Wrapping up the CTPP

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Wrapping up the CTPP What you should know
Ed J. Christopher FHWA Resource Center near
Chicago 19900 Governors Drive Olympia Fields, IL
60461 708-283-3534 edc_at_edthefed.com
April 26, 2005
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Today
Run Through CTPP Cover Some CTPP/Census Data
Issues
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What is the CTPP?
The Census Transportation Planning Package is a
set of special tabulations from the long form of
the decennial census designed by transportation
planners for transportation planners
It summarizes the data
Flows between Home and Work
At Residence
At Workplace
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CTPP Main Products
Tabulations at Residence
Tabulations at Workplace
Flows between Home and Work
Part 1 Part 2 Part 3
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How is it packaged?
CTPP Access Tool
The CAT
ASCII Too
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When was it released?
Part 1 -- Residence Data (Done) BTS has Final
ASCII version on TranStats Final CAT Files
distributed to MPOs / states
Part 2Work Place Data (Done) Final ASCII on
BTS TranStats Final CAT _at_ BTS Bookstore
Part 3 Flow Data Final ASCII (Done) Coming
Soon!!!!!
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Where do I get the FREE CTPP ASCII Files?
http//www.transtats.bts.gov/
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Where do I get the FREE CTPP with Software?
https//www.bts.gov/pdc/
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Install New (Part 3) Viewer Software
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CTPP Data Issues
Rounding and Thresholds Workplace
Geocoding Worker Counts Top Coding
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Disclosure Review Board
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Example of Rounding
Mode to Work Circa 1990 For 2000 (ROUNDED)
Total 352 350 (not 355!)
Drive Alone 212 210
Carpool 46 45
Transit 59 60
Walk 33 35
Bike 2 4
True Total 354
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Pop Quiz!
Using the CTPP, 10 10 10 10 ?
a) 30 c) 35 e) 40 b) 45 d) 50 f) Any of
the Above
Here's a real life example using the CTPP Part 2
data. Let's say my boss asks as simple question
"How many transit commuters are at work in the
Bay Area?" Using the Part 2 data, I am able to
provide my boss 15 different answers! Chuck
Purvis, MTC
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Chicago CBD -CTPP 2000 Data
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Rounding Tips

1. Obtain your "regional control totals" from the
   most geographically aggregate summary levels
2. Avoid aggregating (summing together) your
   geographies
3. Avoid aggregating categories
4. Sum as few categories as possible
5. Adjust (de-round, un-round) as you see fit. SF3
   or PUMS can provide control totals to adjust the
   CTPP Part 1 data.
6. Develop a sense of humor.

So is it "close enough for government work?"
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Odd Modes
Linn County, Cedar Rapids Iowa
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Odd Modes
Linn County, Cedar Rapids Iowa
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Thresholds
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No record threshold
Must have 3 unweighted records
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DRB Impact on Part 3
Special Thanks to Chuck Purvis, MTC For this
Analysis
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Workplace Geocoding
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Workplace Geocoding
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Workplace Geocoding Issues
Automatic Geocoding (75) Standard
Allocation (25)
Industry Improvements m TIGER Improvements
(TAZ Definition) m Work-up Clean-up m
Extended allocation 10 (ala Lemoges)
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Workers at Work Counts vs. Other Employment
Sources
Total jobs are HIGHER than Census 2000 worker
counts while CTPP Part 3 is Lower yet!
(Rounding) CTPP uses NAICS, others may use
SIC Multi-site businesses and job types not
reported consistently Census 2000 employment
estimates vs CPS Extended Allocation for CTPP
small areas
http//www.trbcensus.com/articles/ctppworkers.pdf
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Top Coding of Travel Time
The top coding of travel time changed between
1990 and 2000. In 1990, the data field for
travel time was limited to 2 digits thereby
restricting travel time to a maximum of 99
minutes. In 2000, the field was 3 digits with a
top coding of 200 minutes.
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Top Coding
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When I get my CTPP data what should I do?
Examine the data for your area as soon as
possible Check its reasonableness Does it
make sense? Are people working where they
should be? Do the tables add up? Report all
data issues to Nanda Srinivasan, FHWA, (Phone
202-366-5021, email nanda.srinivasan_at_fhwa.dot.gov
)
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Stay Connected
http//www.dot.gov/ctpp http//www.TRBcensus.com 2
02-366-5000
Are You on the CTPP-News Listserve? Have You Seen
our Newsletter (the Status Report)?
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When Mining Your Census Data Keep us in Mind

• Want to
• Show Off Your Work?
• Gain National Exposure?
• Meet Other Data Users?
• Tour Washington DC?

Sound Exciting?
Let Us Know What You Have Done We Are Always
Interested
TRB Urban Data and Information Systems
Committee Ed Christopher-Chair (708-283-3534)
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Now lets head off to the races with our latest
CTPPs