Congress underscored the importance of statistical information for transportation investment decisions, policy initiatives, and other public actions when it established the Bureau of Transportation Statistics (BTS) in 1992 and required BTS to assess the state of statistics in an annual report. More than two decades after the creation of BTS, the transportation community’s emphasis on performance measurement—the process of collecting, analyzing, and reporting information on the performance of transportation systems—underscores the importance of data in decision making.

Progress made in compiling and distributing statistics on passenger travel, freight transportation, transportation’s role in the economy, and the unintended consequences of transportation is briefly summarized below. Box 9-A illustrates major accomplishments during the past year. This chapter also highlights the major transportation data gaps and the challenges and opportunities facing future transportation statistics programs.

Passenger Travel

Passenger travel data are collected by various government agencies, some periodically and others on a continual basis. The collection of these data can be categorized into two groups.

The first group collects overall system usage data without collecting data on individual travelers’ characteristics. The data programs in
this group include, but are not limited to, the following:

• the Highway Performance Monitoring System [USDOT FHWA HPMS 2010];
• the Federal Transit Administration’s National Transit Database [USDOT FTA NTD 2012]; and
• the Bureau of Transportation Statistics’ monthly passenger enplanement data [USDOT BTS 2012a],
• the National Census of Ferry Operators [USDOT BTS NFCO 2010], and
• the Intermodal Passenger Connectivity Database [USDOT BTS IPCD 2012b].

These data programs are crucial in the development of baseline information, the analysis of overall usage trends over time, and for understanding how changes in the economy influence the use of transportation systems.

The second group of passenger travel data programs collects data at the individual traveler’s level (without identifying personal identifiable information) from which travel patterns and traveler characteristics for the population as a whole can be estimated. The most prominent program in this group is the National Household Travel Survey (NHTS), sponsored mainly by the Federal Highway Administration (FHWA) and with increased cosponsorship by states and metropolitan planning organizations [USDOE ORNL 2012].

The NHTS collects not only information on individual trips but also demographic, household vehicle ownership, and neighborhood characteristic data as well as other factors that influence a household member’s decision on when, how, and how far to travel. Although the NHTS collects all personal travel taken by all modes of transportation, it mainly captures local travel. The high cost of conducting this type of nationwide survey has limited the frequency of this survey to once every 5 to 8 years. Despite these limitations, NHTS remains the only national source that provides the comprehensive data needed to understand travel decisions and predict travel demand.

The Census Bureau’s American Community Survey (ACS) is another commonly used source of passenger travel information. The ACS collects commute-to-work data from an annual survey of the population. This survey provides small-area information every year, unlike the once-per-decade information formerly provided by the decennial census. The ACS also provides statistics for small units of geography averaged over several years, while the 374 metropolitan statistical areas, as defined by the Office of Management and Budget, are the lowest levels of geography covered by the NHTS [USDOC ACS 2011].

Freight Transportation

Due to the complexity of freight transportation, there is no single data source that provides a comprehensive picture of annual freight movement from origin to destination, by all modes of transportation, and by all commodity types. Among the various data sources, the Commodity Flow Survey (CFS), cosponsored by BTS and the Census Bureau, serves as the backbone for developing a comprehensive picture of U.S. freight flows. The CFS is the only source of national- and state-level data on domestic freight shipments by manufacturing, mining, wholesale, and selected retail industries. It also provides comprehensive data on domestic hazardous material shipments. The CFS is conducted every 5 years as part of the Economic Census.

To develop an integrated national picture of freight movement, FHWA’s Freight Analysis Framework (FAF) relies on CFS data as its base and supplements that data with multiple, publicly available data sources, such as the data on freight flows across U.S. land borders and data on the international movement of air cargo collected by BTS [USDOT BTS 2012c]. The FAF also includes forecasts.

The performance of the Nation’s freight transportation system is primarily measured by freight travel time, which includes, but is not limited to, the following:

• for each major railroad, the average train speed and average wait time for loaded train cars to proceed;
• vessel delay times for transiting through each lock on the inland waterway system;
• truck speed and reliability on major highways and at border crossings; and
• productivity measures for selected ports.

The major national data sources for freight movement and performance are described at USDOT’s freight transportation website at freight.dot.gov.

Transportation’s Role in the Economy

In 2012 transportation-related expenditures as part of final demand accounted for nearly 8.6 percent of U.S. gross domestic product (GDP) in chained 2009 dollars and enabled linkages among natural resources, manufacturers, distribution centers, and consumers [USDOT BTS NTS 2013].

Transportation’s direct economic contribution is derived from statistics on the costs paid by households and businesses for transportation services, employment in transportation industries and occupations, and the value of transportation infrastructure and equipment. These statistics come from the Census Bureau, the Bureau of Economic Analysis (BEA), and the Bureau of Labor Statistics, each of which treats transportation as a significant sector of the economy.

For-hire transportation is one of the many sectors covered in the Economic Census, conducted every 5 years. This sector is also covered in the Census Bureau’s Services Annual Survey, which collects operating revenue and other industry-specific data. These data are used by the BEA to estimate the flow of expenditures among sectors of the economy in order to understand how changes in the costs in a specific sector affect the rest of the economy. BTS expands on this accounting in its Transportation Satellite Account to include the sizable contribution to the economy made by in-house transportation services within nontransportation industries, such as truck fleets operated by large retail companies.

Transportation is not often highlighted in monthly national economic statistics. To provide a perspective on transportation’s role in a dynamic economy, BTS developed the monthly Freight Transportation Services Index (TSI) [USDOT BTS TSI 2012d]. This index is based on activity in all modes of for-hire freight transportation services, and affords a better understanding of the relationship between transportation and the current and future course of the economy. The Freight TSI is being expanded to include in-house transportation to provide a complete picture.

Transportation and its Unintended Consequences

In addition to the intended economic activity that transportation creates, it has unintended impacts on safety, energy consumption, the environment, and communities. Of these, safety dominates the statistical activities of the USDOT. The National Highway Traffic Safety Administration (NHTSA) and the Federal Motor Carrier Safety Administration account for 40 percent of the expenditures on major statistical programs in the Department [USEOP OMB 2013b]. One major safety data effort is the modernization of NHTSA’s National Automotive Sampling System (NASS) General Estimates System (GES) to ensure the reliability and timeliness of safety data collection and analysis. The Pipeline and Hazardous Materials Safety Administration and FHWA also have largescale safety programs in place. Altogether, the Department’s annual expenditures on safety data exceed $50 million.¹

Recognizing that roadway safety improvement requires stronger partnerships and collective efforts across all modes of transportation and stakeholders, senior USDOT leadership initiated the development of the Roadway Safety Plan to bring an integrated focus to roadway safety issues [USDOT OST RSP 2012]. One of the priorities of this plan is to improve the systematic collection of safety data and analytical tools. These improvements are intended to facilitate the identification of high-risk road users and commercial vehicle operators,  rioritize safety investment decisions, and evaluate the effectiveness of safety measures.

The relatively low fatality rates in nonhighway modes, such as commercial aviation, railroads, and transit, do not reduce the need for data to understand risks and maintain or improve the safety of these modes. The focus of data programs for nonhighway modes has shifted from determining causes of crashes to understanding circumstances surrounding near misses or other mishaps that could have resulted in a serious incident. The National Aeronautics and Space Administration (NASA) provides a close calls reporting system for the Federal Aviation Administration that allows airline employees to make confidential reports that can be used to identify and mitigate safety problems. Nearly 5,000 reports are filed each month [NASA 2012]. NASA provides a similar reporting system for Amtrak. BTS has initiated the first urban close calls reporting system with a major transit system. The BTS program is also being expanded to a Class I railroad and off-shore oil extraction and connecting pipeline operations.

The transportation sector accounts for more than two-thirds of the petroleum consumed in the country and produces between one-quarter and one-third of all of the carbon dioxide  CO2) emitted by the Nation’s energy consumption. The U.S. Department of Energy has a major data program that tracks energy consumption by transportation sector [USDOE EIA 2012], and transportation’s contributions to greenhouse gases and other emissions are tracked by the Environmental Protection Agency [USEPA OTAQ 2012]. While individual agencies compile information to meet specific needs, integrating these data and developing analytical techniques from many disciplines are the keys to effectively using these data sources to reduce transportation-related energy consumption and emissions. For example, the relationships between vehicle usage patterns and energy usage intensity are crucial to measuring and assessing the effectiveness of different energy and emission reduction opportunities and policies. Unfortunately, with the discontinuation of the Vehicle Inventory and Use Survey in 2002, much of the data necessary to help make these assessments are now more than 10 years out of date [USDOC CB VIUS 2002].

Data Gaps and Challenges

To understand transportation activity, its contributions to the economy, consequences for the environment, and the potential impacts of policies and investments, it is crucial to estimate the interactions among the following components:

• sectors of the economy that produce the demand for transportation and depend on transportation for productivity and health;
• the response of businesses within supply chains to regulations, private and public investment, and the impact those responses have on both the time and location of transportation activities;
• household mobility needs and expenditures that determine the time and location of transportation activity and how travelers respond to transportation investments and regulations;
• infrastructure and assets that are needed to serve the mobility requirements of households and businesses, to stimulate local economic growth, and to mitigate the adverse safety and nvironmental impacts of passenger and freight transportation; and
• transportation investments that improve transportation services and promote economic growth and global competitiveness; and
• transportation’s role in economic development. 

To better understand these interactions, BTS and its partners continue to collect data through traditional approaches (e.g., surveys), mine data sources not originally designed for statistical purposes (e.g., administrative records), explore information from mobile devices (e.g., Global Positioning System and radiofrequency identification), and improve modeling approaches to fill data gaps.

Tables 9-1 and 9-2 highlight the strengths and weaknesses of statistics compiled from these surveys, administrative records, monitoring technologies, and models. Major data gaps include the following:

• intercity passenger travel by surface modes of transportation and general aviation,
• transportation provided by social service agencies and nonprofit organizations,
• the domestic transportation of international trade,
• local freight movement,
• the condition and performance of freight railroads,
• the current condition of transit infrastructure,
• the cost of freight transportation,
• in-use fuel economy of motor vehicles,
• noise related to surface transportation facilities, and
• disruptions to natural and cultural environments.

In some cases a data gap affects multiple topics. For example, exposure to safety risks cannot be estimated without a complete picture of where and how people travel.

Of the major data gaps, intercity passenger travel is particularly significant. Long-distance travel by all modes and by demographic characteristics of the traveler has not been measured since 1995. Recent discussions about trends in passenger travel are limited to local travel. This limitation may result in misguided conclusions because long-distance travel involves different trip purposes and conditions than local travel, and one long-distance trip can generate as many miles of travel as dozens or even hundreds of local trips.

Challenges facing BTS and its partners are not limited to filling data gaps. The simple availability of data does not assure that effective statistics exist to help answer the questions of decision makers. Significant quality issues and the lack of methods for summarizing data into useful information can undermine the effectiveness of key data programs. All data sources have quality issues, but some questions about statistical quality have greater potential consequences for public perceptions and decision making.

Geospatial data provide another quality challenge. BTS compiles data from a variety of sources for its National Transportation Atlas Database and provides a web-based application to access and visualize the data. Errors and inconsistencies in the data are revealed when users zoom in on very small areas.

The digital revolution presents the biggest opportunities and challenges for improving transportation statistics to support public decisions. Nearly all business transactions are now electronic, as are a growing share of personal transactions. The databases created by business transactions and credit card purchases, communications systems, traffic management systems, and onboard vehicle diagnostics can be mined to estimate passenger and freight movement, identify the costs to travelers and businesses of those movements, and even measure the emissions created by vehicles in motion or idling. The coverage of databases continues to expand and the tools for mining them, popularly known as Big Data, Data Analytics, and similar terms, have improved dramatically. Technology promises timelier, more accurate, and less expensive data, especially when compared to data provided by surveys.

Technology-based data typically provide narrower windows on the phenomena being measured than do surveys and place a premium on data integration and statistical representation. Technology also raises major privacy, confidentiality, and intellectual property issues. Beyond improved data collection and processing applications, technology shows promise in enhanced understanding of transportation activities and impacts. The processing power of personal computers creates opportunities for widespread use of new analytical and visualization techniques.

The Challenge of Performance Measurement

MAP-21, the Moving Ahead for Progress in the 21st Century Act of 2012 (Public Law 112-141) requires states and the USDOT to publish performance measures and progress toward performance targets for many aspects of surface transportation. These requirements reflect a growing emphasis on accountability and management for improved performance in all fields of public administration. Performance measurement involves many statistical challenges and opportunities in addition to institutional concerns for the transportation community.

MAP-21 and the Government Performance and Results Act (GPRA) (Public Law 103-62) ask whether government actions are making a difference. The answer requires statistics beyond basic indicators of a general condition, such as the number of fatalities, tied to a generally stated goal, such as improved safety. More detailed statistics and more complex analysis are typically needed to answer the questions identified in this law.

Performance measures are typically defined as output or outcome measures, though many performance measures are actually basic indicators that reflect goals or basic conditions. For example, the number of fatalities is a basic indicator. Fatalities by cause provide a more useful measure against which outputs and outcomes can be considered.

Outputs of government programs should be relatively easy to define, except that programs often involve a variety of specific actions that are difficult to characterize in simple measures. Furthermore, the output of one program may be the input of another. The major output of Federal agencies implementing MAP-21 is spending on safety and other aspects of surface transportation. The outputs of recipients of Federal funds may involve a wide variety of facilities and services purchased with those funds. Statistics on the facilities and services may be lacking for formula grant programs, leaving total expenditures as the only available measure of output.

While outputs should be relatively easy to define in most cases, outcomes are the most difficult to measure. Outcomes are not just changes in an actionable condition following an output. Simple correlation is not enough. To be an outcome, some evidence of causality is required from targeted monitoring, such as before and after studies.

Given resource limitations for expensive new data collection programs, managers of transportation statistics will be challenged to adapt existing data program and analytical techniques to serve performance measurement. For example, current transportation planning models and supporting data are designed to measure problems, such as congestion, and predict how proposed changes, such as increased capacity, will affect those problems. Research is underway to estimate basic indicators and actionable conditions with these models and use forecasting elements to set targets by which actual outcomes can be judged.

Performance measurement will ultimately require some new data collection. MAP- 21, GPRA, and the American Recovery and Reinvestment Act of 2009 (Public Law 111-5) all encourage the development and publication of better output and outcome measures. Outcome data from before-and-after studies and other quasi-experimental designs that measure program effectiveness can both serve performance measurement and become a new source of data for planning models.

Priority Areas Requiring FocusedAttention by BTS

MAP-21 and its successor legislation establish priorities for transportation statistics in the years ahead. MAP-21 reaffirms the mandate for BTS and adds the establishment of a safety data program on behalf of the Secretary. MAP- 21 requires performance measurement for most surface transportation programs, such as safety improvement and infrastructure preservation. MAP-21 also adds new provisions for freight transportation that require data, including designation of freight corridors, development of investment analysis tools, and creation of a national freight strategic plan and state freight plans. MAP-21 also encourages states to maintain a base map of all public roads on which fatal and serious injury accidents can be located and analyzed.

To support decision making throughout the transportation community, BTS continues to seek better ways to develop and report statistics on the extent, use, condition, performance, and consequences of the transportation system. Major initiatives include the following:

• Improve the usefulness of existing statistics, including an expanded Facts and Figures series of reports to visualize key statistics on current topics and a new National Transportation Atlas application to explore geographic data on the web.
• Based on the Freight Analysis Framework, establish a National Commodity Origin- Destination Account. It will integrate with the Commodity Flow Survey, the Transborder Freight Data Program, and other public data to form a complete and timely picture of freight movement throughout the Nation as well as serve as a model framework for creating the National Travel Origin-Destination Accounts for a similar picture of passenger travel.
• Develop improved economic statistics, especially related to the value of transportation infrastructure.
• Fully implement the Open Data Policy under Office of Management and Budget memorandum M-13-13 of May 9, 2013 to make transportation data and research findings transparent and accessible to the public, inspiring actions to improve the quality of underlying data and encouraging the creative use of that data [OMB 2013a].
• Explore administrative records and advanced data mining analytics (e.g., Big Data) to measure phenomena like passenger travel for which traditional surveys are decreasingly effective.
• Continue to work with other agencies to enhance the quality and integrity of transportation statistics, acting as the champion for better transportation statistics among other Federal agencies

Some of these BTS initiatives will address several of the gaps and challenges discussed above, and some will explore identified opportunities. Through these and other efforts, BTS will continue to strive toward achieving the vision of Abraham Lincoln who said, in reference to proposed Federal investments in transportation facilities, “Statistics will save us from doing what we do, in wrong places [Lincoln, A; 1848, pp. 709-711].”

References

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—2012b. Intermodal Passenger Connectivity Database (IPCD) Available at http://www.transtats.bts.gov as of September 2012.

—2012c. Transborder Freight Data Program. Available at http://transborder.bts.gov as of September 2012.

—2012d. Transportation Services Index (TSI). Available at http://apps.bts.gov as of September 2012.

—2013. National Transportation Statistics (NTS). Available at http://www.bts.gov as of September 2012.

U.S. Department of Transportation (USDOT). Federal Highway Administration (FHWA).

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—2011. Highway Statistics. Available at http://www.fhwa.dot.gov/ as of May 30, 2014.

—2012. Highway Statistics. Available at http://www.fhwa.dot.gov/ as of May 30, 2014.

U.S. Department of Transportation (USDOT). Federal Transit Administration (FTA). National Transit Database (NTD). Available at http://www.ntdprogram.gov/ as of September 2012.

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—2013a. Open Data Policy: Managing Information as an Asset, Memorandum for the Heads of Executive Departments and Agencies (May 2013). Available at http://www.whitehouse.gov/ as of September 2014.

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¹ Office of Management and Budget, Statistical Programs of the United States Government: Fiscal Year 2013 (November 26, 2013), p. 88. Available at http://www.whitehouse.gov/ as of August 2014.