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Publication Number:  FHWA-HRT-16-082    Date:  August 2017
Publication Number: FHWA-HRT-16-082
Date: August 2017


Federal Highway Administration Research and Technology Evaluation: National Household Travel Survey Program Final Report

Executive Summary

Purpose of the Evaluation

The National Household Travel Survey (NHTS) Program, funded by the Federal Highway Administration (FHWA) through the Office of Highway Policy Information (OHPI), is one of the programs being evaluated under FHWA’s Research and Technology (R&T) Evaluation Program. Given the massive scale of this data collection effort—a yearlong survey that reaches 150,000 households—and the associated costs of collecting these data, FHWA wanted to better understand the longer-term impacts of the program.

Program Description

FHWA has conducted national travel surveys for more than 45 years. The surveys are conducted periodically (generally once every 6–8 years) and provide the only data in the country that link individual personal travel behavior, household demographic and socioeconomic characteristics, traveler attitudes, vehicle ownership, and vehicle attributes. In addition to the national sample, States and metropolitan planning organizations (MPOs) may purchase an additional, or “Add-on” sample. The 2009 NHTS consisted of a national sample of 25,000 households and an Add-on sample of 125,000 households. Currently, NHTS is planning its upcoming 2016 survey.


The Volpe team identified four impact areas that comprise the Evaluation, each summarized as follows:

For each impact area, evaluation questions were developed along with key performance measures. The data collection was primarily qualitative in nature, including a literature search, document review, and indepth interviews. Quantitative data were only used in measuring the breadth and depth of NHTS use, including NHTS website usage statistics (http://nhts.ornl.gov/) and an analysis of the 2014 NHTS Compendium of Uses, an annual compilation of publications that cite the NHTS.(1)


Breadth and Depth of Use

An analysis of the 2014 NHTS Compendium of Uses demonstrates that 46 percent of publications are primarily transportation focused, but more than half of publications have a primary application in other fields that are connected to transportation, including energy (25 percent), survey methods or analysis (12 percent), environment (9 percent) and health (8 percent). Across fields, 45 percent of publications pertain to national level analysis, 30 percent are international, and 25 percent deal with State or regional issues or topics.(1) Across the different fields, the publications address a variety of transportation topics, and, in most cases, multiple topics are covered in a single publication.

The NHTS Compendium of Uses were analyzed from 2011 through 2014.(1–4) During this period, Volpe found that the number of citations increased from 210 to 313, and the citations with a primary focus in fields that are connected to transportation (e.g., health, environment, energy, and methods) grew significantly, from 28 to 44 percent of all publications.

Two sources of data were used to identify the NHTS users: the 2014 NHTS Compendium of Uses and a compilation of lead presenters at NHTS-sponsored conferences, workshops, or Transportation Research Board (TRB) sessions.(1) In the Compendium, Volpe found that a large majority of the publications are produced by academics (82 percent); however, the lead presenters’ analysis demonstrated a greater mix of NHTS users, as 41 percent are comprised of academics, 27 percent are Federal, 22 percent are contractors or consultants, and 7 percent are MPOs. It should be noted that these findings on lead authors provide only a snapshot of users based on two distinct data sources. Through documents and interviews analyzed below, Volpe learned that NHTS users (both within and outside of Government) are regularly developing documents, reports, models, statistics, and other outputs that are not published or publicly distributed and hence are not included in these analyses.

Website usage statistics[1] offer another snapshot of NHTS use. From July 2013 through May 2015, the statistics indicate robust usage, with 8,443 visits to the website and 4,225 unique visitors in May 2015. NHTS Publication (PDF) views and tool activations seem to be driving visits in this period.(5)

Impacts on Policy, Project, or Regulatory Decisionmaking

NHTS clearly informs decisionmaking, but it is difficult to identify all impact cases, as policy proceedings and legislative hearings are not often transcribed and/or readily available, and oftentimes, the data sources (e.g., NHTS) for policies and legislation are not formally cited. As a number of interviewees explained, it is difficult to trace the decision output(s) of the NHTS, but it plays a critical role in providing context and an understanding of the travel behavior landscape, thus laying the foundation for decisionmaking. Through the interviews and document review, Volpe was able to identify several examples or cases that demonstrate the role of NHTS in the decisionmaking process.

At the Federal level, NHTS informs the writing of U.S. Department of Transportation (USDOT) reports and initiatives, the development of legislation (particularly during re-authorization), and the creation of Federal regulations. A recent example includes USDOT Secretary Foxx’s Beyond Traffic: Trends and Choices, where NHTS data are informing the national dialogue on the state of and future direction of transportation.(6)

With respect to legislative uses, Volpe found that NHTS data are cited extensively in the 2013 Status of the Nation's Highways, Bridges, and Transit: Conditions & Performance, a Congressionally-mandated document that reports on the effects of past Federal surface transportation funding and authorization bills and informed future bills related to the surface transportation program.(7) NHTS data were also used in a series of reports produced by The National Surface Transportation Policy and Revenue Study Commission, created by Congress in 2005 under the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU), to inform future reauthorizations.(8)

Other NHTS uses related to legislation involve advocacy groups and non-profit organizations. For example, the American Association of Retired People (AARP) and the American Association of Automobiles Foundation for Traffic Safety (AAAFTS), often use NHTS data in their reports and presentations to increase awareness about priority topics and to lobby Congress for action. Furthermore, with respect to regulatory uses, NHTS data are integral to the calculation of the model year Corporate Average Fuel Economy (CAFE) standards, which are regulations issued by the National Highway Traffic Safety Administration.(9–10)

In addition, NHTS informs policy and initiatives in other fields, including health and energy. Data on bicycling and walking have been used by the Centers for Disease Control (CDC) in its 10-year agenda, Healthy People 2020 and most recently in the Step it Up! The Surgeon General's Call to Action to Promote Walking and Walkable Communities.(11–12) The Energy Information Administration (EIA) relies on NHTS derived vehicle miles traveled (VMT) and household vehicle data, combined with other data from the EIA and the Environmental Protection Agency (EPA)[2] to derive vehicle fuel consumption and vehicle fuel expenditures. These statistics are used extensively by policy and decisionmakers to understand economic and environmental impacts of changing travel demand.

States and MPOs use the data for a range of purposes. In most cases, NHTS trip data are used to develop, calibrate, or validate State and MPO travel demand models.[3] Interviewees indicated that these models are critical to transportation planning and inform corridor level, interchange, and transit projects, among others. In addition, States and MPOs that are required to produce air quality reports (because of their status as a non-attainment area) use NHTS data as an input to their models.

NHTS Responsiveness to its User Community

The Volpe qualitative analysis found that NHTS engages with its user community using a variety of methods. Most notably, in 2011, NHTS organized the NHTS task force to solicit input from the user community. Based on its research, the NHTS task force presented NHTS with user feedback on suggested updates to the NHTS methodology and survey content, and a number of these suggestions are being implemented in the 2016 NHTS survey. In addition, NHTS convened two meetings of an expert review panel to provide technical guidance on the redesign of the upcoming survey.

Other methods by which the NHTS Program interacts with users include providing direct user support via the NHTS website (e.g., NHTS User Guides and FAQs) and responding to requests by phone and email.(13-14) The NHTS Program has conducted a number of formal outreach activities to gather input from its users, including TRB sessions and committee updates, as well as workshops and conferences. Based in part on user feedback, NHTS has introduced more online tools, such as NHTS Academy modules and online analysis tools.

Challenges and Lessons Learned

A key challenge expressed by some FHWA staff is a lack of secure and sufficient funding for the NHTS survey; this makes it difficult to plan for the survey in advance. Minimal staffing makes it difficult to conduct outreach. Another challenge is that NHTS does not have the resources to maximize use of the data within the program by conducting indepth analyses and publishing results under the FHWA/NHTS name. NHTS has to rely on the user community to use the data and publish results, so “often the connection between the data being cited and its source in the NHTS datasets is lost in translation.”[4]

From the user perspective, lack of institutionalized funding signals that the NHTS Program is a lower priority program. Add-ons are reluctant to come on board without secure funding. In addition, users feel that the NHTS could be more effective and attract a greater audience if it were conducted on a regular cycle and with greater frequency (3–5 years). They acknowledge that such changes would require more staffing resources and stable funding.


The challenges and lessons learned described by interviewees provide the basis for key recommendations regarding the NHTS Program. Most importantly, NHTS requires a stable source of funding, with surveys that are conducted on a regular cycle, so that users know when to expect the data and can plan accordingly. NHTS would benefit from greater outreach, particularly with Congressional policy staff, but this would require an increase in the number of NHTS staff, as the current staff is stretched very thin.

In terms of tracking its data usage and impact, NHTS must continue to emphasize the importance of (1) citing NHTS when it is used and (2) encouraging users within DOT and other agencies to send the program any reports, publications, and/or models that use NHTS. While the NHTS should continue to track publications in its Compendium of Uses Compendium of Uses*, this tends to represent academic research and reports, so additional efforts are needed to track usage by Federal, State, and local government. Media requests and requests from Government officials should be tracked by FHWA’s Public Relations Office in an accessible format (e.g., Microsoft® Excel) so that this information can be easily retrieved and summarized to provide evidence of NHTS impacts.

*Revised 4/18/2018


Although Volpe identified many cases where the NHTS is used in the development of transportation-related reports, presentations, calculations, and models, it was difficult to trace specific impacts of NHTS data. Nonetheless, it was clear from the interviews and identified examples that NHTS data inform a range of policy and legislative decisions, both within transportation, as well as in other fields, such as health and energy. In some cases, NHTS provides context and understanding for how, when, and why Americans travel; trends in travel; and differences in travel by key subgroups. This context helps make the case for particular policy or legislative initiatives. In other cases, NHTS is an important data input to a model or statistical analysis, which is used in turn to influence policy or legislation. At the State and local levels, Volpe found that NHTS has its greatest impact in developing, calibrating, or validating travel demand models that are used to inform transportation planning and project selection.

1 Website statistics are available from internal FHWA reporting systems.

2 Refer to section Use of NHTS in Policymaking in nontransportation Fields.

3 Refer to section State and Local Transportation Policy and Planning.

4 Former FHWA staff, email correspondence, September 2015.



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