CTPP October 2006

ctpp@listserv.transportation.org

9 participants
15 discussions

by Murakami

Thanks Sam! I am interested in identifying systematic issues so that approaches to improve the overall quality of the data can be made. The recent discussions here, and on the lehd-ltd listserv have indicated a problem with School Districts and employment at individual schools. Glad to hear that Ohio has improved the ES-202 file to address this! I would like to know if there are other industry categories that have similar problems and what approaches to solving the problem have worked! The Multiple Worksite Report http://www.bls.gov/cew/cewmwr00.htm is a VOLUNTARY component of the QCEW/ES-202 program. There are 2 papers that may be of interest to you, linked to the FHWA Census page: http://www.fhwa.dot.gov/planning/census/lehd.htm Early research sponsored by the Bureau of Transportation Statistics examined data from Florida and Illinois. Results for Illinois found that the LED 2001 data had much fewer shares of people working in their county of residence compared to ACS. Please see the paper by Wende Mix presented at the 2005 TRB Conference on Census Data for Transportation Planning. This was attributed to over-assignment to headquarters locations. Another early paper which discussed multiple worksite businesses (also linked to the FHWA website) is by Julia Lane and Marc Roemer which indicates that there are 2 main issues: 1) a business is NOT identified as having multiple sites, and 2) even if the business is identified as having multiple sites, the list of those sites may be incomplete. Lastly, just as a reminder, the universe of the QCEW/ES-202 is different from Census or ACS household surveys. 1. QCEW does not include self-employed. LEHD program is exploring use of Census Business Register to add self-employed. In the Census 2000, about 10% of workers reported they were self-employed. 2. QCEW does not include military or federal government or postal workers. LEHD program is working with OPM to get federal employees included. 3. The coverage in the Agriculture & Mining sectors is not always complete depending on the state. 4. LEHD data count both jobs and workers. LEHD uses the "primary" job concept, i.e. the job with the highest earnings in each quarter, to assign a single workplace geography to a worker. I hope I am not sounding negative about LEHD! I think it has a lot of potential, after more data cleaning particularly with multiple site businesses at the front end, and integration with additional files. Elaine Murakami FHWA Office of Planning 206-220-4460 (in Seattle) ------------------------------------------------------------------------ - For those of you who didn't already know, the US Dept of Education maintains a national geo-codable database of K-12 schools at http://nces.ed.gov/ccd/ (go to Data Resources>Build A Table), where you can select a particular geographic area and fields include both school lat/lon and geocodable street address. I've used this site on several occasions to supplement ES202 data to geocode education employment throughout the state of Ohio and for multi-state metro areas. FYI, our ES202 employment agency in this state beginning in 2005 switched from coding all public K-12 employment to the district administrative offices to the individual schools. Sam Granato Ohio DOT, Office of Technical Services 1980 W. Broad Street, Columbus, OH 43223 Phone: 614-644-6796, Fax: 614-752-8646 "You can observe a lot just by watching." - Yogi Berra

17 years, 5 months

[CTPP] Software needs for TAZ definition and submission to CB for TIGER

by Murakami

The Census Bureau Geography Division has asked us to submit to them software requirements for TAZ definition by the end of Calendar Year 2006. We are working on the assumption that the CTPP pooled fund proposal will move forward through AASHTO's process. In 1998, FHWA contracted with Election Data Services to produce the TAZ-UP for software creating the 2000 TAZs used for CTPP 2000. TAZ-UP greatly simplified the ability to create and export TAZs to CB's TIGER files. The process was a big improvement over the paper-map-pencil drawings, which were used for the 1990 CTPP. For the 2010 Census, the CB has a contract with M-cubed and its subcontractor Caliper Corporation for software development to support the "Participant Statistical Areas Program" (PSAP). The PSAP includes the tract and block group definition process. The software being developed for this program can be modified to accommodate TAZ, SuperTAZ or any other geographic units that the transportation planning community would like to have added into TIGER. In our last regular CTPP meeting, we did discuss concepts of corridors and downtowns, but we think those would be best left as aggregates of TAZs that are handled later through a TAZ-equivalency process for CTPP, rather than adding them into TIGER. Below is a summary of our discussions from a meeting held on October 18, 2006. PLEASE LET US KNOW IF YOU THINK WE ARE MISSING SOMETHING IMPORTANT! Please send your remarks to nanda.srinivasan(a)dot.gov by November 10. Elaine Murakami FHWA Office of Planning 206-220-4460 Summary of Specifications The software should have the ability to create 3 levels of TAZs - one is a base TAZ which will be subsequently used to define two other larger size aggregations (optional by county). The base TAZ would be similar to the traditional "small area geography" TAZs in 2000. The software must provide ability to aggregate these TAZs to medium size (about 4,000 population) and larger size (about 20,000 population) aggregations (much like Block Groups being aggregated to Tracts, or Tracts aggregated to PUMAs), if desired by the MPO/State. The functional specifications include: 1. Load TIGER/Line 2008 or 2009 files in their native format, including TAZ, Tract, Block Group, Roads, water, and other polygon layers. 2. Display TIGER layers. 3. Import and display background layers: a. Import and display of other MPO or State owned data (shapefiles - points, lines, or polygons), as long as these files are in decimal degrees, NAD 83 projections. b. Import and display of aerial photography, as long as these files are in decimal degrees, NAD 83 projections. 4. Create or Devise Traffic Analysis Zone (TAZ) polygon features using screen digitizing starting from: a. 2000 TAZ geography, if defined, or else current Tracts or Block Groups. b. Using primary polygons in TIGER, if 2000 TAZs were not defined, or if the agency does not choose to use Tracts or Block Groups as starting point. c. The software should have the ability to aggregate polygons using a lassoing function (to zoom in or out), select polygons, or draw a line around (point-by-point) and add them to a TAZ. 5. TAZ Definition Guidelines: a. The software should prompt the user to create TAZs to cover the whole county without any discontiguity. Importantly, there should not be any sliver TAZs or duplicate TAZ numbering in any county. b. The maximum number of alphanumeric characters for TAZ might be set at 8. c. There may be cases where a TAZ boundary might require segment(s) to be added to TIGER. If there is a valid geography that does not show as a line segment (e.g.: a polygon bounded by a new road), the software must provide the ability to use the line segment as a TAZ boundary, and allow the user to print the view/map, annotate it, and submit it to electronically/via hardcopy to the Census Bureau. d. Counters: i. Count and display * 2000 total residential population (using 2000 block population counts). * 2000 resident worker population (workers by place of residence), and 2000 workers by place of work (using 2000TAZ/Block Group values) for each delineation of a TAZ. NOTE: CTPP Part 2 should be used for place of work counts. TAZ and Block Group counts are not available nationwide, although tract counts are available nationwide. * If the currently defined TAZ cuts across 2000 geography (TAZ/BG), then use proportion of TAZ by area in that BG/TAZ to estimate resident/worker counts. Because this task might be difficult, a separate cost estimate should be requested from the software developer. ii. Count and display the sum of resident workers, and workers by place of work to aid to determine the size of the TAZ. 6. Final Checks: Once TAZ definition is complete, and before export, the software must check for items 6a through 6e, and flag the items on a list. Export should be allowed only if all the following items are flagged. If any of these items are not satisfied, the software should loop the user through each entry. a. Completeness b. Contiguity c. Uniqueness: Ensure no duplicate TAZ numbers anywhere in a county. d. Check for polygon closure for each TAZ. e. Distinguish whether the user wants the TAZ boundary to move with a tract/BG boundary (since the tract boundaries will be draft at that time), or if the user wants the TAZ boundary to be locked and not move with a tract/BG boundary. 7. Export output: Upon completion of the TAZ definition and after completion of final checks (Step 6), the software should provide ability to: a. Export the file to the requirements of the Census Bureau, Geography Division. b. Export the final TAZ shapefile copy for MPO/State use. 8. (Optional by County) Aggregations of TAZs. Once basic TAZs are developed, the software must allow the ability to aggregate these TAZs into two other transportation geographies - A medium sized TAZ (Med TAZ), and a large TAZ (Lg TAZ). a. Use final TAZ shapefile as starting point to develop medium size (Med TAZ) or Large size (Lg TAZ) aggregations. b. The software should have the ability to aggregate polygons using a lassoing function (to zoom in or out), select TAZ polygons, or draw a line around (point-by-point) and add them to MZ or LZ polygons. c. Provide counters similar to item 5c to check the population/employment of these zones. d. Prior to completion and export, do final checks similar to item 6. e. Provide export outputs similar to step 8. B. Provide the final software on CD-ROM or through a web-based retrieval process. C. Provide a "Help" button to explain software features.

17 years, 5 months

[CTPP] Re: ctpp-news Digest, Vol 33, Issue 10

by Sam Granato

For those of you who didn't already know, the US Dept of Education maintains a national geo-codable database of K-12 schools at http://nces.ed.gov/ccd/ (go to Data Resources>Build A Table), where you can select a particular geographic area and fields include both school lat/lon and geocodable street address. I've used this site on several occasions to supplement ES202 data to geocode education employment throughout the state of Ohio and for multi-state metro areas. FYI, our ES202 employment agency in this state beginning in 2005 switched from coding all public K-12 employment to the district administrative offices to the individual schools. Sam Granato Ohio DOT, Office of Technical Services 1980 W. Broad Street, Columbus, OH 43223 Phone: 614-644-6796, Fax: 614-752-8646 "You can observe a lot just by watching." - Yogi Berra Dear CTPP listserv: As some of you are aware, the Census Bureau has been working with Department of Labor QCEW (formerly known as ES-202) files, combined with federal administrative records, to synthesize home-to-work flow tabulations for small geography. The first phase which used QCEW for 2002 and 2003 included 12 states: CA, CO, FL, ID, IL, MN, MO, NC, OR, PA, VA and WA. Cross-state commuting was addressed ONLY for MO and IL in a test. In the last 10 months, Ed Christopher and I have held several teleconferences to work together with State DOTs and State Employment Departments to work out data sharing agreements, and to discuss the possibility of improving feedback mechanisms to improve the quality of the data. In the past, when State Employment Departments shared their data, when a State DOT or MPO made "corrections" to the file for using the data in a transportation application, there was no mechanism to recommend that someone in the Employment Department check the original data to make a correction. Most often, this has to do with establishments with multiple sites, where all the employment is coded to one location, rather than multiple locations. Most recently, on the lehd-ltd listserv (see below on how to sign up), there was a discussion about the lack of specific school locations and the assignment of school employment to a district or school board headquarters office location. But, no dataset is perfect. This link includes some materials from a transportation perspective on the LEHD http://www.fhwa.dot.gov/planning/census/lehd.htm Because the LEHD holds promise as a source for annual home-to-work flow tabulation for small geography, we would like to encourage you to examine the data, and to discuss your findings with the transportation data community. We will have a session at the TRB Transportation Planning Application conference in Daytona Beach in May 2007 to discuss some of the work done so far. The Census Bureau now has a new project in place covering 43 states and QCEW data for 2004. In this project, cross-state commuting will be addressed for all states, and the 2002 and 2003 data will be updated to account for cross-state commuting. To sign-up for the lehd-ltd listserv, http://lists.census.gov/mailman/listinfo/lehd-ltd/ Please read Jeremy Wu's email below regarding the Cornell site with access to data from Oregon and Texas, after you register as a user. If my email has any mistakes, I hope that Jeremy will send corrections! Elaine Murakami FHWA Office of Planning 206-220-4460 -----Original Message----- From: lehd-ltd-admin(a)lists.census.gov [mailto:lehd-ltd-admin(a)lists.census.gov] On Behalf Of jeremy.s.wu(a)census.gov Sent: Tuesday, October 24, 2006 10:30 AM To: lehd-ltd(a)lists.census.gov Subject: [lehd-ltd] On The Map Data Available from Cornell University Oregon and Texas data for On The Map are now available through the Census Bureau's partnership with the Cornell Institute for Social and Economic Research (CISER) at Cornell University. On The Map went live on the Internet in February, and it has grown to 16 states with Georgia to be added in November. On The Map is the first synthetic data product released by the Census Bureau. Ten (10) distinct copies, known as implicates, are produced; one of them is used for the current implementation of On The Map . The CISER site provides an Internet-accessible computing environment dedicated to the exploration and development of synthetic data. Data for the state of Washington are being loaded at this time, and data for other states will be added over time, pending the interests of the states and the users. See attached update for more details or visit http://lehd.dsd.census.gov. (See attached file: OnTheMap Update 061019.pdf)

17 years, 6 months

[CTPP] LEHD On The Map Data Available from Cornell University

by Murakami

Dear CTPP listserv: As some of you are aware, the Census Bureau has been working with Department of Labor QCEW (formerly known as ES-202) files, combined with federal administrative records, to synthesize home-to-work flow tabulations for small geography. The first phase which used QCEW for 2002 and 2003 included 12 states: CA, CO, FL, ID, IL, MN, MO, NC, OR, PA, VA and WA. Cross-state commuting was addressed ONLY for MO and IL in a test. In the last 10 months, Ed Christopher and I have held several teleconferences to work together with State DOTs and State Employment Departments to work out data sharing agreements, and to discuss the possibility of improving feedback mechanisms to improve the quality of the data. In the past, when State Employment Departments shared their data, when a State DOT or MPO made "corrections" to the file for using the data in a transportation application, there was no mechanism to recommend that someone in the Employment Department check the original data to make a correction. Most often, this has to do with establishments with multiple sites, where all the employment is coded to one location, rather than multiple locations. Most recently, on the lehd-ltd listserv (see below on how to sign up), there was a discussion about the lack of specific school locations and the assignment of school employment to a district or school board headquarters office location. But, no dataset is perfect. This link includes some materials from a transportation perspective on the LEHD http://www.fhwa.dot.gov/planning/census/lehd.htm Because the LEHD holds promise as a source for annual home-to-work flow tabulation for small geography, we would like to encourage you to examine the data, and to discuss your findings with the transportation data community. We will have a session at the TRB Transportation Planning Application conference in Daytona Beach in May 2007 to discuss some of the work done so far. The Census Bureau now has a new project in place covering 43 states and QCEW data for 2004. In this project, cross-state commuting will be addressed for all states, and the 2002 and 2003 data will be updated to account for cross-state commuting. To sign-up for the lehd-ltd listserv, http://lists.census.gov/mailman/listinfo/lehd-ltd/ Please read Jeremy Wu's email below regarding the Cornell site with access to data from Oregon and Texas, after you register as a user. If my email has any mistakes, I hope that Jeremy will send corrections! Elaine Murakami FHWA Office of Planning 206-220-4460 -----Original Message----- From: lehd-ltd-admin(a)lists.census.gov [mailto:lehd-ltd-admin(a)lists.census.gov] On Behalf Of jeremy.s.wu(a)census.gov Sent: Tuesday, October 24, 2006 10:30 AM To: lehd-ltd(a)lists.census.gov Subject: [lehd-ltd] On The Map Data Available from Cornell University Oregon and Texas data for On The Map are now available through the Census Bureau's partnership with the Cornell Institute for Social and Economic Research (CISER) at Cornell University. On The Map went live on the Internet in February, and it has grown to 16 states with Georgia to be added in November. On The Map is the first synthetic data product released by the Census Bureau. Ten (10) distinct copies, known as implicates, are produced; one of them is used for the current implementation of On The Map . The CISER site provides an Internet-accessible computing environment dedicated to the exploration and development of synthetic data. Data for the state of Washington are being loaded at this time, and data for other states will be added over time, pending the interests of the states and the users. See attached update for more details or visit http://lehd.dsd.census.gov. (See attached file: OnTheMap Update 061019.pdf)

17 years, 6 months

[CTPP] Seminar Friday 10/27--Alan Pisarski on Communting

by ed christopher

Portland State University has a speaker series that is webcast. This Friday, noted author of Commuting in America (Volumes 1, 2 and 3) will be speaking. Alan's talk is entitled "The End of Commuting". Below is the information on how to log into the webcast or view the presentation at a later date. -------------------------------------- Date: Sun, 22 Oct 2006 11:18:04 -0700 From: Jennifer Dill Subject: Alan Pisarski Presentation These weekly seminars are webcast live. Use this link: www.cts.pdx.edu/seminars.htm Archives are posted a few days after the seminar. Speaker: Alan E. Pisarski Topic: The End of Commuting When: Friday, October 27, 2006, 12:00-1:30 pm (West Coast Time) Where: 204 Urban Center (www.pdx.edu/map.html) >Portland State University [link to event calendar >http://www.pdx.edu/cecs/events/11494/] >Center for Transportation Studies >Fall 2006 Transportation Seminar Series > > Archived seminars are now available for download! > Watch live video, see future scheduled seminars, and view archives: > www.cts.pdx.edu/seminars.htm > Email questions before or during the seminar: > Join our email list: www.cts.pdx.edu/email.htm > We look forward to your feedback. Thank you for your participation! --------------------------------- Jennifer Dill, Ph.D. Associate Professor Nohad A. Toulan School of Urban Studies and Planning (USP) Assistant Director, Center for Urban Studies Portland State University web site: http://web.pdx.edu/~jdill/ -- Ed Christopher Resource Center Planning Team Federal Highway Administration 19900 Governors Drive Olympia Fields, Illinois 60461 708-283-3534 (V) 708-574-8131 (cell) 708-283-3501 (F)

17 years, 6 months

[CTPP] ACS Proposal: Please comment by Oct 31st

by Chuck Purvis

I'm forwarding this recent message from the State Data Center Listserv. Chuck Purvis, MTC ********************************************************************************************************************************* >>> "Gage, Linda" <Linda.Gage(a)DOF.CA.GOV> 10/18/06 1:57 PM >>> The American Community Survey Office has posted a draft document describing a first-ever ACS summary file. All comments on the proposed approach described in this document must be sent via email no later than October 31. You can access the document at the following website: http://www.census.gov/acs/www/Products/users_guide/New_ACS_Summary_File_Spe… or, open the document at the bottom of this page: http://www.census.gov/acs/www/Products/users_guide/ Send any comments you have to Nick Spanos: nicholas.m.spanos(a)census.gov

17 years, 6 months

[CTPP] Nation's Population to Reach 300 Million on October 17th

by Ed Christopher

The "crystal ball in Times Square" is starting to drop! ---------------------------------------Nationan's Population to Reach 300 Million on Oct. 17 The U.S. Census Bureau today reported that the nation's population will reach the historic milestone of 300 million on Oct. 17 at about 7:46 a.m. (EDT). This comes almost 39 years after the 200 million mark was reached on Nov. 20, 1967. The estimate is based on the expectation that the United States will register one birth every seven seconds and one death every 13 seconds between now and Oct. 17, while net international migration is expected to add one person every 31 seconds. The result is an increase in the total population of one person every 11 seconds. http://www.census.gov/Press-Release/www/releases/archives/facts_for_feature… -- Ed Christopher 708-283-3534 (V) 708-574-8131 (cell) FHWA RC-TST-PLN 19900 Governors Dr Olympia Fields, IL 60461

17 years, 6 months

RE: [CTPP] CTPP Discussion Issues

by Zakaria

Hi Ken: I read your excellent analysis of Census 2000 Part III tract-level, county-level and state-level data sets. Your findings in the detailed spreadsheet for 12 counties in Texas are not unique to Texas. According to my evaluation of CTPP 2000 data for the Delaware Valley Region, the errors and completeness of census data stem mainly from rounding and disclosure threshold rules. The 2000 rounding and disclosure threshold rules resulted in 3 and 62 percent loss in the worker flow at the TAZ level, respectively. As you know, Table 3-06, which shows TAZ-to-TAZ worker flow by means of transportation to work became totally useless due to suppressed flow of workers. It is simply not possible to have synthesized Part III dataset at the TAZ level. We tried to develop a rational and convenient method to do this but we could not and thus were unable to use TAZ-to-TAZ data by means of transportation to work. Relaxation of the disclosure rules would not solve the problem. If the 2000 disclosure threshold were decreased from 3 unweighted workers to 1, the damage to the TAZ-to-TAZ worker flow would be significant still and the data would be useless. Based on this evaluation, I recommended last year not to use any disclosure threshold in the future. There was no disclosure threshold in the 1990 census and no one complained because of disclosure. Imputation, swapping and data rounding were used in the 1990 census to protect confidentiality and were sufficient to avoid disclosure. The "super TAZ" concept will not work in the northeast states, as well as Michigan, Wisconsin and Minnesota because these states have many small minor civil divisions, which consist of only one TAZ. Such small municipalities are interested in their own data. Also, data from "super TAZs" will not be useful for planning small transportation projects such as subway stations, highway interchanges, park and ride lots and local bus routes. Finally, I should state that the margin of error in the ACS tabulation will be larger than that found in Census 2000. The CB is saying now that the 2005 ACS will provide data for areas of 65,000 population and larger because the sample size was increased from that of 2004. Yet the 2005 ACS sample was not large enough to produce a table for all means of transportation to work and a table for workers by place of work and by industrial sector. This information was suppressed completely for Gloucester County, NJ (277,000 population), not 65,000 as promised by the CB. I know that Ed Christopher, Elaine Murakami, Jonette Kreideweis, Dave Clawson, Alan Pisarski, Nanda Srinivansan and others are aware of these CTPP issues. Hopefully, they will be able to resolve these problems and produce accurate CTPP data in the future. Thabet Zakaria Deputy Director, Technical Services Delaware Valley Regional Planning Commission Philadelphia, PA 19106 Phone: 215-238-2885 Email: tzakaria(a)dvrpc.org Fax: 215-592-9125 -----Original Message----- From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces(a)chrispy.net] On Behalf Of Ken Cervenka Sent: Tuesday, October 03, 2006 2:17 PM To: ctpp-news maillist Subject: RE: [CTPP] CTPP Discussion Issues Ed, Thanks for the additional info. The issues raised in the draft email I was working on relate to what you just said: 1) the idea of larger TAZs to limit disclosure problems; and 2) the idea of data synthesis to still get very small-area data. So my apologies for redundancy in addressing the same thing below, but in different words. ********************************************************************* Ed said at the end of his email to post questions/comments to the listserv, so... I do indeed hope AASHTO will approve the new CTPP Pooled Fund initiative. In spite of the difficulties "us MPOs" and other organizations have with uncertainties on the accuracy of Census products (and the ACS and CTPP 2000 comparisons people have been making are pointing out some important issues), and the impacts of disclosure rules applied to journey-to-work tables, the "long form" questions are nevertheless still important to the transportation planning process. As others before me have said (I recall Alan Pisarski giving a speech or two or three on this topic), the word "data" is not particularly glamorous to people outside the profession (and oftentimes rather boring to those within the profession), but yet represents the foundation to an informed (and democratic) decision-making process. So with those sincere accolades on the underlying importance of CTPP data--and hopes for AASHTO pooled funding--stated, now on to the technical issues. The current disclosure rules have been a major hindrance to "good" small-area transportation planning in which we want more than simply place-of-residence and place-of-work information: now I understand why the Census Bureau must always retain procedures that maintain confidentiality of individuals, but I wonder if there isn't more to be checked and confirmed, just to be sure that the "rules" in place are not being too restrictive. The impacts of the restrictions have been discussed many times before, but can be easily seen by working with the Census 2000 Part III tract-level, county-level, and state-level datasets available from: http://www.transtats.bts.gov (note: when you are at this location, just type in CTPP 2000 Part III in the "search this site" box to get to the appropriate downloading page). The attached spreadsheet shows some statistics for 10 different states, in which I summarized the Tract-to-Tract data in the State, for selected variables. Since not everyone's email is set up to receive attachments, here is the gist of what's shown on the spreadsheet: -- Question T301C1 represents total workers, which for these 10 states is 56,157,132 workers. -- Question T302C1_1 represents all workers residing in households that are definable by their "vehicles available in household" and seven "Means of Transportation" aggregated categories; the 10-state total is 55,643,556 workers, which is equal to 99.1% of the total workers (I presume the very minor loss in workers is due to the "residing in households" definition). -- Question T305C1 represents all workers residing in households that are definable by a household income category; the 10-state total is 65.7% of the total workers. -- Question T306C1 represents all workers residing in households that are definable by one of the 17 "Means of Transportation" detailed categories; the 10-state total is 66.4% of the total workers. Of equal significance are the variations of "completeness" for each of these 10 selected states, e.g., for Question T306C1 there is a range of 56.0% for New York to 79.8% for Oregon. When confronted with these "missing data" issues, I suspect some planners simply factor up the available trip table so it appears to represent the full universe--but even a cursory examination of county-level Part III trip tables versus "Part III tract-level aggregations to county" trip tables will show that the missing data is not equally represented across all categories. For example, consider the 17 "Means of Transportation" data for Dallas County: the tract-level aggregations represent 60% of the reported county-level total for drive alone trips; 80% of the total for walk trips; and 100% of the total for work-at-home trips. So if someone used a simple factoring process across all modes in the tract-level datasets to reach the full universe, the end result is that the actual number of drive alone trips would be significantly under-represented and the number of walk trips and work-at-home trips would be significantly over-represented in the factored tract-to-tract data. [Note: if anyone is interested, I have a detailed spreadsheet that shows these issues for 12 counties in Texas--but it is a rather messy spreadsheet that has not been thoroughly checked, so I don't want to forward to people unless they ask me via private email, and promise not to forward to a listserv]. Since most TAZs (at least as defined by the MPOs) are generally a LOT smaller than Census Tracts, the TAZ-to-TAZ trip tables from the CTPP 2000 effort wind up having even greater amounts of missing data for the income-related and "detailed means of transportation" categories. Which brings up two possibilities for future improvement (assuming there will be Part III datasets in the future at anything other than a County or PUMA level): 1. I wonder if there might be opportunities to someday have two sets of TAZ-to-TAZ files: one dataset would have the same "missing records" limitations we currently see (and agonize about), and the other dataset would be based on a process that uses some of the held-back information to "synthesize" the missing data to develop a fully-complete TAZ-to-TAZ table. Now independent researchers can already use various "Iterative Proportional Fitting" or similar imputation procedures to deal with missing data issues, but I am concerned that their techniques will not be as good as what the Census Bureau staff could do, since the CB staff would have access to more of the underlying raw data that would (or at least could/should) result in a "better" synthesis process. Now I can understand the cost implications and potential confusions of two sets of "official" TAZ-to-TAZ data, but this would give us end-user planners the greatest number of choices for making decisions about future land use and capacity changes. Plus, by making the "missing records" tables available, this would still give agencies an opportunity to conduct (at their own expense) their own imputation process that could then be compared against the CB's synthesized tables. 2. If it is simply not possible to have a synthesized Part III dataset at the TAZ level--and there is not much hope for any significant relaxation of the disclosure rules--then maybe we need to pay great attention to the "Super TAZ" concept, in which each TAZ is carefully defined so that it is "just large enough" to reduce the more serious confidentiality issues, while still being useful for planning. An example would be a typical CBD: this is MUCH smaller than a County or PUMA, but is often composed of many existing TAZs and Census Tracts. So instead of having a CBD represented by 25 TAZs, maybe it could be divided into just four or five TAZs--or even just one TAZ, if that's what it takes to keep the understandable confidentiality issues from over-taking our desires for a more democratic decision-making process that is based on understanding the world we live in. Ken Cervenka North Central Texas COG (Dallas-Fort Worth MPO) Kcervenka(a)nctcog.org ************************************************* -----Original Message----- From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces(a)chrispy.net] On Behalf Of ed christopher Sent: Tuesday, October 03, 2006 12:35 PM Cc: ctpp-news maillist Subject: Re: [CTPP] CTPP Discussion Issues Ken--the short answer is yes; Part 1, part 2 and Part 3 (flow data). With that said there will be some caveats and of course of lots of issues to be discussed, debated, researched and decided upon. In hearing from users and those active on the AASHTO SCOP Data Working Group people have been very clear that they want small area TAZ to TAZ flow data. Under the proposed pooled-fund, that would happen but certain concessions would have to be made to accommodate the Census Bureau's Disclosure Review Board concerns. One very practical notion on the table is to have a larger geography (call it a super TAZ for now) where we would have all our data with no suppression or other disclosure rules. From that we would extend a more traditional data package for the smallest zones (traditional TAZs) that would likely be synthesized. Some spot research is going on in this vein and the proposed pooled-fund calls for more as well as an NCHRP 8-36 proposal that we are hopeful will get funded. For now before we get too far a field I think it is critical to see that the pooled-fund comes to fruition. Ken Cervenka wrote: > Ed (or anybody) > > Could you please confirm that when you talk about TAZ data, you are > referring to not simply Place-of-Residence (Part I) and Place-of-Work > (Part II) summaries at the TAZ level, but the possibility for TAZ-to-TAZ > (Part III) datasets? If there is still hope for future TAZ-to-TAZ (or > super-TAZ to super-TAZ) dataset deliveries, I have lots to say on the > subject, that I am willing to put out on this listserv. > Ken C. > > -----Original Message----- > From: ctpp-news-bounces(a)chrispy.net > [mailto:ctpp-news-bounces(a)chrispy.net] On Behalf Of ed christopher > Sent: Monday, October 02, 2006 10:19 AM > To: ctpp-news maillist > Subject: [CTPP] CTPP Discussion Issues > > During the past few months I have received several questions regarding > the need for small area, Traffic Analysis Zone (TAZ), data from the > American Community Survey (ACS) so I thought I would provide an update. > > GENERAL UPDATE ON CTPP > > There are two groups that are working on census data needs for the > transportation community. > > First there is the long-standing CTPP Working Group that meets monthly > and has been responsible for the content of the 1980, 1990 and 2000 data > packages. Although the precise membership of this working group has > changed over time it has generally been made up of US DOT staff, Census > Bureau (CB) staff, Dave Clawson from AASHTO, and members of > Transportation Research Board (TRB) committees. The work of the CTPP > Working Group tends to focus on the highly technical aspects of the > data. Since 1997, this group has met at least once a month and has been > chaired by Elaine Murakami of FHWA. > > Working in concert with the CTPP Working Group, the AASHTO Standing > Committee on Planning (SCOP) last August (2005) initiated a broader > based Committee called the SCOP Census Work Group. Jonette Kreideweis > of the Minnesota DOT chairs this group. Its main focus has been on > issues that transportation planners need to know to use the ACS and it > has been instrumental in recognizing that a "family" of new data > products will be needed. In June the Work Group proposed a pooled-fund > project that includes data products, research, training, and technical > support. The pooled-fund is currently before SCOP and I hope that it > will be approved by AASHTO in October. The pooled-fund builds upon the > experience gained from the 1990 and 2000 pooled-fund projects and > details on it can be found on the TRB Subcommittee on Census Data > website at http://trbcensus.com/SCOP/ > > TAZ DEFINITION for ACS > > 1. Will MPOs and State DOTs be asked to submit new TAZs? > > Assuming that a new CTPP pooled-fund is approved by AASHTO, there will > be an opportunity to define new TAZs for CTPP data products. Questions > to be answered revolve around how many different TAZ systems should > there be, the cost for developing those systems and the mechanical > process for submitting them. To help define TAZs, discussions with the > CB's Geography Division are underway. > > 2. How will new TAZs be submitted to the Census Bureau (CB) and added > to TIGER? > > The CB has a contract with M-cubed and its subcontract Caliper > Corporation for software development to support the "Participant > Statistical Areas Program" (PSAP). The PSAP includes the tract and > block group definition process. The software being developed for this > program can be modified to accommodate TAZ, SuperTAZ or any other > geographic units that the transportation planning community would like > to have. As a result, it makes sense to have tract, block group, and > the TAZ definition efforts be a coordinated process. Of course the > development of any TAZs are premised on and would be paid for by the > pooled-fund. > > 3. When will the Census Bureau (CB) use the new TAZ definitions to > tabulate ACS data for CTPP? > > Since the CB PSAP to define track and block groups is focused on the > 2010 regular census, tabulations of ACS data issued in 2010 and after > would follow the new geographies. Any earlier products would use > existing 2000 geography. For example, the pooled-fund calls for > small-area tabulations from ACS data using a required 5-year period -- > 2005, '06, '07, '08 and '09. The data would not be released until > 2010-2011 and we have been assured that it would follow 2010 geography. > However, for our first 3-year product (2005, '06 and '07), we have to > use 2000 geographic units and meet the 20,000 population threshold per > zone. > > 4. What is the history of TAZ definition for CTPP? > > For the 1980 and 1990 data tabulations TAZs were restricted to 6 > characters and only one set of TAZs could be defined per region. The > data assigned to these TAZs represented an equivalency process where > MPOs were asked to let the CB know which blocks to assign to which TAZ. > Blocks could not be split and the TAZs really became an aggregation of > blocks and block groups. > > In 2000, a major improvement was made where the TAZs were defined early > and placed in the CB TIGER file. With the TAZs in TIGER the CB was then > able to put the actual data for the area the TAZ represented in the > predetermined TAZs. For the first time the "urban" TAZs became a unique > tabulation geography and not just an aggregation of Census geographical > units. While this new process was adopted for TAZs the equivalency > process remained for those areas that crated state-level TAZs. This was > due to size limitation of the TIGER record and other technical > processing issues. > > 5. WHAT are some items to consider? > > As we look toward the future and ACS related transportation data > products, further TIGER improvements are on the horizon. Inside the CB > the Geography Division is undergoing a major overhaul of its TIGER file > data base. Conceptually, TIGER is moving to something akin to a > relational data base and space limitations are a thing of the past. Not > only can we consider adding more characters to the TAZ field, we can > even talk about having different TAZ zone structures. Assuming the > AASHTO pooled-fund is approved, one of the first tasks will be to focus > on defining TAZs for inclusion into the new TIGER system. As a result, > we need to focus on what we want in terms of TAZs. > > Other items that are nearing the horizon concern the detail data tables > to be included in the various products. The pooled-fund is calling for > a one, three and five year transportation data product. However, before > we work on the specific details of the product design the pooled-fund > must first be approved and funded. > > As Chair of the TRB Urban Data Committee, the sponsoring committee of > the Census Data Subcommittee, I hope to see this list serve used as a > forum to feed these discussions. Currently we have over 550 subscribers > to this list, most who are the active census data users in their MPOs, > states, consulting firms and universities. > > Finally, if you have a question about any of this, please post it to the > list serve. We are at a critical time in terms of getting the > information out to our various users. So please share your comments, > questions and experiences. > > -- > Ed Christopher > Resource Center Planning Team > Federal Highway Administration > 19900 Governors Drive > Olympia Fields, Illinois 60461 > 708-283-3534 (V) 708-574-8131 (cell) > 708-283-3501 (F) >

17 years, 6 months

[CTPP] 2005 Transportation Profiles now posted on AASHTO webpage

by Murakami

Dear Everyone: We have created a limited set of profile sheets: National, States, a few large cities, and several Metropolitan Areas. The profiles include data from 1990 Census, 2000 Census, and the 2005 American Community Survey. http://ctpp.transportation.org/2005.htm PLEASE READ THE "NOTES" which has more information about "GQ: group quarters" "MOE: Margin of Error," and geographic comparison issues. The Census Bureau advices data users NOT to make direct comparisons between the ACS and decennial Census results because of changes in survey methods. However, one of the main uses of the newly released 2005 ACS is to examine trends from 2000. If your area was included in the sample of counties (about one-third of counties) in the 2000 ACS C2SS, we recommend that you include both 2000 Census and C2SS results when you analyze changes over time for RESIDENCE GEOGRAPHY. You will see in the "highlights" documents attached that we have included two bar charts using this approach. These pages use the 2005 ACS data released on August 29. We will be working on another set of profile sheets using the 2005 ACS data released on October 3. Elaine Murakami on behalf of the CTPP Team

17 years, 6 months

[CTPP] Calculating margins of error for derived estimates for ACS 2005

by Nanda.Srinivasan＠dot.gov

All- In the last few weeks, we have received questions on how to calculate margins of error (MOE) when you add, or subtract, or divide ACS 2005 data. The Census Bureau has some instructions for applying statistical testing to ACS Data posted at http://www.census.gov/acs/www/Products/users_guide/ACS_2005_Statistical_Tes…. Using these instructions, I prepared an MS Excel template for calculating MOE for additions, subtractions, proportions, or percents (please see attached MOE.xls). I am assuming 90% CI for my calculations. There are three worksheets (one for additions/subtractions, one for proportions, and one for percents). <<MOE.xls>> Hope you find these useful. Thanks Nanda Srinivasan 202-366-5021

17 years, 6 months

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CTPP October 2006