using 5-year acs for transportation planning applications
DESCRIPTION
Using 5-year ACS for Transportation Planning Applications. Elaine Murakami FHWA Office of Planning [email protected] 206-220-4460 (in Seattle). The journey to work is still relevant. About 20% of Person Miles of Travel (and 27% of VMT) is Commuting Labor force participation rate: - PowerPoint PPT PresentationTRANSCRIPT
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Using 5-year ACS for Transportation Planning Applications
Elaine MurakamiFHWA Office of Planning
[email protected] (in Seattle)
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The journey to work is still relevant
• About 20% of Person Miles of Travel (and 27% of VMT) is Commuting
• Labor force participation rate:– 74% men– 62% women
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To/from work
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Commuting is key factor in congestion
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Census Transportation Planning Products
• Nationwide, customized tabulation for the transportation community
• First completed in 1970 (not nationwide), with subsequent packages in 1980, 1990, and 2000.
• Previously used decennial long form, now using ACS.
• Includes home-to-work flow4
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CTPP: 3-year and 5-year
– Received 3-year (2006-2008) from CB, and AASHTO (Beyond 2020) working to post on web
• Travel demand model calibration and validation• Analysis of transit major investments
– 5-year (2006-2010) due in 2012• Use of Census 2010 results to adjust weights n
the Population Controls• Requires implementation of new disclosure
avoidance (“masking”) techniques.
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Methods to protect individual confidentiality already in place with
ACS records
• Small sample• Data switching• Imputation
– High for income (13%)– High for place of work (20+%)
• Rounding for custom/special tabulations
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Census Bureau Disclosure Review Board: Rules for the CTPP 5-year tab
• Cell Means and aggregates require 3 unweighted records
• For Pt 3 (flow), 3 unweighted records for each table, each cell, with the exception of the 1-way MOT table.
• 3 unweighted records for the marginals in any cross-tabulation with MOT.
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:How many ACS records per tract or TAZ after 5
years of ACS data accumulation?
Census Tract TAZ (assume 5/tract)
Unweighted hhlds
120 24
Unweighted workers
150 30
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RESULT of this number of unweighted records with the DRB rules LOTS OF SUPPRESSSION
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What tables should be in the CTPP?
• Reduce the # of variables cross-tabbed with variable “Means of Transportation”– Reduced from 17 to 5 for the 3-year list.– Keep the reduced list of 5 cross-tabs
• Collapse the categories – reduce the total # of cells in each table.
• Use data synthesis methods (now using term “masking”)
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NCHRP 08-79: “Producing Transportation Data Products from the
ACS that Comply With Disclosure Rules NCHRP is funded by State DOTs SP&R• Project schedule: Jan 2010-July 2011
– Final report due in July 2011– Need results to be applied to 2006-2010 ACS for the
5-year CTPP (delivery in summer 2012)
• Westat, Tom Krenzke, PI
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NCHRP 08-79 (1)
Task 1: Review several approaches, including deterministic as well as random error applied to microdata records.
Task 2: Select 3 microdata approaches to test, and separated the CTPP tables into 2 sets:
A: those without DRB thresholds, and
B: those with DRB thresholds
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NCHRP 08-79 (2)
• Task 3: Develop and evaluate the 3 approaches to mask the underlying microdata
• 4 test sites: Atlanta, Iowa, Madison, St. Louis• 2 amounts: Full, Partial replacement
• Task 4: Develop data utility and disclosure risk measures– Compare perturbed and “true” ACS with travel model
outputs– Discussions with CB’s Disclosure Review Board
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NCHRP 08-79 (3)What is a credible method?
• Must be implementable at the CB • Schedule: Validate best approach Jan 2011.
– Must pass the DRB approval– SAS code which can be modified by CB ACSO staff– Computer processing time
• Interative processes must converge quickly• Bayesian approaches must not “run forever”
• Results must make sense to transportation analysts– Preserve the descriptive qualities– Should not result in erroneous diagnosis for validating
home-based work trips in travel demand forecasting models.
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Alternatives to ACS (and other household surveys) for transportation
planning?
• Societal changes in privacy and information access
• Survey response rates continue to decline– Response bias: Young, African American,
Hispanic, low-income
• Look for voluntary approaches (opt-in)
• Greater use of administrative records (LEHD OTM)
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Alternatives–Digital Footprinting
• Smartphones + GPS
• Mobile Millenium (UC)– Nokia, AT&T
• Bluetooth tracking
• RFID, including toll tags
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10111 10112 10113 10114 10115 10116 10117 10118 10119 10120 10121 1012210111 -- 6707 1068 560 120 137 250 187 174 117 143 10710112 6885 -- 1324 747 197 169 175 277 112 120 259 12110113 872 1067 -- 1228 357 176 53 388 29 130 510 9810114 401 531 1138 -- 1154 467 190 1387 99 403 1714 29110115 112 185 420 1626 -- 490 587 255 602 721 3449 26610116 72 95 154 596 397 -- 1599 1849 925 840 316 137510117 86 71 22 147 262 638 -- 165 1140 264 203 32910118 176 220 381 1553 95 1812 296 -- 102 357 127 49510119 93 60 28 212 606 1029 794 142 -- 807 443 74210120 38 54 111 456 623 1086 551 381 685 -- 470 45510121 115 201 524 2109 2764 333 377 159 340 443 -- 23010122 43 51 79 275 329 1526 480 477 706 686 237 --
O/D matrices using Bluetooth monitoring
10121
10115
ValuesRow Labels Sum of 15N21 Sum of 21N15
May7-May 180 2248-May 292 2159-May 289 16410-May 418 31411-May 399 35712-May 400 35013-May 395 34814-May 383 33815-May 273 19316-May 254 17917-May 166 82
Grand Total 3449 2764
F S S M T W R F S S M
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Balancing issues
ACS
Masked (Synthetic)
Requires 5 years accumulation
Link between demographics and behavior
Digital Footprinting
Anonymous
High currency
Highly detailed geog
New private sector partners
Lose link to demographics
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Thank you for your attention!Opinions are my own and do not necessarily reflect USDOT policies.
• Elaine Murakami– FHWA Office of Planning (Wash DC) – 206-220-4460– [email protected]
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