Chuck Purvis asked the question last week. Here is a list of our current plan. WE WANT
YOUR INPUT on the additional geographic levels. Some are 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 can post to the
listserv (ctpp-news(a)chrispy.net)
Here are the basic levels, but not the detailed information.
State
State-County
State-County-MCD (in selected states)
State-County-Place (2,500+)
State-Place (2,500+)
State-County-Combined Zone -- Combined zones are limited to combinations of tracts 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.
State-County-Tract-Block Group*
State-County-TAZ *
*The smallest unit of tabulated geography can be TAZ, Block Group, or Tract
Possible levels (if there is any interest)
For the 3 geographic levels listed below, we would like to know if there is any 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 boundary.
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 Bureau could
include these for RESIDENCE and WORKPLACE tables.
1. CTPP Region: This will be defined by each MPO. It will be one or more whole 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.