TAZ/TAD delineation program
overview
Overview
• Traffic Analysis Zone (TAZ) and Traffic Analysis
District (TAD) delineation criteria and guidelines
– Why define them? What are they?
– Criteria and guidelines
– How the criteria and guidelines are built into rules and checks in
the MTPS
• High level process/flow of the TAZ delineation
program
• Schedule
2
TAZs and TADs
Why define them? What are they?
• Traffic Analysis Zones (TAZs):
– a basic spatial unit of analysis representing an area
containing similar kinds of land use and commuter travel
– 5-year CTPP data
• Traffic Analysis Districts:
– aggregates of similar TAZs
– 3-year CTPP data
3
Criteria & Guidelines
TAZ
TAD
Notes
Aggregates of…
2010 census blocks
2010 TAZs
Overlap
TAZs may not
overlap (one TAZ
assigned/ block)
TADs may not
overlap (one TAD
assigned / TAZ)
Nest within &
cover the entire
area of…
Counties
State DOT/ MPO
coverage
State DOT and MPO coverage is one
or more complete counties. TADs
may cross county boundaries.
Codes
Unique within
county
Unique within
State DOT/ MPO
coverage
TAZ and TAD codes are up to 8
characters, alphanumeric, and
padded with leading zeros
Minimum
thresholds
Resident or worker*
population > 600
suggested
Resident or
worker*
population >
20,000
Data reliability and availability
improves as resident and worker
population increases
* 2000 block-level worker estimates
were interpolated to 2010 block
boundaries.
4
Criteria & Guidelines
Aggregates of…
TAZ
TAD
2010 census blocks
2010 TAZs
Notes
5
Criteria & Guidelines
TAZ
TAD
TAZs may not
overlap (one TAZ
assigned/ block)
TADs may not
overlap (one TAD
assigned / TAZ)
Notes
Aggregates of…
Overlap
Interactively, one can only assign an area to one
TAZ or one TAD. Adding an area assigned to an
existing TAZ or TAD to a different TAZ or TAD will
remove it from the original TAZ/TAD.
6
Criteria & Guidelines
TAZ
TAD
Notes
Counties
State DOT/ MPO
coverage
State DOT and MPO coverage is one
or more complete counties. TADs
may cross county boundaries.
Aggregates of..
Overlap
Nest within &
cover the entire
area of…
Nest within:
• TAZ delineation - will not allow you to select geography in two
different counties when creating or editing a TAZ
• TAD delineation – will not allow you to delineate TADs outside
the county coverage (in setup file)
Cover area of:
7
Criteria & Guidelines
TAZ
TAD
Notes
Unique within
county
Unique within
State DOT/ MPO
coverage
TAZ and TAD codes are up to 8
characters, alphanumeric, and
padded with leading zeros
Aggregates of…
Overlap
Nests within …
Codes
8
Criteria & Guidelines
TAZ
TAD
Notes
Resident or worker*
population > 600
(suggested)
Resident or
worker*
population >
20,000
Data reliability and availability
improves as resident and worker
population increases
Aggregates of…
Overlap
Nests within …
Codes
Minimum
thresholds
* 2000 block-level worker estimates
were interpolated to 2010 block
boundaries.
9
Additional checks
• Contiguity
• Compactness
10
High level TAZ/TAD delineation
process/flow
1
2
Check the AASHTO
website spreadsheets
to confirm expected
county coverage for
2010 TAZ/TAD
delineation. Let us
know ASAP if not what
you expect.
Receive email from GEO
TAZ team with
customized setup file,
and instructions to call for
MTPS download
username/password.
Mid-March through
April
3
Open setup file and
confirm correct county
coverage in
“CoreCountyCoverage”
5
4
Call GEO TAZ Team
for MTPS download
username/password
Download the MTPS
software, partnership
shapefiles (counties
specified in setup files),
and user documentation
from Census Bureau’s
website, save to local
drive
6
Save setup file to the
same local drive folder
as the partnership
shapefiles (e.g.,
“TAZlayers”)
11
High Level TAZ/TAD delineation
process/flow (2)
Can divide work among
multiple staff members
prior to delineation (by
editing the setup file (for
dividing work on
complete counties or
administratively
assigning county –
parts)
a
Choose startup methods for
TAZs and/or TADs
- TAZs: 2000 TAZs, 2010
tracts, 2010 block groups,
scratch, BEFs
- TADs (no TAZs): 2010 tracts,
2010 block groups
- TADs (with TAZs): scratch
and BEFs
4
Run setup for the MTPS,
and Delineate TAZs and
TADs
b
c
Delineate TAZs
e
Run TAD verification
checks
d
Run TAZ
verification checks
Delineate TADs
f
“Report Changes” (i.e., create
output files)
12
High Level TAZ/TAD delineation
process/flow (3)
5
FTP output files to Census
Bureau, follow up with email
Within 90 days from receipt
of setup file email: mid-June
to early-July
6
Census Bureau will run verification
checks on submissions, and will contact
program participant with any problems
or issues that do not have clear fixes
13
TAZ/TAD Delineation Timeline
• February 25 & 28: Web-based TAZ
delineation software training
• March – April: Delineation materials available
starting in March
• June – July: Delineation submission returned
to Census Bureau within 90 days of
delineation material availability (i.e., receipt of
setup file email)
14
Questions?
GEO TAZ team: geo.taz.list@census.gov
301.763.1099
15