I would be interested in adding a couple of additional summary levels:
Including MCD in the tract and block group summary levels would make it
easier to add a town name
to any reports generated from the tables. The CTPP Region and MPO Study Area
summary levels would
be useful - particularly for median income and travel time values, which are
not easily aggregated from
smaller geographic areas.
Chief Planner, GIS
Central Transportation Planning Staff
Boston Metropolitan Planning Organization
10 Park Plaza, Suite 2150
Boston, MA 02116-3968
Voice: (617) 973-8132
Fax: (617) 973-8855
----- Original Message -----
From: "Elaine Murakami" <Elaine.Murakami(a)igate.fhwa.dot.gov
Sent: Friday, March 08, 2002 4:16 PM
Subject: [CTPP] What Geographic Summary Levels will be included in CTPP?
Chuck Purvis asked the question last week. Here is a
list of our current
plan. WE WANT YOUR INPUT on the additional geographic levels.
only possible for RESIDENCE-based tables. Whether you want them or not,
please provide us with your feedback! Maybe since the GIS capabilities and
experience are so much better now than 10 years ago, no one needs to have
these levels included in the file, since you and your staff can aggregate
them from TAZ or Block groups directly.
You can reply either to me directly (elaine.murakami(a)fhwa.dot.gov) or you
to the listserv (ctpp-news(a)chrispy.net)
Here are the basic levels, but not the detailed information.
State-County-MCD (in selected states)
State-County-Combined Zone -- Combined zones are limited to combinations
or TAZs. They will be defined by the State DOTs (if they choose
to do so) and are intended to assist Statewide travel demand models, where
the small TAZs of an MPO are too detailed for Statewide applications.
State-County-Tract * Tracts will be included, even in
areas with TAZs.
*The smallest unit of tabulated geography can be TAZ, Block Group, or
Possible levels (if there is any interest)
For the 3 geographic levels listed below, we would like to know if there
interest in having these included for RESIDENCE tables. Because of
workplace geocoding difficulties, we cannot use these geographic levels for
WORKPLACE or FLOW tabulations.
1. ZCTA (ZipCode Tabulation Area) This is an approximation of a Zipcode
2. PUMA (Public Use Microdata Area) These are areas
with a minimum of
100,000 population based on tract or place boundaries.
3. Urbanized Area (areas with more than 50,000
population with the
required density level)
For the 2 geographic levels listed below, it is likely that the Census
include these for RESIDENCE and WORKPLACE tables.
1. CTPP Region: This will be defined by each MPO. It will be one or more
counties submitted by the MPO as constituting their CTPP region.
Totals for the sum of the counties included in the CTPP Region will be a
separate summary level for the RESIDENCE and WORKPLACE tables. The FLOW
tabulation will include the smallest unit of geography for each county. All
counties are not required to have the same unit, e.g. 3 counties may use
TAZ, and 1 county may use tracts. TAZs can be used only if they have been
defined in the TAZ-UP process.
2. MPO Study Area: This is a list of TAZs (by county) or tracts (by
county) to be
submitted by an MPO for which RESIDENCE AND WORKPLACE tables
can be prepared. Totals for the sum of these TAZs (or tracts) will be a
separate summary level for the RESIDENCE and WORKPLACE tables. This
special geography is provided as a convenience. An MPO planning area might
not include whole counties, but we required TAZs to be defined across an
entire county. By adding this summary level, a total that does not extend
to county boundaries can be easily found on the CTPP file.