memory serves me tracts were historically a creation of the census
which is a data
collector. TAZs are a product of regional planning organizations (which
happen to have
transportation responsibilities) which are data users.
Patty Becker wrote:
Again, please feel free to post this to the list
serve if you wish.
My clear understanding is that "small area" means tract. I don't think
anyone thinks the 60 month data will be good enough for block groups.
If TAZs are tract equivalent, then the data should be as good as for
tracts. For heavy attractor TAZs which are split below tract level, the
transportation community has to negotiate with the bureau for a special
> to deliver all TAZs. The data should support the tab
> adequately, Meanwhile, of course, someone is going to have to be
> responsible (MPO by MPO and state by state) for keeping the geocoding
> up to date!
> No one knows whether these 60 month data are going to "feel right."
> time will tell. But in any event the CTPP users
will have data
> to that for all users who use tracts. Meanwhile,
we still have all
Congress, etc. etc.
Midwest Resource Center
Federal Highway Administration
19900 Governors Drive
Olympia Fields, Illinois 60461