The Bureau of Transportation Statistics Priorities for the Future (1997) / Chapter Skim
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3 FOCUSING ON DATA QUALITY
3 FOCUSING ON DATA QUALITY
Pages 31-63
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From page 31... ...
The 1991 Intermodal Surface Transportation Efficiency Act (ISTEA) recognized the need for a statistical agency with a broad mandate to provide leadership for transportation data improvement by stipulating that BTS issue guidelines to ensure that the information from the U.S.
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From page 32... ...
The remainder of this chapter first discusses staffing requirements for BTS and then considers priority activities for BTS in the data quality area. Such activities include the development of quality standards for USDOT and improvements in the documentation of available data, both to assist data users and to provide the basis for continuing evaluation and improvement of transportation data systems.
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From page 34... ...
We did not ourselves conduct a review of the quality of transportation data programs, and hence we cannot say whether they have serious data quality problems. However, no set of data is without error, and every data program has quality problems to a greater or lesser degree.
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From page 35... ...
. Such a program will require not only that BTS address data programs that it operates directly, but also that it work collaboratively with statistical units in other modal administrations in USDOT and with other data providers to ensure a focus on the quality of transportation data.
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From page 36... ...
At present, BTSis a small agency; it lacks the depth and breadth of statistical and methodological expertise on its staff to coordinate a comprehensive program for USDOT of documenting, evaluating, and improving the department's data or, more generally, to provide statistical advice to other units.4 A key element in BTS's future evolution as a statistical agency will be its ability to develop the necessary capabilities on its staff. BTS's progress in this regard will become even more important to the extent that budget pressures on the other modal administrations in USDOT constrain their ability to maintain statistical and analytical expertise in their agencies.
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From page 37... ...
Needed areas of skill include statistical sampling, statistical design, cognitive foundations of survey measurement, advanced data collection methods, editing, imputation for missing data, and statistical estimation from complex sample surveys. At present, BTS's statistical staff capabilities are augmented by Census Bureau staff who work on the Commodity Flow Survey and the American Travel Survey.
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From page 38... ...
The BTS statistical staff would take the lead in working with statistical units in the other USDOT modal administrations to develop standards and priorities for data documentation, evaluation, and improvement of the department's data systems. The BTS statistical staff would also provide technical assistance to the other modal administrations as appropriate.
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From page 39... ...
When BTS is larger, it could consider occasionally detailing one or two people to another statistical unit within USDOT, to another federal statistical agency, or to another organization with statistical expertise, as a way for staff to gain valuable experiences and insights. Similarly, BTS could sponsor staff from other USDOT modal administrations or other federal statistical agencies to work at BTS.
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From page 40... ...
to reduce the authority of any other officer of the Department of Transportation to collect and disseminate data independently." However, our view is that this provision does not contradict the mandate for BTS to develop guidelines for data quality for USDOT in collaboration with statistical units in the other modal administrations. Indeed, we urge that the reauthorization of BTS strengthen its role by requiring it to develop data quality standards, consistent with good statistical practice, that are binding throughout USDOT and available for use by transportation agencies outside USDOT and for reference by the public (see recommendation 3 at the end of the chapter)
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From page 41... ...
Those reports have regularly included a section on the state of transportation statistics, but those sections have been general in nature and do not meet the need we see for reporting improvements on specific quality dimensions for specific transportation data programs or sets of related programs. We discuss the role of the Transportation Statistics Annual Reports in providing needed time series indicators and analyses of transportation trends in Chapter 4, where we suggest that there may be more cost-effective ways of providing these kinds of information than the current prescribed format.
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From page 42... ...
For example, for a household or business survey, a statistical agency may set a standard for a minimally acceptable final response rate from the sampled units, such as 75 or 85 percent, and set aside funds to be used for additional follow-up efforts if the initial data collection efforts fall short of obtaining the specified standard.7 Many statistical agencies have minimum publication standards for the reporting of survey estimates: for example, differences across time or population groups will not be reported in summaries of findings if they fall below specified criteria 6Striving for comparability of key concepts and definitions must be undertaken carefully. In some instances, comparability may not be feasible, except by moving to a least common denominator in which importance nuances are blurred or lost.
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From page 43... ...
(Agencies with this type of standard may or may not also establish minimum acceptable quality Some data programs in USDOT represent samples of administrative records for which statistical sampling considerations apply (e.g., the Carload Waybill sample of information provided by Class I freight railroads for a 1 percent sample of rail waybills, which the Federal Railroad Administration uses to analyze traffic patterns and competitiveness issues; the General Estimates System of the National Highway Traffic Safety Administration, which contains information on a sample of policereported traffic crashes; and the Passenger Origin and Destination Survey of the Office of Airline Information in BTS, which contains information from a 10 percent sample of airline tickets)
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From page 44... ...
Written standards can thus serve both to define an internal spirit in this direction and to define the image of the organization to the larger world. Established statistical agencies vary in the types of standards they have developed and in how they achieve compliance with quality standards (see U.S.
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From page 45... ...
At the same time that BTS is developing its own quality standards, it should be working with other statistical units in USDOT as recommended earlier to develop quality standards for the department as a whole. It will clearly be important to work on standardizing definitions and other aspects of data systems for the department, to the extent feasible and appropriate, that can facilitate cross-modal and system-wide analyses of transportation data sets on a comparable basis.
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From page 46... ...
In order to carry out a strengthened mandate to establish binding data quality standards for USDOT (whether publication standards, consistent definitions, or minimum acceptable quality standards) , BTS in collaboration with the department-wide standards committee recommended earlier will need to develop explicit written standards in most instances.
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From page 47... ...
It has also not yet begun to evaluate available data systematically nor to lay out a program of improvement of key transportation data sets. The result is that users now have access to a large volume of information of varying quality with no roadmap to assist them in understanding the limitations and appropriate uses of particular data sets.
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From page 48... ...
Developing such materials will require that BTS staff themselves become expert users of the CFS data, which, in turn, is one of the best ways for a statistical agency to evaluate the quality of a data set and to determine needed improvements in both data and documentation. Assuming that future rounds of the CFS continue to be cosponsored with the Census Bureau, BTS should become an active partner in planning and reviewing the accompanying informational materials.
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From page 49... ...
. BTS should also encourage staff of statistical units in other USDOT modal administrations to publish methodological papers about their own data systems in the journal and should investigate the possibility of joint articles with staff from other statistical agencies on issues of mutual interest.
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From page 50... ...
National Transportation Statistics Compendium The annual National Transportation Statistics (NTS) reports are intended to serve the same reference function for transportation as the annual Statistical Abstract of the United States does for a wide range of subject areas that is, to bring together a large number of data series in a single, regularly updated volume.
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From page 51... ...
The Statistical Abstract of the United States, which includes many topics besides transportation, provides information on sampling and nonsampling errors for major data sources that is not found in the NTS reports, along with more extensive table notes for transportation data series than are found in the NTS reports. As an example, the Statistical Abstract of the United States (Bureau of the Census, 1996b:614)
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From page 52... ...
Web Site The BTS web site (see Figure 2-1) is a vast cornucopia of material, including: descriptions of BTS data products and services; data from selected reports and files from BTS and other sources; reports, reference documents, and many other publications from a wide range of sources (in the National Transportation Library portion of the site see Figure 2-2~; and links to other agencies, including the USDOT modal administrations, other federal agencies, and private organizations with some connection to the transportation field.
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From page 53... ...
i3That the full NTS reports are not yet available on the BTS web site is surprising, given that the site provides the complete text of statistical reports from other modal administrations (e.g., 1995 Highway Statistics from the Federal Highway Administration)
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From page 54... ...
Traffic Safety Data: PARS and GES Transportation Data Sampler-3 Transportation in the United States: A Review Transportation Safety Transportation Statistics Annual Report (TSAR) 1994 Transportation Statistics Annual Report (TSAR)
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From page 55... ...
The Traffic Safety Data set was developed by the Bureau of Transportation Statistics and the National Highway Traffic Safety Administration's (NHTSA) National Center for Statistics and Analysis (NCSA)
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From page 56... ...
In an effort to communicate directly with this high-risk segment of the driving public, Pennsylvania's Center for Highway Safety Program collaborated with the South Central Pennsylvania Highway Safety Program to establish special safe driving promotions at local speedways throughout 13 counties in Central Pennsylvania. 64% ts91395h.html Summary: 100% Platinum Pacesetter Safety Belt Honor Roll MARYLAND PROBLEM IDENTIFICATION During the past several years, Maryland law enforcement agencies received extensive state and national recognition for their promotion of safety belt use.
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From page 57... ...
1 7,732 312 Accident Rate Per 100,000 Hours Flown Total 0.19 0.00 Fatal 0.01 0.00 Accident Rate Per 100,000 Departures Total 0.30 0.00 Fatal 0.01 0.00 1 Exposure data estimate source: Research and Special Programs Administration and FAA Source: National Transportation Safety ... 62% tab9-3.txt Summary: TABLE 9.3 AIRLINES (Air Carriers Operating under 14 CFR 121)
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From page 58... ...
At present, the archive contains 11 listings, of which some are descriptions of data products rather than data (see Figure 3-3~. To help the user locate additional data and information, the BTS site provides links to the web sites of the other USDOT modal administrations (these links are to the main administrations and not to their statistical units)
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From page 59... ...
; the documentation that is provided in these publications about data collection methods and data quality varies according to the practices of the originating agencies. At this stage of its development, it may not be feasible for BTS to standardize the documentation for all of the data sets it makes accessible on its web site from the other modal administrations (or other sources)
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From page 60... ...
BTS should plan and begin to implement systematic programs of evaluation and improvement of key transportation data sets. BTS Surveys As a first priority, BTS should review the evaluations it has completed or has under way for the two major intermodal surveys that it sponsors to determine what further evaluations are needed and what the evaluation results imply for appropriate use of the data and for future design decisions.
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From page 61... ...
However, the subnational estimates it provides could be difficult to interpret because the information for each year's area sample would necessarily pertain to transportation by residents or shippers within the specified areas and not also to movements of people or goods into those areas from nonsample areas. Careful consideration of transportation analysis needs and of the costs of alternative designs will be required to determine an optimal strategy for how
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From page 62... ...
Such a role is in keeping with the establishment of BTS in the 1991 ISTEA as the statistical agency with a broad mandate to improve transportation data within the department. BTS can begin immediately to work with the other USDOT modal administrations to identify additional information on data quality and limitations that should be added to the descriptions on the BTS web site and in BTS compendia and reference publications.
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From page 63... ...
The reauthorization should also: · require the secretary of transportation to appoint a departmental standards committee, chaired by the BTS director and with representatives from the USDOT statistical units, to work with BTS in developing department-wide data quality standards and · require BTS to prepare every 2 years a report to the Congress that identifies improvements achieved in data quality by BTS and the statistical units in the other USDOT modal administrations and in the provision of information about quality to data users. Data Documentation (4)
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