Why are we here Today?
To see first hand
how the TAZ/TAD
development
software works
Introduction to CTPP TAZs and TADs
What is CTPP
TAZs and TADs
Things to think about
Resources
What is the CTPP?
Census Transportation Planning
Products (CTPP) Program
The CTPP is an umbrella program of Census
related data products, custom tabulations,
training, technical assistance, and research for
the transportation community
Designed and paid for by transportation
planners for transportation planners
Why are Custom Tabulations so important?
Summarize data by
Place of Residence
Place of Work
Flows between Home and Work
Unique Universes (e.g. workers in HHs)
Custom Geography (Local TAZs)
Traffic Analysis Zones - defined by the local
transportation data user for the local
transportation data user
Sometime in 2013 New Product is due out
New
XXXXXXXXX Sometime in 2013
Geography
NO data will be suppressed
What is a TAZ/TAD?
● Custom Geography for
CTPP data tabulations
●Defined by MPOs and
State DOTS
● Developed in Spring/
Summer 2011
● Funded under CTPP
Program
● GIS equivalency process
built from Census Blocks
TAZ
Traffic Analysis
Zone
TAD
Traffic Analysis
District
Traditional
Size
20,000
population
What is an equivalency process?
Take the map at the
right and using the
states boundaries make
9 contiguous regions
It’s the same for TAZs
Blocks
cluster into
TAZs
TAZs/TADs Building Blocks
● 2010 Census Blocks
will make up TAZs
● TAZs will make up
TADs
● TADs can cross
Counties and States
● TADs can be built
from TAZs, Block
Groups or Tracts
http://www.fhwa.dot.gov/ctpp/acsdataprod.htm
The Schedule
Nov/Dec 2010 - Agencies verified contact names
Feb 2011 - Web-based training (2-25 and 2-28)
March through April 2011 - Online delivery of
software and Census 2010 data and geographic files
(Rolling basis)
3- Months to delineate TAZ/TADs
2010 TIGER files
http://www.census.gov/geo/www/tiger/tgrshp2010/tgrshp2010.html
June through July 2011 - Files returned to CB
Geography
TAZs/TADs Inserted into TIGER data base
TAZ Size
CB recommends
~600 persons
corresponds to the minimum
threshold for 2010 Census
Block Groups
Threshold is guideline not a requirement
TAZs may be defined with fewer than 600
residents or workers
Data reliability and availability improves as
population size increases
Bigger is Better
Why the hang-up on TAZ size
● ACS is a small sample
● Smaller areas have
lager MOES
● Statistical Collapsing
● Confidentiality and
Disclosure rules
Big Zones make happy data
Important concept to follow
When is a TAZ
Not a TAZ?
When it is a C-TAZ
Important Concept
TAZs and TADS for Census ACS data do not
have to be the same as the TAZs used in your
travel forecasting models
Think of these as
Census TAZs or (CTAZs)
Census TADs or (CTADs)
Travel Forecasting Zones as
Planning Zones or Planning Units
Large Zones are Better for ACS Data
Why are TADs so important?
NE Illinois (2009 3-year ACS)
● Higher quality data
● Less chance for
disclosure proofing
● More real data
● Potential 3-year data
coverage w/No Swiss
Cheese
5-year Geography and Flows
● Asymmetrical
Flows
● Small Areas
defined by MPOs in
MPO areas and
States Elsewhere
● Tracts are
Defaults for Small
Areas
● Default TADs
under discussion
TADs as CBDs, Special Districts, etc
The Software
Using the Census Bureau
MAF/TIGER Partnership Software
Census Bureau Contract (CTPP
Paying for it)
Caliper is the contractor
Calling it the MTPS TAZ Element formally TAZ-UP
Download materials, software and files from Census
Bureau site.
16
Some TAZs resource materials
Florida Standard
Urban Transportation
Model Structure
White Paper on Recommended Approach
to Delineating TAZ
http://www.fsutmsonline.net/images/uploads/reports/
FDOT_TAZ_White_Paper.pdf
http://www.fsutmsonline.net/images/uploads/mtffiles/PPT_12_TAZ%20White%20Paper_NOV07_FINAL_CS_Keli_Wu.ppt
Important sizes / More on PSAP
How many Block Groups can be contained in a single Tract?
http://www.census.gov/geo/www/psap2010/bg_criteria.txt
http://www.census.gov/geo/www/psap2010/psap2010_main.html
Thank You
Ed Christopher
FHWA Resource Center
4749 Lincoln Mall Drive, Room 600
Matteson, IL 60443
708-283-3534
edc@EdTheFed.com