Chapter 8 - State of Transportation Statistics

Chapter 8 - State of Transportation Statistics

State of Transportation Statistics

Bicycles parked at National Airport Metrorail station in Arlington, VA.

Bicycles parked at National Airport Metrorail station in Arlington, VA

People and organizations make innumerable transportation decisions every day, including when, where, and how to travel and ship goods, what investments to make in equipment and infrastructure, and how to deal with the negative consequences of transportation. To make the transportation system work effectively and efficiently, decisionmakers in both the public and private sectors need good information. A wealth of information is currently collected, analyzed, and disseminated by a variety of organizations, but a number of questions arise about the data.

1. Do we have data on the right subjects?

2. Are the data reliable and accurate?

3. Are the data understandable, accessible, and timely for decisionmaking?

The Bureau of Transportation Statistics (BTS), established in 1992 as an administration within the U.S. Department of Transportation (DOT), has key data responsibilities in the domain of transportation. BTS's mandates, reaffirmed by reauthorization legislation in 1998, are to support the data-collection programs that already exist in DOT, to ensure that these programs provide data of adequate quality for the decisions they support, to identify data gaps, and to analyze all data pertinent to transportation in support of policymaking and evaluation.

Transportation decisionmakers need data that are relevant, high quality, timely, and complete, and ideally, the data should be comparable with other available data. Many reports over the years have pointed to the need for such data [1 ,2 ,3]. While improvements have been made, shortcomings remain. For instance, timeliness continues to be a problem. Much available data in key transportation areas may be a year or even several years out of date when they are publicly issued. Examples include the Federal Transit Administration's National Transit Database, the Federal Highway Administration's Highway Performance Monitoring System, and BTS's American Travel Survey. Data gaps remain in several areas, such as the location, mode, and other characteristics of U.S. imports and exports, congestion, and transportation's impact on groundwater, animal habitat, and land use [6, 7]. Some data currently collected fail the test of relevance for decisionmaking, particularly for local decisionmakers. For instance, the Commodity Flow Survey collects much national and state freight data, but many of the decisions about freight infrastructure are made locally. Information is also needed about freight movement at the metropolitan level.

To address these issues, BTS developed in 2000 a strategic five-year plan for transportation statistics (see box 1) and has undertaken several initiatives that fall broadly into three areas: 1) data collection, 2) data quality, and 3) data compilation, storage, and dissemination.

Data Collection

BTS and many other organizations collect data on myriad aspects of the transportation system, such as airline and motor carrier operations, freight flows, passenger characteristics and movement, energy consumption, environmental impacts, and makeup of the transportation system itself. The following areas are illustrative of some of these data collections.

Airline Data

BTS's Office of Airline information (OAI) collects and publishes on-time data for airlines, as well as more extensive operating data for both domestic and foreign airlines. OAI also collects detailed financial statistics for domestic airlines and various statistics on service quality. The data reporting is mandated by law, and several issues are now driving changes in the reporting regulations. Public concern about airline delays led to legislation requiring better data on the causes of delay-a DOT/industry task force has made several recommendations and rulemaking will follow. The department also has been working for some time to modernize the data-collection program, bringing it up to date with changes that have occurred in the airline industry, and to take advantage of advances in information technology to reduce the data-collection burden.

Motor Carrier Data

BTS collects financial and operating data from for-hire trucking and passenger bus companies with annual operating revenues over $3 million (equivalent to a fleet of about 25 to 30 vehicles). BTS is undertaking an effort to improve the completeness, accuracy, and timeliness of the motor carrier financial and operating data. In addition, the database of trucking companies that might be subject to reporting has been updated. In December 2000, a series of outreach sessions was held to work with trucking companies toward better and more complete data.

Transportation System Data

Coordinated by BTS, the Omnibus Survey is a DOT-wide effort aimed at collecting information about the transportation system, how it is used, and how users view it. Information is gathered each month from a randomly selected sample of 1,000 households. In addition to a core set of questions, each month the Office of the Secretary and/or modal administrations can propose new questions for inclusion in that month's survey. Survey results are available within 30 days of the mailout, and the analysis is completed within the next month or sooner, if necessary. The results of the first Omnibus Household Survey were made available in August 2000, and the report that was issued highlighted safety. Targeted surveys aimed at specific topics are also planned. Omnibus Surveys are intended to provide timely snapshots of highly visible issues, but are not intended to substitute for more comprehensive data-collection efforts.

Freight and Passenger Data

Sample surveys sponsored by BTS in conjunction with agencies such as the Census Bureau and the Federal Highway Administration include the Commodity Flow Survey and the National Household Travel Survey. Freight data are collected by the Commodity Flow Survey, a survey of freight shippers that includes shipment variables such as mode, commodity, weight, value, and distance. Passenger data, both long-distance and local passenger travel by American households, are collected in the National Household Travel Survey (formerly the Nationwide Personal Transportation Survey and the American Travel Survey), sponsored by BTS and the Federal Highway Administration. The joint survey gathers trip-related data such as mode of transportation, and duration, distance, and purpose of trip. It also gathers demographic, geographic, and economic data for analysis purposes. These two surveys are conducted about every five years. While providing national benchmarking, the surveys have been too infrequent to track fast-moving changes in transportation.

Energy and Environmental Data

Most of the data needed to track transportation energy and environmental issues have long been outside the purview of DOT. Data on energy are collected or estimated by the Energy Information Agency (EIA) of the U.S. Department of Energy. The U.S. Environmental Protection Agency (EPA) provides a variety of data in the environmental area. Some examples are: estimates of air pollutant emissions from the use of transportation vehicles, emissions data from manufacturers of transportation equipment and petroleum refining, estimates of the disposed amount of some types of transportation equipment, and data obtained by monitoring air quality across the nation.

Both EIA and EPA make annual estimates of transportation's greenhouse gas emissions, which may contribute to global climate change. While both agencies use EIA survey data on energy consumption as a basis for their estimates, their coverage and methodologies differ, resulting in different datasets. Research in 2000 by the DOT Center for Climate Change and Environmental Forecasting led to a finding that some fundamental data on freight modes is unavailable leading to estimates of freight greenhouse gas emissions that are inferior to those on passenger vehicle emissions. The Center has initiated a study to determine the level of effort needed to improve these data estimations.

Data Gaps

Gaps in data may involve the absence of data, data that are of poor quality, or data that are collected but not provided in a timely manner or in a form that a decisionmaker can use. For example, a known major data gap is the absence of good inland U.S. origin/destination data for traffic moving in international commerce. A BTS project is currently underway to assess gaps in transportation data and the benefits and costs of possible solutions. This process involves consultation among major stakeholders including those within DOT and congressional staff, state DOTs, metropolitan planning organizations, the transportation industry, and research organizations.

Data Quality

DOT leadership and customers have identified data quality as a high priority, cross-modal problem. Data issues currently being addressed include safety, performance measures, and hazardous materials.

Safety Data Action Plan

One major effort is now underway in support of DOT's strategic goal to promote public health and safety by working toward the elimination of transportation-related fatalities, injuries, and property damage. This Safety Data Action Plan, developed with stakeholders and approved by the DOT Safety Council, has six recommendations for improving the quality, timeliness, and relevance of transportation safety data. They are to:

1. establish a lead agency to ensure intermodal collaboration,

2. develop an intermodal database,

3. develop data standards,

4. improve data quality,

5. expand transportation resources, and

6. conduct focused research projects to address data shortcomings (see box 2).

Performance Measures

Accurate, timely, and comparable transportation data will improve the credibility and thus the utility of statistics needed for performance measurement. The DOT fiscal year 2001 Performance Plan identifies performance indicators and goals that will be used to measure progress in achieving strategic goals [5]. To help in the performance measurement process, BTS is working with other DOT administrations to develop a framework to identify and implement best current statistical practices for data collection. A compendium of source and accuracy statements has been developed for each of the data programs used in the performance report. Efforts are underway to develop departmental statistical standards and implement other steps to assure accurate data. The DOT Office of the Inspector General will verify and validate performance measures on a selective basis each year.

Hazardous Materials Data

The Secretary of Transportation delegated authority to BTS in coordination with the Associate Deputy Secretary to work with DOT administrations to determine data needs, collections strategies, and analytical techniques appropriate for implementing the department's hazardous materials program. This delegation of authority was recommended in a departmentwide evaluation of the hazardous materials transportation program co-chaired by the Office of the Inspector General and the Research and Special Programs Administration (RSPA) [4]. The report also recommended that BTS lead a project to identify data needs, identify and implement ways to improve the Hazardous Materials Information System and the Unified Shipper Enforcement Data System databases, and work with RSPA to design a process to more fully evaluate and analyze incident data. Quality improvements must be made database by database.

Database Audits

At the request of Congress, BTS recently audited four transportation databases and found a wide range of quality issues and opportunities for improvement. The four databases audited were the Enhanced Traffic Management System (ETMS), the Metropolitan Intelligent Transportation Systems (ITS) Deployment Tracking Database, Office of Intelligence and Security (OIS) Survey of DOT Operating Administrations, and the Merchant Mariner Licensing and Documentation System (MMLD). The ETMS data were not subject to errors large enough to impair their primary use. Both the Metropolitan ITS Deployment Tracking Database and the MMLD system were of reasonable quality, but both contained some systematic errors due to missing, incomplete, or inaccurate data records. However, the data contained in the OIS Survey of DOT Operating Administrations were found to be unusable and possibly misleading because of high levels of sampling and nonsampling error.

Other databases to be assessed include the Highway Performance Monitoring System, motor carrier safety, seat belt usage, runway incursions, recreational boating accidents, and grade-crossing safety. Altogether, BTS has agreed to perform a quality review of about 80 major databases. The result in each case will be a report to the database administrator with specific recommendations for quality improvement.

Compiling, Storing, and Disseminating Transportation Data

Transportation data are of little use if they are not available and accessible to decisionmakers and others. Historically, decisionmakers have had to make do with datasets that essentially age between collection and publishing cycles. Now, largely because of the Internet, this static system is being replaced by one that offers highly dynamic capabilities. As soon as compiled data are checked for quality, they can be immediately shared with potential users worldwide.

A number of efforts are underway at BTS and elsewhere to make data more accessible. These include the Intermodal Transportation Database (ITDB), the National Transportation Library (NTL), geographic information systems, Transportation Indicators, and international trade data.

Intermodal Transportation Database

The ITDB will eventually provide one-stop shopping for a large number of transportation-related databases. Although current data programs will continue to collect and record data in their usual ways, the ITDB will create a unified interface that allows seamless integration of multiple datasets. Thus, users can obtain all the available information from a single source, in a uniform format, rather than having to contact multiple sources, some of which have data programs that many users may find difficult to manipulate. Additionally, the ITDB will provide standard-format documentation and a user-friendly front-end that will support an expanding array of statistical analyses, statistical graphics, and geographic displays.

The initial databases in the ITDB will be those called for by Congress in the Transportation Equity Act for the 21st Century (TEA-21): freight and passenger volumes and patterns of movement, the location and connectivity of transportation facilities and services, and transportation expenditures and capital stocks. Other transportation data related to areas such as safety, energy, the environment, and demography are expected to be available through the ITDB.

National Transportation Library

The NTL is an electronic "virtual" library, available only on the Internet, providing broad access to the nation's transportation research and planning literature. Congress directed the establishment of the NTL in TEA-21. Currently, the NTL contains over 150,000 documents and abstracts for another half million documents.

Geographic Information Systems

Geospatial data can be graphically portrayed in ways that are compelling for decisionmakers. BTS creates, maintains, and distributes geospatial data through the National Transportation Atlas Database program, outlined in TEA-21 legislation. These data are obtained from multiple sources and include the National Highway Planning network, a national rail network, public-use airports and runways, and Amtrak stations. In the near future, layers will be added for land use, waterways, transit, ITS, and satellite imagery. Together, these data comprise the transportation layers of the National Spatial Data Infrastructure. This program distributes transportation geodata and a number of geographic reference files including state, county, congressional district, and metropolitan statistical area boundaries.

Transportation Indicators

BTS has developed a set of transportation indicators published each month on the BTS website. The indicators fall into two broad categories: those that provide context about the economy and society in which transportation functions and those that convey interesting information about an aspect of transportation. Drawn from a wide variety of sources, the indicators are intended to provide decisionmakers with as timely data as possible, using quarterly, monthly, and in some cases, weekly information. The process of developing the indicators has helped to draw attention to data gaps, such as areas where data are out of date or where reliable data are unavailable. To address some of these concerns, research is planned to develop new indicators or to improve timeliness of data where practical.

International Trade Data

In an era of globalization, trade and transportation data are closely connected. BTS compiles, analyzes, and publishes information on U.S. foreign trade, variables that may influence U.S. global competitiveness, key international trends in transportation, and comparative statistics on transportation in various countries. These data provide context for understanding how the U.S. transportation system might be affected by exports, imports, and international travel, and set the stage for harmonizing international data. While the data may be published in printed format, much of these data are available on the BTS website. BTS also works closely with its statistical counterparts in Canada, Mexico, and many other countries, through a variety of exchange and collaborative activities.

Using Information Technology

Attention is also being focused on advances in information technology and its implications for providing timely data that can be collected unobtrusively. For instance, BTS currently collects a 10 percent sample of airline tickets sold by air carriers. Information on airline tickets is also processed through an industry clearinghouse to allow the allocation of revenues when travel is not completed on the ticketed airline. This clearinghouse information is a potential source of data on the patterns and prices of commercial airline travel in the United States. The advantages of using these data would include: the reduced burden on the airlines through elimination of the current survey; high-quality data because there will be no errors due to sampling or itinerary changes; and timeliness, because of the highly automated process. Another example of data derived from information technology is highway operational data automatically collected by traffic agencies as a result of the implementation of advanced traffic management systems. Such data could be used as a source of very timely information on metropolitan traffic patterns and performance.

Transportation Workers

To date, little attention has been focused on the transportation workforce that, like the population in general, is aging. As a result, the transportation industry has begun to forecast serious shortfalls of skilled labor. Some sectors may be hit harder than others, depending on the growth of the sector and the age distribution of the existing workforce. In order to provide data for decisions on workforce development, BTS is planning to improve the collection and analysis of data in this area.

Economics and the Transportation System

Another important topic that needs more attention is how to pay for the transportation system. Financing of the transportation system has been a central issue for many years, but there are still limited data spanning the entire system-including federal, state, local, and private sector investments. BTS is planning a project to estimate the demand for transportation funding at all levels of government over the past 10 years and the likely demand in the future. This will be matched with data on revenue to identify shortfalls or surpluses in the transportation financial system.

The Transportation Satellite Accounts is a joint effort of BTS and the Bureau of Economic Analysis (BEA) to provide a detailed picture of transportation in the nation's Gross Domestic Product (GDP). By enhancing the data used in constructing GDP estimates, BTS and BEA have been able to quantify detailed values for input-output models that allow in-depth resolution of the economic interactions between specific categories of transportation and other segments of the U.S. economy. A key feature of this work is the estimation of the in-house transportation sector, transportation services provided by firms in nontransportation sectors of the economy. This includes, for instance, trucks owned and operated by a grocery chain. Until recently, reliable estimates of this sector did not exist.

Furthermore, through a collaborative research effort, BTS and BEA have been developing a method for "capital stock accounting" to measure the value of the nation's transportation infrastructure, as directed in the TEA-21 legislation. This supports efficient asset management and enables other DOT modes to forecast remediation requirements. Initial data are expected in Fall 2001.


Advances in transportation and communications technologies have facilitated commodity production and consumption, allowing it to take place at greater speeds and on a global scale. In order to keep pace with these advances, decisionmaking must be increasingly rapid, flexible, and have broader geographical scope.

Data systems designed to support decisionmaking must provide the right data at the right time. Moreover, data must be accessible to a wide variety of actors with varying degrees of sophistication in data handling and analytical capabilities. Most daily operational transportation decisions are made at the state and local level. Federal agencies collect data from state and local entities largely for policy development and enforcement purposes, and the ways in which these data are ultimately presented and disseminated need to be made relevant to the needs of state and local decisionmakers.

Fast and flexible worldwide production and consumption has also raised the profile of intermodal transportation for both people and goods domestically and internationally. The increasingly intermodal environment must be supported with data that are comparable across modes and countries and measures movements from origin to destination.

1. Transportation Research Board, Data for Decisions: Requirements for National Transportation Policy Making, Special Report 234 (Washington, DC: National Academy Press, 1992).
2. Transportation Research Board, National Research Council, The Bureau of Transportation Statistics: Priorities for the Future, C.F. Citro and J.L. Norwood, eds. (Washington, DC: National Academy Press, 1997).
3. ____. Information Needs to Support State and Local Transportation Decision Making into the 21st Century (Washington, DC: National Academy Press, 1997).
4. U.S. Department of Transportation, Departmentwide Program Evaluation of the Hazardous Materials Transportation Programs (HMPE,) available at, as of April 2001.
5. ____. FY 1999 Performance Report/FY 2001 Performance Plan (Washington, DC: 2000).
6. U.S. Department of Transportation, Bureau of Transportation Statistics, Bicycle and Pedestrian Data: Sources, Needs, and Gaps (Washington, DC: 2000).
7. ____. Transportation Statistics Beyond ISTEA: Critical Gaps and Strategic Responses (Washington, DC: 1998).