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Chapter 6Dissemination of Information

Chapter 6
Dissemination of Information

Dissemination is the distribution of information to the public, in any medium or form, including press releases, reports, data files, or web products. These standards cover releasing information (Section 6.1) and ensuring the accuracy and interpretability of different types of BTS information products: tables, graphs, and maps (Section 6.2), text (Section 6.3), and micro data (Section 6.4). The standards also cover issues affecting all information products: data protection (Section 6.5), rounding (Section 6.6), and revisions (Section 6.7). Finally, the public documentation standard (Section 6.8) provides for the transparency and reproducibility of the information disseminated by BTS.

6.1 Releasing Information

Standard 6.1: Procedures for the release of information products to the public must receive predissemination reviews (disclosure, content matter, statistical and methodological) and must include provisions for ensuring fair access to all users.

Key Terms: information product, peer review, sensitive material

Guideline 6.1.1: Release Schedules

To provide fair access to the public, major information products should follow published release schedules.

  • Provide the schedule for the release of information products to the BTS public affairs office for release.
  • Protect information to be published against any unauthorized pre-release or disclosure in advance of the publication schedule.

Guideline 6.1.2: Ease of Accessibility and Understanding

Information products should be made accessible to the public.

  • All information products disseminated through the Internet should comply with the requirements for Section 508 of the Rehabilitation Act of 1973, as amended.
  • Codes, abbreviations, and acronyms should be used sparingly and defined in accordance with the BTS Guide to Style and Publishing Procedures. Provide definitions to the user in the product.
  • As appropriate, information products should also include definitions of any subject-matter-specific or otherwise technical terms.

Guideline 6.1.3: Formal Pre-Dissemination Review

All information products require pre-dissemination review to ensure compliance with OMB and DOT Information Quality Guidelines, and BTS standard procedures.

  • Before sending an information product outside the originating office for review, the product manager should:
    • Verify compliance with all applicable BTS standards and guidelines (BTS 2002, 2003, 2004, 2005),
    • Double-check facts,
    • Proofread text, and
    • Clearly mark the product as a draft for review only, and not for attribution or further distribution.
  • All information products require a confidentiality protection review (BTS 2004).
  • Verify calculations through an independent recalculation of a random selection of statistics in the information product.
  • Persons not directly involved in preparing the information product should proofread the text and verify that numbers in tables, graphs, maps, and text are consistent.
  • All information products require a subject-matter review by someone, preferably from within BTS, who is familiar with the topic area and with the techniques used. The information product may require a separate review of the statistical methodology.
  • If the topic may be of interest to another DOT organization, industry group, or others in general, ask formally for review by those deemed most interested.
  • Publication specialists should edit text products to ensure consistency and readability.
  • The appropriate office director should review and clear all information products before submitting the products to the Director or the Directors designee. The Director or designee will review the product and determine whether the product needs further review within the Research and Innovative Technology Administration (RITA) prior to final dissemination approval.
  • Information products to be posted on the web require review for compliance with BTS web guidelines. Each information product should be assigned to at least one of the program web pages.

Guideline 6.1.4: External Peer Review

If an external peer review process is used:

  • Select peer reviewers primarily on the basis of necessary technical expertise,
  • Any non-government peer reviewers paid by BTS must disclose to DOT any prior technical/policy positions they may have taken on the issues at hand and their sources of personal and institutional funding (private or public),
  • Conduct peer reviews in an open and rigorous manner, and
  • Consider all relevant technical comments, although outside reviews are not binding on BTS.

Guideline 6.1.5: Contact Information

All information products must include a contact reference to BTS customer service. As part of the dissemination process, inform the information service of new products and provide background information so that the information service staff can appropriately respond to, or forward, inquiries regarding the information product and its data sources.

Related Information

Bureau of Transportation Statistics (BTS). 2002. Section 508 Compliance Plan, Version 1.0. Washington, DC.

__________. 2003. BTS Guide to Style and Publishing Procedures. Washington, DC.

__________. 2004. Confidentiality Procedures Manual. Washington, DC.

__________. 2005. BTS Statistical Standards Manual. Washington, DC.

Office of Management and Budget (OMB). 2000. Electronic and Information Technology Accessibility Standards, Final Rule. Federal Register, Vol. 65, No. 246, pp. 80500-80528. Washington, DC. December 21.

__________. 2002. Guidelines for Ensuring and Maximizing the Quality, Objectivity, Utility, and Integrity of Information Disseminated by Federal Agencies. Federal Register, Vol. 67, No. 36, pp. 8452-8460. Washington, DC. February 22.

__________. 2005. Final Information Quality Bulletin for Peer Review, Final Bulletin. Federal Register, Vol. 70, No. 10, pp. 2664-2677. Washington, DC. January 14.

__________. 2005. Standards for Statistical Surveys (Proposed), Sections 6.1 (Review of Information Products) and 7.1 (Missing Data). Washington, DC. July 14.

U.S. Department of Transportation (DOT). 2002. The Department of Transportation Information Dissemination Quality Guidelines. Washington, DC. Available at as of January 19, 2005.

Approval Date: May 4, 2005

6.2 Tables, Graphs, and Maps

Standard 6.2: Tables, graphs, and maps in BTS information products must accurately and effectively convey the information intended.

Key Terms: external source, statistical map, weighted average

Guideline 6.2.1: Identifying Content and Sources

As far as possible, tables, graphs, and maps should be interpretable as stand-alone products.

  • Titles for tables, graphs, and maps should be clearly worded and identify the content. Include the timeframe and geographical limitations. The axis units may serve to identify the timeframe for graphs.
  • All tables, graphs, and maps must have a complete source note (BTS 2003b). Include information not immediately evident from the main body of the presentation, such as definition of codes, acronyms and special terms, and anything else that would not be obvious to the general reader.
    • Source references should be sufficiently detailed for a reader to identify the data used. Source notes in all products must give a full citation for the actual source from which the data were taken, even if that source merely collected data from other sources.
    • Since databases and documents may be updated, the as of date for the source should also be noted. Web links should include the URL and date accessed. Even a report featuring results entirely from one source should have the source note with each table, graph, or map, in case they are separated from the report.
  • When presenting estimates that are calculated using data from external sources, note each source and add a statement describing how the calculation was done. If the calculation is complex (e.g., a weighted average constructed from raw data and weights), include a description of the methods used or a reference to where they are described. Cite BTS as the source of the calculations, based on the external source.
  • Use footnotes to clarify data illustrations, tables, graphs, and maps regarding particular points, abbreviation symbols, and general notes.

Guideline 6.2.2: Consistency of Presentation

To facilitate comparability, be consistent in constructing tables, graphs, and maps within an information product that cover similar material and use similar units.

  • Tables, graphs, and maps within the same information product should use similar fonts, units, spacing, and line thicknesses. Symbols and codes should also be similar throughout an information product.
  • For comparability across BTS products, tables and graphs must comply with BTS style and formatting guidelines (BTS nd, 2003a, 2003b).

Guideline 6.2.3: Tables

Each cell in a table must have a number, a zero indicator, or a symbol indicating the reason that data are not displayed. Numbers in tables must comply with the following criteria:

  • All values in a vertical list of numbers must have the same number of decimal places. Use no decimal if all of the values in a vertical list are integers.
  • Use no greater precision than is warranted by the data (see section 6.6).
  • Only display zeros for values that are true zeros. If a value rounds to zero, use alternate symbols (BTS 2003b), such as --, to indicate that the estimate rounds to zero in the units being presented.
  • For sample-based zero estimates, use alternate symbols to indicate that the estimates are negligible, but possibly non-zero, in the population.
  • All tables that should logically sum to either 100 percent or some other numeric total must provide a note if the summation is affected by independent rounding or missing data.

Guideline 6.2.4: Graphs

Design graphs to maximize clarity and comparability within the information product and with other BTS products.

  • Design color graphs to show sufficient contrast if printed in black and white or viewed by a colorblind user. Web graphs need appropriate alternative text for use by screen readers. 
  • Graph titles and axis labels should be clear with no unexplained or undefined acronyms or industry jargon. In graphs with axes, indicate well-defined variable names and units for each axis. Both axes of a graph should be labeled with the names of variables, except where the axis label years is unnecessary because the years are shown.
  • Graphs that users are likely to compare should have similar scaling to facilitate the comparison.
  • Gridlines can be helpful to users if kept inconspicuous.
  • Minimize non-data clutter.
  • Minimize use of stacked bar or line graphs. They tend to present minimal information and are usually harder to interpret than simple tables or line graphs.
  • Do not use 3D graphs to present two-dimensional data
  • When using time intervals, spacing should be equidistant only if the intervals are equidistant.
  • In graphs, a vertical numerical axis should normally include zero or a break indicator (two slashes). If adding such a break is not reasonable due to software restrictions, add a note that the vertical axis is not zero-based.
    • For graphs showing relative quantities such as an index, zero is not a meaningful reference point. In such graphs, use the natural basis (such as 100) as a reference line in the graph.

Guideline 6.2.5: Statistical Maps

Statistical maps must comply with graph standards where applicable.

  • Use shadings for a statistical map that can be easily distinguished, even if reproduced in black and white.
  • Design category intervals to minimize the differences within classes and maximize the differences between classes. Limit the number of intervals to show better contrasts of shades. Three to five intervals should suffice.
  • Take care that the statistical map displays the data intended.
    • Use a scale consistent with the statistical information displayed.
    • Note that statistical area maps tend to emphasize geographic area versus other factors.
  • Provide an accuracy statement when appropriate. Note when data displayed in statistical maps have been collected locally and reflect varying methods of data collection.
  • Provide a distance scale and a legend that defines symbols and other graphic devices used in the map.
  • Map symbols and categories should be consistent throughout an information product and throughout series of related maps.

Related Information

Bureau of Transportation Statistics (BTS). nd. BTS Web Software Guidelines. Washington, DC.

__________. 2002. Section 508 Compliance Plan, Version 1.0. Washington, DC

__________. 2003a. BTS Excel Table Standards. Washington, DC.

__________. 2003b. BTS Guide to Style and Publishing Procedures. Washington, DC.

Energy Information Administration (EIA). 1998. EIA Guidelines for Statistical Graphs. Washington, DC. Available at as of April 19, 2005.

U.S. Department of Transportation (DOT). 2002. The Department of Transportation Information Dissemination Quality Guidelines, Section 5.1 (Publications and Disseminated Summaries of Data). Washington, DC. Available at as of January 19, 2005.

Approval Date: May 4, 2005

6.3 Text Discussion

Standard 6.3: Information should be presented clearly and objectively to the public, including a full disclosure of source(s).

Key Terms: confidential, objectivity, reliability, significant, time series, variance

Guideline 6.3.1: Presentation

Documents should be well organized with language that clearly conveys the message to the intended audience. Text discussion in information products must be consistent with accompanying tables, graphs, and maps, whether they are adjacent to the text or in other areas of the product. Include tables with text wherever possible.

Guideline 6.3.2: Sources

Data presented in the text that do not refer directly to the tables, graphs, or maps in the text must have a source reference (see Section 6.2.1).

  • Information used in BTS information products should come from known reliable sources.
  • Sources for which methodological information is unavailable (such as proprietary data) must include advisories indicating the lack of source and accuracy information.

Guideline 6.3.3: Data Discussions

Discussions of data should be objective and make statistically appropriate statements.

  • Fundamental changes within time series should be fully discussed. These changes may include, but are not limited to, changes to how the data were collected, changes in definitions, changes to the population, or changes in processing methods.
  • Statistical interpretations should indicate the amount of uncertainty. Only discuss differences or changes if the appropriate statistical tests verify their statistical significance. Terms such as confidential, reliability, significant, and variance should only be used in the statistical sense.
  • Avoid statements that imply a specific cause and effect relationship where one has not been established. Speculative statements about possible causes are acceptable if worded as speculation and not fact, and if supported by legitimate research citations.
  • No policy recommendations may be made regarding solutions to problems except with regard to data requirements.

Related Information

Bureau of Transportation Statistics (BTS). 2005. BTS Statistical Standards Manual, Chapter 5 (Data Analysis). Washington, DC.

Office of Management and Budget (OMB). 2002. Guidelines for Ensuring and Maximizing the Quality, Objectivity, Utility, and Integrity of Information Disseminated by Federal Agencies, Public Comments and OMB Response (Applicability of Guidelines). Federal Register, Vol. 67, No. 36, pp. 8453-8454. Washington, DC. February 22.

Plain Language Action & Information Network. nd. Writing User-Friendly Documents. Available at as of February 9, 2005.

U.S. Department of Transportation (DOT). nd. Plain Language Resource Page. Available at as of February 9, 2005.

__________. 2002. The Department of Transportation Information Dissemination Quality Guidelines. Washington, DC. Available at as of January 19, 2005.

Approval Date: May 4, 2005

6.4 Micro-Data Releases

Standard 6.4: Where confidentiality protections permit their release, release micro data (unit-level data) in a manner that facilitates its usefulness to the public. Documentation must be readily accessible to customers, provide the metadata necessary for users to access and manipulate the data, and clearly describe how the information is constructed.

Key Terms: metadata, micro data, record layout, standard error, variance, weight

Guideline 6.4.1: Software Accessibility

If micro data are released as an information product, all micro-data products and documentation should be made accessible without requiring the use of any one particular commercial product. Open source formats (ASCII text, space delimited, comma delimited, etc.) must be made available in addition to any others.

Guideline 6.4.2: File Description

Provide complete documentation for all data files.

  • Data producers should determine what metadata standards are current at the time data files are prepared and produce associated metadata for their files that comply with applicable standards.
  • Documentation must include a description of the data files including the title, data collection sources, tables that make up the set, inter-relation among tables (e.g., keys), and record layouts for data files.
  • Documentation must also include descriptions for each variable in the data set that includes the variable name, description, type (categorical, numerical, date/time, etc.), format, entry restrictions (e.g., categories, range), and missing value codes.
  • Indicate changes made to previously released data and the as of date of the data file.

Guideline 6.4.3: Information Quality Discussion

Micro-data files must include a discussion of how the data were collected and the limitations of the data (see Section 6.8).

Guideline 6.4.4: Items Needed for Variance Estimation

Datasets containing sample data must contain appropriate weights and associated variables for accurate variance estimation. A dataset that requires weights and additional variables for the computation of estimates and standard errors should not be released before these items become available.

Related Information

American Association for Public Opinion Research (AAPOR). nd. Best Practices for Survey and Public Opinion Research. Available at as of April 29, 2005.

International Organization for Standardization. 2002-2003. ISO/IEC 11179, Information Technology -- Metadata Registries (MDR), (multipart standard). Available at as of January 25, 2005.

Office of Management and Budget (OMB). 2005. Standards for Statistical Surveys (Proposed), Section 7.4 (Documentation and Release of Public Use Micro Data). Washington, DC. July 14.

Approval Date: May 4, 2005

6.5 Data Protection Prior to Dissemination

Standard 6.5: All information products must be released in accordance with applicable Federal law and regulations in conjunction with any confidentiality pledges given to data providers.

Key Terms: confidentiality, disclosure limitation

Guideline 6.5.1: Non-disclosure of Confidential Data

For information collected under a confidentiality pledge, employ statistical disclosure limitation procedures and methods to protect any identifiable or other confidential data from disclosure prior to public dissemination. BTS staff must follow the established confidentiality procedures outlined in BTS Confidentiality Procedures Manual (2004).

Guideline 6.5.2: Security of Disclosure Limitation Methods

The BTS confidentiality officer must review and approve any descriptions of disclosure limitation methods prior to their public dissemination.

  • Do not publish the details about how disclosure limitation methods were used to protect the data, if publication could jeopardize data confidentiality. For example, do not reveal information on how noise may have been added to the data, what variables were used to implement record swapping, or the parameter values used to protect tabular data.

Guideline 6.5.3: Disclosure Review Requirements

All information products must be reviewed for compliance with the disclosure protection procedures stated under the section, Disclosure Review Board, in the BTS Confidentiality Procedures Manual (2004).

Related Information

Bureau of Transportation Statistics (BTS). 2004. Confidentiality Procedures Manual. Washington, DC.

Bureau of Transportation Statistics Confidentiality Statute, 49 U.S.C. 111(k) as amended by the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users. P.L. 109-59.

Confidential Information Protection and Statistical Efficiency Act (CIPSEA) of 2002. P.L. 107-347, Title V.

Privacy Act of 1974, as Amended, 5 U.S.C. 552a.

Approval Date: May 4, 2005

6.6 Rounding

Standard 6.6: Use consistent practices for rounding and displaying numbers in text, tables, and figures.

Key Terms: precision, significant digit

Guideline 6.6.1: Using Rounded Numbers

All calculations should be made before rounding. In particular, tabulations to produce summary data and computations performed for purposes of estimating standard errors should be done on data as collected. No rounding should take place before completing these kinds of tabulations.

  • The sum of the rounded numbers may not equal the rounded sum. In such a case, add a note indicating that totals may not equal the sum of their individual components due to independent rounding.
  • To allow users to make further calculations accurately, do not further round estimates disseminated in a spreadsheet.

Guideline 6.6.2: Degree of Rounding in Text and Graphs

The degree of rounding for text discussion and graphs should depend on the type of data (actual measure vs. sample), the known or suspected accuracy of the data, and the differences being discussed.

  • Round percentages appearing in text to whole numbers unless smaller differences being discussed require decimal places and the accuracy supports it.
  • Perform rounding consistently for similar subjects throughout the information product.
  • In multiplying or dividing numbers, the resulting precision cannot be more precise than the least precise of the component numbers.

Guideline 6.6.3: General Rounding Rule

Consistent with BTS standard software (BTS nd), the general rules for rounding are:

  • If the first digit to be dropped is less than 5, then do not change the last retained digit (e.g., round 6.1273 to 6.127).
  • If the first digit to be dropped is 5 or greater, then increase the last retained digit by 1 (e.g., round 6.6888 to 6.69).

Related Information

Bureau of Transportation Statistics (BTS). nd. BTS Web Software Guidelines. Washington, DC.

Energy Information Administration (EIA). 2002. EIA Standards Manual, Standard 2002-15 (Rounding) and Standard 2002-15 Supplementary Materials (Guidelines on the Standard for Rounding). Washington, DC. Available at as of January 25, 2005.

National Center for Educational Statistics (NCES). 2002. NCES Statistical Standards, Standard 5.3 (Rounding). Washington, DC. Available at as of January 25, 2005.

Approval Date: May 4, 2005

6.7 Information Revisions

Standard 6.7: A standard process for handling possible post-dissemination data changes should exist and be documented.

Key Terms: external source, revision

Guideline 6.7.1: Scheduled Revisions

When appropriate, establish a schedule for anticipated revisions and make it available to users.

  • Identify the first dissemination of a data value in an information product as "preliminary" if revisions are anticipated in a subsequent dissemination.
  • Designate scheduled revisions to data values as "revised" (or final) when disseminating the changes.

Guideline 6.7.2: Errors in Previously Disseminated Information

Actions taken when data errors are discovered, or an external data source makes changes, are dependent on the impact that the potential revision would have on previously disseminated estimates.

  • Establish threshold criteria for making revisions. For example, the threshold criteria might be to revise for changes exceeding five percent in smaller values or exceeding one percent in larger values.
  • If the change does not exceed the threshold criteria, or threshold criteria do not exist, then management will determine whether the error is serious enough to warrant a revision.
  • Document the error discovery and correction process.

Guideline 6.7.3: Documentation of Error Corrections

Document the nature of the changes, any corrective action needed to fix an error, and provide this information to data users.

  • Identify data values changed due to unscheduled revisions and explain the reasons for these changes to data users.
  • Document problems regardless of the scope of the error or the decision whether or not to revise the data.
  • Provide error documentation to data users. Ensure timely and wide dissemination of information product revisions.

Guideline 6.7.4: Monitoring Revisions to Disseminated Data

Track the differences between an initial release of estimates and the corresponding final disseminated estimates for key data series.

  • Examine the effect of revisions (number of times data are revised and the magnitude of the revisions). Revision error information can help users better understand the variability between initial estimates and final estimates. For data systems that are continuously updated, compare the initial estimates with estimates obtained after a suitable period has elapsed.
    • Some ways to present revision error information include the average revision error, the maximum revision error, or the distribution of revision errors during a specified time period.
  • If revision error for a key data series shows an initial release is an unreliable indicator of the final estimate, consider whether publishing the estimate with a measure of revision error or withholding the initial estimate is the best way to serve data users.

Related Information

U.S. Department of Transportation (DOT). 2002. The Department of Transportation Information Dissemination Quality Guidelines, Section 6.4 (Data Error Correction). Washington, DC. Available at as of January 19, 2005.

Approval Date: May 4, 2005

6.8 Public Documentation

Standard 6.8: Documentation for the public must include the materials and tools (if applicable) necessary to properly interpret and evaluate disseminated information.

Key Terms: archive, reproducibility, transparency

Guideline 6.8.1: Source and Accuracy Information

Source and accuracy information should provide summary information suitable for posting on the web, and should be regularly updated to include methodological changes and the results of any quality assessment studies. Source and accuracy statements should summarize:

  • Data system objectives and frequency of information release,
  • Target population and coverage, geographic or other characteristic distribution and, where applicable, sample selection methodology and sample size,
  • Data collection methodology and content of forms,
  • Data adjustments for missing data, nonresponse, coverage error, measurement error, seasonality, and (if applicable) confidentiality protection,
  • Estimation methodology, including variance estimation methodologies for statistical samples,
  • Description of major sources of error, including coverage of the target population, missing data effects, and measurement error, and
  • A BTS point of contact for further questions and comments.

Guideline 6.8.2: Availability of Additional Documentation

To ensure the transparency of BTS information products, additional documentation (as specified in Chapter 2, Section 3.3, Section 4.6, Chapter 5, and Guideline 7.1.4) should be made available to customers upon request, unless such release would jeopardize confidentiality or disclose the actual methods used to protect the data.

Guideline 6.8.3: Reproducibility

Data users should be able to reproduce any publicly released information product to a reasonable degree of closeness. Information products that have been revised should clearly indicate the as of date.

Guideline 6.8.4: Archive Requirements

To ensure reproducibility within BTS, the product manager should establish criteria for retaining and archiving:

  • All electronic product files,
  • Complete information products, whether paper or electronic, representing a specific continuing publication product or one-time report,
  • The data files and/or databases (at the most disaggregated level), which are used to generate publicly released information products, and
  • System and model documentation and computer software/programs used to generate any information product.

Related Information

Bureau of Transportation Statistics (BTS). 2005. BTS Statistical Standards Manual. Washington, DC.

Office of Management and Budget (OMB). 2002. Guidelines for Ensuring and Maximizing the Quality, Objectivity, Utility, and Integrity of Information Disseminated by Federal Agencies. Federal Register, Vol. 67, No. 36, pp. 8452-8460. Washington, DC. February 22.

U.S. Department of Transportation (DOT). 2002. The Department of Transportation Information Dissemination Quality Guidelines, Section 5.3 (Source and Accuracy Statements). Washington, DC. Available at as of January 19, 2005.