|Federal Highway Administration Metropolitan Planning Division and Office of Highway Information Mgt Bureau of Transportation Statistics Federal Transit Administration In cooperation with the TRB Subcommittee on Census Data for Transportation Planning||
Message from the Chair
The Uses of the 1990 CTPP Data
Beginning in February 1999, DOT will implement TAZ-UP. At this time, a copy of (1) the TAZ-UP delineation software, (2) the TAZ-UP manual, (3) "TIGER98" and (4) ArcView 3.1 (for those who said they needed it!) will be mailed to all participating MPO agencies. The MPO will have six months from the time they receive the TAZ-UP materials to delineate their 2000 TAZs and return them to Census Geography to incorporate into TIGER/Line. For those MPOs who are requesting 2000 TAZ submittals using a GIS software other than ArcView 3.1, details will be delivered soon regarding Census Geography Division export specifications.
Beginning in early 2000, "TIGER99" will be available for release, which will include the MPO delineated 2000 TAZ boundaries.
If you would like to talk about how your agency has used CTTP data in the past or your plans for the CTPP 2000, please submit a brief article to Tom Mank and he will try to include it in the April CTPP 2000 Status Report.
Census data on journey-to-work was first collected in the 1960 Census, but it wasnít until the 1970 Census that journey-to-work data was available at a fine-grained geographic level. Transpor-tation planners of the Ď70s realized that standard census products werenít sufficient to meet our data needs, so the first "urban transportation pac-kages" (UTP) were created from 1970 Census data files. This program has evolved into the Census Transportation Planning Package (CTPP) as we know it today. The CTPP is the special decennial census product created by and for transportation planners.
So, how is CTPP data used by MPOs (see the sidebar "Use of Census Data by MPO Planners")? When will we get Year 2000 Census data? What kind of "master analysis plan" do I need to do a thorough job in analyzing, summarizing, comparing, critiquing, and disseminating results from the 2000 Census? What is the "American Community Survey"? These are some of the important questions that MPO and State DOT management needs to ask themselves (and their staff) in preparing for the onslaught of new data from the Year 2000 Census.
Letís say youíre the executive director for an MPO, and on April 1, 2003 the Census Bureau sends you a compact disk. Something from some guy named Phil and something about CTPP. An hour later, a local journalist from the city desk asks you about changes in commute patterns to the central city in your region. And how do they get to work? And why is this happening? Like most executive directors, you will pass the CD on to your most wise and trusted data analyst, and order him or her to get the answers off of the darn computer, please & pronto!
My recommendations to MPO and/or State DOT management and staff are
Appoint or anoint someone as chief census contact, NOW! This person will work with the Census Bureau and USDOT on various census activities.
Participate in the TAZ-UP project. MPOs and State DOTs will have an
opportunity to define travel analysis zone boundaries for the Year 2000
Census, for inclusion in the Census Bureauís TIGER files, and in future
CTPP products. This is a critical project for the near term (early 1999).
Review the Literature. Itís not too early to figure out whoís done what with census data in the past. New MPO staff, or MPO staff recently assigned census analysis duties, should obtain a copy of the Transportation Research Boardís Conference Proceedings #13: Decennial Census Data for Transportation Planning: Case Studies and Strategies for 2000. Volume 2: Case Studies. Papers include analyses by staff of large MPOs such as Philadelphia, San Francisco, Detroit and Chicago; and smaller MPOs such as Albany, New York; Rutland County, Vermont; San Luis Obispo, California; and Gainesville, Florida. To get a copy of this study, contact Tom Mank by phone at 202-366-4087 or e-mail him.
Network. Join the internet-based CTPP-NEWS electronic mailing list. Either "lurk" on these mailing lists, or join in on the discussions. Attend the TRB annual meeting and participate in the activities of the Subcommittee on Census Data for Transportation Planning.
Educate. Even though the CTPP is a special census product created by and for transportation planners, it makes good sense to educate others on the usefulness of CTPP data. Potential audiences may include your state data center, your regional data center, your regional census offices (yes, the regional Census Bureau offices are quite interested in this thing called the CTPP!), and local planning and business communities.
Uses of Census Data by MPO Planners
|Travel Model Validation. Transportation planners calibrate and validate home-based work trip generation, trip distribution and mode choice models against census-based "observed" home-based work trips.||Transit Operations Analyses. Transit operators use the CTPP and census products in transit route planning, captive rider analyses, performance analyses, rail station market area analyses, and latent demand analyses.|
|Trend Analysis. Census data in general and the CTPP data in particular is used by transportation planners to show past trends as a basis for forecasting current and future conditions. Trend data is well appreciated and generally well understood by policy-makers, the public and the media.||Land Use & Demographic Model Validation. Planners use the CTPP to calibrate and validate land use allocation models (e.g., DRAM/EMPAL, PLUM), as well as demographic models (e.g., workers in household, persons in household, vehicles in household models).|
|Microsimulation. Transportation planners are using PUMS data for microsimulation models, including developing synthetic population estimates for input to very disaggregate "next generation" travel behavior models.||Policy Planning Analyses. Regional planners use census and CTPP data for policy-level planning analyses, including jobs/housing balance studies, community quality of life measures, and transportation equity and accessibility analyses.|
|Demographic Benchmarks. The decennial census is the benchmark for all socio-economic forecasts produced at the local, regional, state and national level.||Sample Survey Weighting and Expansion. Transportation planners use the CTPP and standard census products to weight and expand regional household travel surveys.|
|Economic Development Analyses. The CTPP is not only used by MPOs and State DOTS, it is used by housing market analysts, labor force analysts, and economic development agencies. What is unique about the CTPP is the data on workers at place-of-work, and worker flow data between home-and-work, not available from other standard census products.||Small Area Employment Estimation. Land use planners use the CTPP as an independent database for estimating small area (travel analysis zone-level) employment by employment industry sector.|
|Bridge Studies. Weíre not talking Brooklyn Bridge. By "bridge studies" we mean the transition from our old friend the traditional census "long form" to our new buddy, the "American Community Survey" (ACS). About 37 counties will be a part of the ACS project in the 1999 to 2001 time period. Bridge studies will assist planners in comparing the results from the traditional long form and the ACS, and transitioning from traditional once-a-decade long form data to continuous-through-the-decade ACS data. If your MPO or State has one of these 37 counties, then you may be interested in participating in these bridge studies.|
Someday Your Data Will Come! Census data analysts will need to anticipate the release of several standard census products (PL 94-171, STF1A, STF3A, PUMS) as well as the pricing implications for the internet-based American FactFinder. Analysts will want to "line up their ducks" by preparing old (1960-1990) census data so that Year 2000 census can be "dropped right in." Analysts should learn about "embargo dates" so that the MPO gets the data at the same time as the local media! Analysts need to figure out the "spin control" to analyze the " whatís happening and why?" of census trends on the same day as the media gets the numbers. Have some fun-and-games with your media: have 1960 to 1990 trend data for your region, and ask your media to guess what the Year 2000 will show.
Be Alert! The highly political issue about sampling for reducing the census undercount is now at the US Supreme Court level. The local census data analyst should pay close attention to these issues and be prepared to brief local policy-makers on possible implications. Local advocacy may be in the cards, depending on the nature of the politics of your region. Good sources for keeping up-to-date on the census scene are the web addresses on page 1 of this document.
The most intensive use of the 1970 UTPP was at the University of Illinois at Chicago where nearly a dozen studies funded by the U.S. DOT and the local agencies were completed. One product was to allocate non-geocodable work places to the local geography. The Service Area Identification Methodology model developed with this dataset was used for vanpool, dial-a-ride, carpool and other para-transit service planning based on analyzing the workers' home and work locations. Conceptually, the model has been re-applied, with some modifications for planning many of the current welfare-to-work initiatives.
Building upon this history, CATS was one of the 150 purchasers of the 1980 UTPP. Although the agency attempted a small-scale update of its 1970 travel survey in 1979, the 1980 UTPP data became the "recognized" database for producing regional travel data and statistics for small geographic areas. CATS staff developed a bulletin called Transportation Facts (T-Facts). T-Facts focused on travel flows, modes to work, travel corridors and other descriptive statistics relative to understanding travel behavior. Two of the most requested T-Facts focused on travel to Chicago's CBD and county level work trip flows for 1970 and 1980.
As the decade of the 80ís advanced so did CATS staff expertise with the use of the package. CATS staff prepared custom tabulations from the UTPP, with summaries of the daytime population (workers at work) and their commuting patterns by mode being the most popular. Travel time was also a highly sought after variable but it came from a fully loaded network and not directly from the UTPP. Clients included banks, loan institutions, prospective business entrepreneurs and relocating corporations. The 1980 UTPP was also used in support of CATS car and vanpooling planning efforts.
By 1990, a nationwide funding arrangement was put together by AASHTO and the CTPP package was born. The 1990 package was available to virtually every MPO and state. Early in the decade, CATS served as the primary distributor and technical assistance provider on the CTPP. Later, when BTS issued the CTPP on CD-ROM, CATS role in technical assistance diminished.
The 1990 CTPP was used by CATS and NIPC, all of the major transit agencies including the Regional Transportation Authority (RTA), Chicago Transit Authority (CTA), Metra (commuter rail) and Pace (suburban bus) and the academic and research communities. Given the diversity of users, the range of questions addressed is expansive. Also, due to the availability of the package, there likely were many other private users that received copies whose work with it went undetected.
CATS' use of the 1990 CTPP falls into four general areas: factoring and adjusting surveys; descriptive reporting; special studies; and model development. Before using the data CATS first checked it against other local data to assure its quality. CTPP employment in Chicago's Central Business district for various levels of geography was compared to other known sources of employment data. This comparison also looked at changes between 1980 and 1990. Not only did this provide a validity check on the CTPP, it also provided some insights into the employment changes that took place.
Factoring and Adjusting Surveys
The CTPP has proven to be an invaluable resource for factoring and adjusting other surveys. By collecting some identical variables in its 1990 Household Travel Survey as contained in the CTPP, CATS was able to factor, adjust and expand its survey to some known values. Admittedly, this could be done with other Census data products but not at the geographic level provided by the CTPP.
As with the 1980 UTPP, CATS undertook an aggressive program to summarize the 1990 CTPP. One-page statistical summaries of the transportation related variables were produced for census places in the metropolitan area, community areas in the city of Chicago and for each county in the state. One was produced for the place of residence and another for the place of work and bound into a series of reports. The data on the summaries was also converted to a spreadsheet format for importing into other software.
County-level work trip flow tables, mode to work summaries, trends over time and a variety of other data summaries were created and widely distributed through reports and the T-Facts series. CATS' goal was to get the data in the hands of the users so they could apply it in their own planning and research efforts.
There have been a few special studies undertaken that have used portions of the CTPP to support welfare to work questions, high speed rail analysis and corridor studies. CATS has also used the Indiana CTPP data to help define a zone system for inclusion in CATS planning efforts.
The CTPP and other Census products play an important role in CATS modeling and model development work. The use ranges from providing direct inputs for trip generation to producing work-trip flow and descriptive statistics to check the models' outputs.
Whenever anyone talks about the CTPP they cite the need for data at a small area geography for transportation planning. This is certainly true and so is the need for locally collected travel survey data. For CATS' trip generation both products are used. In somewhat oversimplified terms CATS uses its travel survey to produce trip rates but then assigns those rates based on a cross-classification scheme to households at a much finer level of geography made possible by the CTPP. The CTPP is also used as an adjunct to the auto ownership component of trip generation. In addition to trip generation, the CTPP also provides data to support the mode split process in the form of auto occupancy and median income. Finally, it is used as a good independent source of information on mode split, travel time and O-D information for validation and calibration purposes.
In 1995, an inventory of uses of the CTPP in transit planning, found eleven different applications. A few are listed below:
|Ten-district Transit Origin-Destination Flow Analysis (RTA). This compared relative changes between 1980 and 1990 in work trip flows between ten major districts to examine implications for service/facility improvements.||CBD Modal Market Shares by Work Trip Origin Zone (RTA). Analyzed 1980-90 shifts in market share by mode for CBD work trips originating in outlying zones to examine implications for service improvements.|
|Commuter Rail Station Area Market Shed Analysis (Metra). Analyzed population, household and employment in uniquely defined market sheds centered around each commuter rail station using 1980 and 1990 CTPP data as well as 2010 forecasts.||Rapid Rail Transit Corridor Market Analysis (CTA). Compared results of local onboard surveys against related census travel and demographic variables for spatially defined market sub-area. This was influential in defining further marketing and promotional strategies to increase ridership.|
|Non-CBD Work Trip Origins for Selected Suburban Work Centers (RTA). Examined distribution of home end and non-CBD work as an input to suburban transit feasibility analyses.||Urban Core Bus Route Profiles (CTA). Developed atlas of key travel and census variables for census tracts within a one-mile band straddling each of 125 bus routes in the CTA service area.|
|Suburban Bus Transit Marketing Plan (Pace). Analyzed changes in travel markets using flow, origin and work location data from 1980 and 1990 to identify implications for marketing and service improvements.||Commuter Rail Express Service Study (Metra). Looked at the distribution of 1990 and forecasted 2010 households along a commuter rail line to examine the potential for express service.|
RESEARCH AND ACADEMIC COMMUNITY
The CTPP has been used in two thorough studies of labor sheds in the Chicago area, both of which examined the 1980 and 1990 packages. It was used to produce weights for the CATS 1990 Household Travel Survey and to produce a procedure for estimating survey response rates. In smaller metropolitan areas around the state, it has been used to study inter-county work trips and to assist in developing new definitions for metropolitan areas. The CTPP has also been used by a not-for-profit organization to study target neighborhoods and the flow of workers in and out of these neighborhoods. At one university, work with CATS' household surveys and the 1970, 1980 and 1990 CTPPs is underway to relate changes in travel behavior to congestion and air quality. At another university, research with the 1980 and 1990 CTPP data to investigate the connection between location and employment growth was undertaken.
Overall the CTPP has become a well-used data set but, as Census products
go, only a relatively small, specialized audience knows about it.
However, its user audience is growing, as are its uses, as more and more
individuals become exposed to it and the product it improves. More
information detailing the use of the CTPP can be found at:
Also in 1999, BTS has proposed a program in coordination with the Census Bureau to improve the place-of-work geocoding of both the American Community Survey (aka continuous measurement) and CTPP 2000. As many know, if there has ever been a complaint about past CTPP's, it has usually been with the quality of place-of-work geocoding.
For all of this to come about, we need to make sure that the user community (i.e. anyone reading this!) stays informed, brings forth their concerns and, most of all, keeps others informed. Because the CTPP comes out only once every ten years, there is a large group of individuals who are always new to the data product. As a result, it is incumbent on all of us to make an extra effort to make sure that our newer users understand the data and its strengths, and are welcomed to the greater CTPP community.
Early in 1998 as the Subcommittee was being formed, I noted that one of the most important activities of the committee would be to provide for the flow of information about the CTPP. I am still committed to that goal and welcome new participants to take advantage of the electronic mail list. To join it is as easy as dropping me an email at: firstname.lastname@example.org.
I look forward to hearing from you in the new year.
Finally, those who are interested in keeping apprised of the CTPP 2000 activities are encouraged to join our electronic mailing list by sending an E-mail to: email@example.com with the words "subscribe ctpp-news" in the body of the message.
Chair, Subcommittee on Census Data for Transportation Planning
In the first place, the creation of the lists was very labor intensive and time consuming for many MPOs, and often required extensive administrative dealings with other agencies. The collection and processing of the lists was very labor intensive and time consuming for the Census Bureau too, as the files were received on various media and in many different formats. The Bureau had to obtain and process a number of other large reference files as well. The result was a complex, difficult to manage process.
For 2000, one of our first goals was to cut down on the total number of inputs to the process. We also felt it would be less difficult for the majority of MPOs to review a list that already existed, rather than create a list themselves as in the past. Toward this end, the Bureau has licensed a commercial business database for use in the 2000 census that covers the entire nation. The file is based on yellow pages, commercial white pages, and government blue pages phone directories. Unlike the Bureauís internal establishment list, which is census-confidential and not available to the public, the vendor who owns the leased file has agreed to an MPO review prior to Census using the file for place-of-work coding.
Another important issue for Census was the need to standardize the files coming in from the MPOs. We faced a similar issue in the 1990 census in regard to traffic analysis zone (TAZ) equivalency files. The problem was effectively addressed by Census distributing a personal-computer-based application program to the MPOs for the equivalency work that also created a standard output file for transmittal back to Census. It seemed reasonable to consider a comparable process for the 2000 employer files.
Our plan is to develop a GIS-based program, similar to the TAZ update program, for MPOs to review, correct, update, and extend the employer names and addresses in the commercial business database Census has leased.
Our intent is to create an application that will display on a TIGER/Line98 base the locations of employers successfully geocoded by Census. The application will allow the user to choose various ways to organize the review process: by number of employees, industry type, street name, ZIP code, etc. MPOs will be able to correct the information for businesses coded to the wrong location. They will also be able to add employers missing from the original file and delete firms no longer in business. Records for companies that Census was not able to geocode will be provided as well, and MPOs will have the capability to indicate their locations. The application will create a standard output file for transmittal back to Census.
As noted above, we envision the Local Review of Employer Files (LREF) occurring after the TAZ update program. However, if some MPOs see an advantage to overlapping the two processes, that may be possible. We think six months should be sufficient for an MPO to complete the review, and hope to be able to begin distribution of the application during May or June of 1999. Place-of-work coding is currently scheduled to begin in June of 2000 and some processing of the files will be required prior to this, so all employer files need to be returned to Census by January 2000 at the latest.
The details of the LREF program will be worked out in the next month or so. In the meantime, if you have comments or suggestions about the process, please call Phil Salopek at (301) 457-2454, or email them to him at firstname.lastname@example.org .
The Uses of the 1990 CTPP Data
|COMSIS Corporation. Transportation Planner's Handbook on Conversion Factors for the Use of Census Data, Publication No. FHWA-PD-96-030. Washington, DC: U.S. Dept. Of Transportation, [May 1996]||Transportation Research Board / National Research Council. Decennial Census Data for Transportation Planning: Case Studies and Strategies for 2000 - Volume 2 - Case Studies (Conference Proceedings 13), Publication No. ISBN 0-309-05970-4. Washington, DC: National Academy Press, |
|JHK & Associates. CTPP Handbook: An Instructional Guide to the 1990 Census Transportation Planning Package, Publication No. FHWA-PD-95-019. Washington, DC: U.S. Dept. Of Transportation, [February 1995]||Transportation Research Board / National Research Council. Proceedings of the National Conference on Decennial Census Data for Transportation Planning, Special Report 206. Washington, DC: Transportation Research Board / National Research Council, |
|JHK & Associates. Using 1990 Census Data to Support Transportation Planning and Policy Development - An Overview of the CTPP, Publication No. FHWA-PD-94-036. Washington, DC: U.S. Dept. Of Transportation, ||Transportation Research Board / National Research Council. Census Data and Urban Transportation Planning in the 1980s, Publication No. ISBN 0-309-03763-8. Washington, DC: Transportation Research Board / National Research Council, |
|Rossetti, Michael A. and Barbara S. Eversole. Journey-To-Work Trends in the United States and its Major Metropolitan Areas: 1960-1990, Publication No. FHWA-PL-94-012. Washington, DC: U.S. Dept. Of Transportation, ||Transportation Research Board / National Research Council. Information Needs to Support State and Local Transportation Decision Making into the 21st Century - (Conference Proceedings 14), Publication No. ISBN 0-309-06206-3. Washington, DC: National Academy Press, |
|Transportation Research Board / National Research Council. Decennial Census Data for Transportation Planning (Conference Proceedings 4), Publication No. ISBN 0-309-06055-9. Washington, DC: National Academy Press, ||Transportation Research Board / National Research. Advances in Transportation Data: 1997, Publication No. 1593. Washington, DC: National Academy Press, |
|Transportation Research Board / National Research Council. Decennial Census Data for Transportation Planning: Case Studies and Strategies for 2000 - Volume 1 (Conference Proceedings 13), Publication No. ISBN 0-309-05965-8. Washington, DC: National Academy Press, ||U.S. Dept. Of Transportation, Federal Highway Administration, Office of Policy and Office of Highway Information Management. Census Mapbook for Transportation Planning, Publication No. FHWA-PL-94-035. Washington, DC: U.S. Dept. Of Transportation, [December 1994]|
|Transportation Research Board / National Research Council. Transit Markets of the Future - The Challenge of Change, TCRP Project H-4B Washington, DC: Transportation Research Board / National Research Council, [February 1997]|
|"Surf's Up" Web Sites to Remember|
|Ed Christopher (Census Subcommittee Chair)
|Chuck Purvis (Urban Data Committee Chair)
|Ed Limoges (Census Subcommittee Secretary)
|Ron Tweedie (State Data Committee Chair)
Census Population Division (JTW questions)
Census Geography Division (for TAZ update questions)
|Tom Mank (2000 CTPP Status questions)
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