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

3. Evaluation Findings

This chapter presents evaluation findings for each of the four key impact areas, summarizing findings for each of the key performance metrics.

3.1   Breadth and Depth of NHTS Usage

Findings on the breadth and depth of NHTS usage were explored using NHTS website statistics as well as an analysis of the Compendium of uses documents compiled by the NHTS Program.

3.1.1 Website Usage Statistics

An analysis of monthly website usage data from July 2013 to May 2015 provides insights on the magnitude of use of NHTS tools and outputs as well as patterns of usage. Key questions included the following:

• To what extent do researchers visit the NHTS website to access information?
  
  
• To what extent do researchers download NHTS datasets and user guidance documents and information?
  
  
• To what extent do researchers use the online analysis tools?
  
  
• To what extent do researchers download publications?

A key limitation of the analysis is that we do not know the extent to which new visitors, versus repeat visitors, are accessing the site and its components on a monthly basis.

The analysis of website usage statistics reveals robust website usage and an overall cyclical trend in how the NHTS data and outputs are used, with peaks generally in the early fall and spring each year and diminished use in the summer and winter months. In the period studied, July 2013 to May 2015, monthly visitors ranged from a low of 2,700 to a high of 4,949. Monthly visits also varied month to month, ranging from 4,545 visits in the slowest month to more than 9,340 in in the busiest, with an average of 1.7 visits per visitor. The range in usage stems from both the cyclical usage trend as well as a period of increased usage starting in August 2014. Despite the fact that six years have passed since the release of NHTS data, users continue to visit the website.

These data also suggest that users are accessing different outputs and tools on the NHTS website. The NHTS Publications section tended to be the most accessed portion of the website, which speaks to the value of this Publication among users. The online Table Designer is another frequently used tool, although it shows wide usage swings. Materials supporting the raw NHTS data including the 2009 NHTS Datasets, Codebooks and User Guides⁽¹⁹⁾are downloaded by a smaller set of users. The Online Codebook page, however, did see a higher number of activations.

The following sections provide detailed findings, supported by charts and graphs.

3.1.1.1 Website Traffic

Website traffic, shown in Figure 2, conveys an increase in visits during the second half of the period studied. Monthly visitors ranged from 2,757 to 3,686 for the 12-month period (July 2013–June 2014) with visits ranging from 4,535 to 6,176 monthly. Starting in August 2014, usage increased significantly, ranging from 2,700 monthly visitors (4,825 monthly visits) to 4,949 visitors (9,340 visits) in the spring. Over this short period of time, a trend of increased monthly visits is evident, even as visits ebb and flow through the seasonal usage cycle.

Figure 2. NHTS website traffic, July 2013–May 2015.

 

Homepage view of Online Tools and Publications (Figure 3) follow the same cyclical trend as the website traffic but do not show dramatic usage increases. Online Tools received 900–1,600 homepage views per month, while views of the publications homepage were 1,000–1,600. Frequently Asked-For Tables shows only a weak cyclical trend, with relatively flat usage in July 2013–June 2014 (roughly 450–700 homepage views monthly). There was a surge in views during the peak periods of fall 2014 and spring 2015, with more than 900 views in both September 2014 and April 2015. This tracks with the increased number of visits seen on the overall website during this time.

Figure 3. NHTS website tool homepage views, July 2013–May 2015.

 

3.1.1.2 Datasets and Guidance Documents

The NHTS data related outputs such as the 2009 Codebook and 2009 Dataset are used by a much smaller set of NHTS users (Figure 4). The 2009 Codebook was downloaded only 114–333 times per month, while the 2009 dataset was downloaded slightly more often (roughly 200–500 times per month). The 2001 Dataset showed even lower usage, ranging from 25–100 downloads per month. Both 2009 Codebook downloads and 2009 Dataset downloads seem to benefit from the increase in visits and visitors after August 2014. User Guides (not shown) tend to have similar usage levels, ranging from 250–500 downloads per month, with again a slight increase starting in the fall of 2014.

Figure 4. NHTS website dataset and codebook downloads, July 2013–May 2015.

 

3.1.1.3 Tool Activations

Of the number of online analysis tool activations, the Table Designer Tabulation had the most usage as well as the most volatility, with fall and spring peaks proportionally much larger than that of the other online analysis tools (see Figure 5). This tool sees spikes of heavy usage in peak periods, with usage levels ranging from under 900 activations per month in slower times to close to 6,000 per month at peak. It is interesting to note that usage seems to increase starting in August of 2014, which tracks with overall increases in visits and visitors, but Volpe did not see increased homepage views for the Online Tools homepage. It is possible that repeat users are linking directly to the Table Designer tool.

The Codebook tool gets three to five times more activations than its downloadable counterpart (see Figure 4), ranging from 350–1,900 activations per month. This tool shows a weak yearly cycle, with more pronounced usage peaks in the spring. This tool does not seem to be affected by the increase in visits during the second half of the analysis period. The Data Extraction Tool, with the lowest activations, does not seem to be very affected by the increase.

Figure 5. NHTS website online tool activations, July 2013–May 2015.

 

3.1.1.4 Publication Downloads

Publications tends to be one of the most accessed areas of the NHTS website. The summary measure Total PDFs Viewed includes the 2001 and 2009 Summaries of Travel Trends (also broken out individually), as well as the compendiums and briefs, journal articles, reports, and presentations that are provided by the NHTS website. Publications viewed doesn’t seem to follow the cyclical trend as closely as other NHTS products (Figure 6). It does, however, show that it has been influenced by the increased number of visits and visitors, as usage climbs through the analysis period. Total PDFs Viewed ranges from a low of 5,253 (in August 2013) to a high of 13,713 (in October of 2014), with views leveling off to about 12,000 in May 2015. The 2009 Summaries of Travel Trends sees a similar trend of increased views, ranging from a low of 1,682 views per month to a high of 5,132, making it one of the most accessed NHTS outputs. Downloads of the 2001 document are relatively stable (with the exception of August 2014), as predictably, it is downloaded much less frequently than the 2009 document.

Figure 6. NHTS website publication downloads/views, July 2013–May 2015.

 

3.1.2 Compendium Analysis

To inform the evaluation of the breadth and depth of NHTS data use, Volpe analyzed in depth the NHTS Compendium of Uses NTHS Compendium of Uses*⁽¹⁾ and compared summary data from the 2011–2013 compendiums^(3,4) to understand how the topics and themes have changed or evolved throughout time. Key questions included the following:

• To what extent are NHTS data used across a range of fields?
  
  
• To what extent are NHTS data used across a range of transportation related topics?
  
  
• To what extent does NHTS serve a range of user types including Federal staff, States/MPOs, and academics?

*Revised 4/18/2018

3.1.2.1 Transportation Fields and Topics

Almost half of the publications (46 percent) in the Compendium share the primary field of transportation, as illustrated in Figure 7. This is not surprising for a dataset with a primary focus on household travel. However, it is interesting that more than half of the publications have primary applications in other fields. After transportation, energy consumption is the next most popular field at 25 percent, followed by survey methods and data analysis at 12 percent, environment at 9 percent, and health at 8 percent. These data indicate that the NHTS is being used across a range of fields and that the data have utility beyond transportation.

Health emerged as a field worth highlighting and included several transportation topics: bike and pedestrian issues, travel characteristics and behavior, and, most notably, policy and mobility (Table 4). Publications, including the policy and mobility topic, had a strong focus on public health issues (e.g., physical activity correlation with obesity and cancer, health benefits of land use and transportation plans, and neighborhood parks and adolescent stress reduction, etc.).

Figure 7. 2014 NHTS compendium primary fields.

 

A range of transportation topics were covered within each field, as shown in Table 5. The topic travel characteristics and behavior is seen regularly across fields. The policy and mobility and demographics and travel trends topics are also covered to some extent in all fields. Innovative technologies dominates the energy consumption field (94 percent) and also has applicability to survey methods (34 percent) and to a lesser degree environment (24 percent) and transportation (15 percent) publications. Other topics such as bike and pedestrian, special populations, and traffic safety tend to fall within the transportation and health fields.

Looking specifically at the distribution of transportation topics within the transportation field (column 2 of Table 5), the data show that travel characteristics and behavior (62 percent) and policy and mobility (56 percent) are the leading topics covered by the Compendium publications, followed by demographics and travel trends (36 percent). Bike and pedestrian and special populations are covered by one-fifth of the publications. More specialized topics such as transit planning, innovative technologies, and traffic safety are seen less frequently.

Table 5. Transportation topics by field.

	Transportation	Energy	Survey Methods & Data Analysis	Environment	Health
Travel Characteristics & Behavior	62%	35%	58%	28%	50%
Policy & Mobility	56%	15%	42%	76%	58%
Demographics & Travel Trends	36%	14%	21%	38%	38%
Bike & Pedestrian	21%	0%	8%	0%	38%
Special Populations	19%	1%	0%	0%	21%
Traffic Safety	16%	0%	0%	0%	13%
Innovative Technologies	15%	94%	34%	24%	0%
Transit Planning	12%	4%	3%	7%	8%
Note: Because multiple topics could be checked for each field, the percentages sum to more than 100%.

 

Figure 8 illustrates the distribution of transportation topics (within the transportation field) classified as either primary or secondary (e.g., a publication’s primary topic is Transit Planning, but also relates to, or has secondary topics of, Bike and Pedestrian and Demographics and Travel Trends). Travel Characteristics and Behavior and Policy and Mobility are cited frequently as both primary and secondary topics. Demographics and Travel Trends are more likely to be secondary topics within the Transportation field. The dominance of these three categories in Table 4 is further explained here. These subjects have wide applicability to other topic areas and therefore overlap with a greater number of Compendium topics. Other topic areas (e.g., Bike and Pedestrian, Traffic Safety, and Transit Planning) tend to be more focused, and hence have a greater distribution of primary, compared to secondary, classifications. These data demonstrate that the value of the NHTS is both its wide range of topics covered and also the value of the interaction of these categories to explain both general and specific topics related to transportation.

Figure 8. Transportation topics summary, primary vs. secondary (within transportation field).

 

While Volpe was not able to analyze each Compendium to the scale conducted for 2014, a high-level analysis was performed to look at how transportation topics may have shifted throughout time. As illustrated in Figure 9, the 11 original NHTS categories were compared across the 3 latest Compendiums (2011–14) to see if any shifts in topic focus could be identified.^[7]

While the frequency of some topics remained unchanged (e.g., bike and pedestrian), others have shifted fairly dramatically (e.g., travel characteristics and behavior, demographic trends). For these two categories, it is possible that the content of the publications has not changed as much as the classification of the publications (because of overlap with other topics). As seen in figure 9, travel characteristics and behavior is a topic that often co-exists with one or more other topics in NHTS-related publications, such as demographics and travel trends. Other topics that show some increase include energy consumption and survey methods and data analysis.

Figure 9. 2012–2014 NHTS compendium original classification summaries.^[8]

 

The increased citations for energy consumption and survey methods and data analysis are further demonstrated in figure 10, which divides publications into Transportation or Non-Transportation categories. The data shows that NHTS is growing its reach to other fields outside of Transportation (i.e., Energy, Environment, and Survey Methods and Data Analysis), illustrating the value that this dataset provides beyond transportation.

Figure 10. 2012–2014 NHTS compendium original classification summaries.^[9]

 

In addition, data from the Compendium was used to provide a snapshot of user types and applications. Figure 11 presents a summary of NHTS use classified by whether the focus of the publication was national, State/MPO or international. Nearly half of publications (45 percent) are related to research topics with impacts at the Federal or national level, 30 percent are related to work with an international focus, and State or MPO/Regional research followed closely at 25 percent. While the international emphasis was surprising, it seems that NHTS data were used in these cases to compare travel trends, behaviors, or survey methodologies with geographic areas outside of the United States. These data illustrate that the NHTS has utility across multiple spheres, providing information on topics that are national as well as local in scope and enabling decisionmakers to understand U.S. travel behavior as it compares to travel in other countries.

Figure 11. 2014 NHTS compendium publications by application.

 

3.1.2.2 Range of Users Analysis

The vast majority of publications captured in the 2014 Compendium⁽¹⁾ (82 percent) are written by academics or by those in organizations associated with universities. Eighteen percent of these tend to be students working on undergraduate, Masters, or Doctoral theses. Very few of the 300+ publications come from government employees (Federal, State, or local), transportation consultants, or those in industry or media. Although the percentage of academics seems high, the analysis does not account for the fact that the academic organization may be doing research for or with the government or for the private sector. In addition, academics are more likely to publish their findings; thus these sources are more likely to be captured by the compendium.

Figure 12. 2014 compendium lead author by organization type.

 

The lead presenters at NHTS-sponsored conferences, workshops, or TRB sessions represent a wider mix of NHTS users than does the 2014 Compendium⁽¹⁾ (see figure 13). Only 41 percent of presenters come from academic or university-related organizations, while 27 percent are from different areas of the Federal Government (USDOT and other organizations). Transportation consultants who work with the NHTS also make up a large portion of presenters (22 percent). State and regional governments and nonprofits make up a smaller share of presenters.

Figure 13. NHTS conference/workshop lead presenters by organization type.

 

It should be noted that the data presented in figure 12 and figure 13 (compendium lead authors and lead presenters) is not generalizable, nor is it representative of all users; rather, it provides a snapshot of users based on two distinct data sources. As noted previously in the Methodology section, NHTS users do not always publish their work, and in some cases, users do not cite the NHTS directly, so it is not possible to develop a complete listing of all NHTS uses and users.

3.2   NHTS Impact on Policy, Project, or Regulatory Decisionmaking

The logic model developed for this evaluation proposes that the NHTS creates long-term impact by informing decisionmaking in the areas of policy, projects, and rulemaking. These policy, project, and rulemaking decisions occur at the local, State, and Federal levels of government. This examination of the NHTS impact on decisionmaking focused on four evaluation questions:

1. To what extent and in what way does NHTS data inform transportation policy decisions and rulemaking?
   
   
2. To what extent and in what way does NHTS data inform non-transportation related policy decisions and rulemaking?
   
   
3. To what extent does NHTS impact transportation project selection and/or lead to project modification?
   
   
4. To what extent does NHTS impact non-transportation project selection and/or lead to project modification?

Although Volpe identified many cases where the NHTS is used in the development of transportation-related reports, presentations, calculations, and models, there were few formal documents detailing how NHTS data or findings fed directly into policy, project, and rulemaking decisions. Policy and decisionmaking proceedings are not always transcribed and even those that are often fail to attribute discussions of travel behavior to the NHTS. In addition, the products of such proceedings (legislation, testimony, and project approval) often fail to directly credit the NHTS, as it is one information source of many. In addition, policy and program decisions do not hinge on any single data source. As one interviewee noted:

“NHTS is one of many sources that informs policy, project, and regulatory decisions. It would not likely be a driver of any decision but instead a contributor to many.”^[10]

Another interviewee noted that it is difficult to trace NHTS use because transportation policymaking tends to be decentralized.

“Transportation policy is thought of as a State/local issue. Policymaking and funding is much more diffuse more diffuse*, compared to other agencies.”^[11]

*Revised 4/18/2018

Interviews with NHTS Program staff, FHWA staff, and lead users proved more successful as many anecdotes were provided describing how NHTS was used as a source of information for policy, project, and regulatory decisions.

This evaluation topic is organized according to the following three subtopics:

• NHTS Use for Federal Transportation Policy and Rulemaking (3.2.1)
  
  
• NHTS Use for Policymaking in Nontransportation Fields (3.2.2)
  
  
• State and Local Use of NHTS Data for Planning, Policy, and Project Selection (3.3.3)

3.2.1 NHTS Use for Federal Transportation Policy and Rulemaking

Across all the interviews, NHTS Program Managers and lead users reported that the NHTS provides critical information to the Federal government for the purpose of understanding the current travel environment, examining trends in travel behaviors, and examining transportation issues in key sub-populations. One lead user commented that:

“Travel behavior is very complex … [NHTS] builds a mosaic of understanding and provides context, based on data; evidence can ripple through the system and have an effect. [NHTS] informs conversation about important topics.”^[12]

The NHTS is the only source of data to provide a comprehensive picture of all travel for the entire U.S. population. This information provides the foundation on which transportation policy and funding legislation are built. As described by one interviewee:

“[Policymakers] need representative data to give them a solid foundation in which to evaluate the present and the needs of the future. [NHTS] impact is not explicit… it gives the broad context …”^[13]

Several NHTS outputs serve this role, providing important information on trends in travel and findings on key travel-related topics. The NHTS Summary of Travel Trends,⁽⁵⁾ for example, is the primary compilation of NHTS findings. This document is developed by NHTS staff using data from current and previous NHTS cycles. It highlights travel trends and commuting patterns in eight areas: travel and demographics, household travel, person travel, private vehicle travel, vehicle availability and usage, commute travel patterns, temporal distribution, and special populations. This document is available to users within and outside the Federal Government through the NHTS website⁽¹⁶⁾ and is cited by countless other transportation-related research and reports, including those detailed below (e.g., C&P Report, Beyond Traffic Report, and Commuting in America).⁽⁶⁾

The NHTS Policy Briefs, also developed by NHTS staff, use NHTS data to address a relevant transportation topic. The topics are selected based on what the NHTS team hears while attending OST planning sessions or TRB conferences, listening to user feedback, or noting current trends in the media. These documents provide a deep dive into one transportation topic of social or legislative importance and are available via the NHTS website. Policy Brief topics have included Mobility Challenges for Households in Poverty,⁽²⁰⁾ Changes in the US Household Vehicle Fleet,⁽²¹⁾ and Active Travel,⁽²²⁾ among other topics. The NHTS Policy Briefs feed directly into policy discussions within transportation and other fields; they also inform reports, such as former Secretary of Transportation Anthony Foxx’s Beyond Traffic Report,⁽⁶⁾ which is described in more detail in the next section.

3.2.1.1 NHTS Use in DOT Reports and Initiatives

NHTS data are incorporated in DOT Reports that are widely circulated within and outside of the Federal Government and are used to inform both policy and legislation. One notable example is the Beyond Traffic Report,⁽⁶⁾ issued by former Secretary of Transportation Foxx. In the Trends chapter, NHTS Summary of Travel Trends findings contribute to the discussion of the changing travel behavior of millennials and older Americans. The NHTS Income Inequality Brief⁽²⁰⁾ was used to develop a section that focused on income inequality and the financial burden that transportation puts on working class families. Other chapters cite the use of the travel trends document as a source of information on why people travel, how much they travel, and the mode of transportation used, including a section on biking and pedestrians.

While it is too early to determine the type of impact that the Beyond Traffic Report⁽⁶⁾ will have on policy and legislation, this document serves as a resource to inform the conversation between transportation users, operators, and providers and the legislators and policymakers who shape the transportation landscape. This document reports on the current and predicted future conditions of our transportation system, enabling discussion on what our country needs to do to support our transportation system and why it needs to be done. The report is still a draft but has already been distributed extensively to members of Congress and State and local elected officials. In addition, the report has already been downloaded more than 370,000 times (as of 8/12/15).

The Safer People, Safer Streets: Pedestrian and Bicycle Safety Initiative⁽²³⁾ by former Secretary of Transportation Foxx, which addresses nonmotorized safety issues in communities, provides another example of how NHTS data inform the policy conversation. Data from the 2001 and 2009 NHTS are used to understand the national use of biking and walking for daily travel. More specifically, NHTS provides information on walking and bicycling trips in relation to other travel modes and within important sub-populations such as millennials. This contextual information helps frame the scope of the issue and identifies key subgroups that may need to be targeted.

In addition, the National Center for Safe Routes to School (SRTS) has used NHTS to look at trends in walking and bicycling to school. The National Center for SRTS was established in 2006 through FHWA funding and serves as the clearinghouse for the Federal SRTS Program. In 2010, the National Center for SRTS issued a press release, U.S. Travel Data Show Decline in Walking And Bicycling To School Has Stabilized⁽²⁴⁾ that relied on findings from the 2009 NHTS.

3.2.1.2 NHTS Use for Legislative and Regulatory Purposes

NHTS data are also incorporated into Congressionally-mandated reports to inform reauthorization legislation or continuing resolutions for the surface transportation program. In this role, NHTS data are explicitly serving a legislative purpose. In the Status of the Nation’s Highways, Bridges and Transit: Conditions and Performance Report to Congress (C&P Report),⁽⁷⁾ for example, the NHTS is both a direct and indirect information source. This Congressionally-mandated report addresses the effects of past federal surface transportation funding and authorization bills. It is distributed to Congress and notably used in three Senate committees and one House committee. Through this document, NHTS is providing lawmakers with critical information on which to base future decisions regarding transportation in the U.S.

The first chapter of the report, “Household Travel,” was written by the NHTS Program manager and presents the landscape of household travel in the U.S, including travel trends in the context of demographics, location, and overall changes in travel, such as declining vehicle miles traveled (VMT). The report also includes a discussion of NHTS findings with important policy implications, such as mobility issues for aging baby boomers and changes in travel behavior of the millennial generation. Other NHTS-related topics include changes in the household vehicle fleet, biking and pedestrian issues, transit, and an instructive discussion on potential NHTS inputs to land use planning and travel demand forecasting (e.g., trip rates, trip lengths, and trip purposes and characteristics). Indirect usage of the NHTS is also present throughout the C&P Report through models and calculations that use NHTS inputs. These models provide critical information used to determine levels of transportation funding, emissions standards, and fuel economy standards and are described in more detail in sections that follow.

NHTS data were also used in the Transportation for Tomorrow: Report of the National Surface Transportation Policy and Revenue Study Commission,⁽⁸⁾ commissioned by Congress under the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) to examine the condition and future needs of the nation's surface transportation system and to assess alternative short- and long-term revenue sources for the Highway Trust Fund. The report was used by Congress as it considered reauthorization of SAFETEA-LU in 2009. The 2001 NHTS is represented in the Transportation for Tomorrow Report⁽⁹⁾ as a primary data source used for seven briefing papers focused on informing the committee of the impact of demographic changes on passenger travel (Table 6). While Volpe cannot explicitly point to the impacts of these Reports on reauthorization, it is clear that these data were critical to understanding the transportation landscape and at a minimum served to inform legislators about key trends and issues in U.S. travel behavior.

Table 6. Commission briefing papers using NHTS data.

No.	Title	Description
1	Analysis of Changing Relationships Among Population Growth, Passenger Travel Growth, and Vehicle Miles Traveled Growth for Different Modes(25)	Examination of current travel behavior and trends in the context of demographic factors to make predictions about future behavior.
2	Implication of Aging Population on Passenger Travel Demand for Different Modes(26)	Future transportation implications of an aging population. Projections of number of older drivers, vehicle miles traveled (VMT), pedestrian and traffic accidents, aging vehicle fleet, and suburban transportation needs.
3	Implication of Alternative Assumptions Concerning Future Immigration on Travel Demand for Different Modes(27)	Implications of future immigration on travel demand as new immigrants exhibit different travel behaviors in terms of mode used (e.g., transit, pedestrian, and carpool).
4	Implications of Regional Migration on Passenger Travel Demand(28)	Implications on travel demand (VMT) based on future migration. South and West may see a disproportionate increase because of migration while other regions will level off or decline.
5	Implications of Rural/Urban Development Patterns on Passenger Travel Demand(29)	Implications of population growth and distribution of the population (and jobs) among major cities, suburbs, and rural areas. Impact of growth on travel demand and related services.
6	Implications of Rising Household Income on Passenger Travel Demand(30)	Examination of historical patterns, income, and related travel, considering that rising income may not affect travel as strongly in the future.
7	Implications of Work and Nonwork Travel Patterns on Passenger Travel Demand(31)	Implications of the expected growth of nonwork travel relative to work travel and the impact on travel speed and other factors.

 

A leading transportation consultant interviewed for this evaluation described several cases where NHTS findings were delivered directly to transportation-focused Congressional committees through testimony. As Congress prepared for reauthorization of SAFETEA-LU, the consultant was invited to provide the committee with an overview of U.S. travel trends and patterns. The transportation consultant gave testimony prior to advocacy groups, so that the committee would have the appropriate context in which to frame what they would later hear from the advocacy groups. His testimony was based directly on NHTS findings. As the consultant explained:

“Without NHTS you are naked...you don't know what is going on with American travel behavior.”^[14]

Other examples of Congressional testimony that reference NHTS include the following:

• Testimony before the U.S. House of Representatives Committee on Transportation and Infrastructure Sub-Committee on Highways and Transit: Highway Trust Fund Viability 2007.⁽³²⁾
  
  
• Testimony before the U.S. House of Representatives Committee on Appropriations Sub-committee on Transportation, Housing, and Urban Development and Related Agencies: Transportation and Housing Linkages 2007.⁽³³⁾

NHTS data are also used as an input to a key model that provides information (VM-1 Table) used to determine levels of transportation funding. More specifically, NHTS data on vehicle occupancy, in combination with Highway Performance Monitoring System (HPMS) data, fuel consumptions data, vehicle registration data, and data from other sources are used to develop vehicle miles traveled (VMT) calculations. This measure of VMT is key for highway planning and management and a common measure of roadway use. Along with other data, VMT is used in estimating potential gas-tax revenues through the Highway Trust Fund, as well as congestion and air quality.

With respect to regulatory uses, NHTS inputs are also integral to the calculation of the model year Corporate Average Fuel Economy (CAFÉ CAFE*) standards⁽¹⁰⁾ and are used specifically to provide forecasts of personal VMT and to provide information on the household vehicle fleet (e.g., type, age, and vehicle occupancy). By contributing to the development of these regulations, NHTS data plays an important role. All vehicle manufacturers must comply with the CAFÉ standards,^[15] which serve to reduce energy consumption by increasing the fuel economy of cars and light trucks. In 2012, the White House highlighted the new standards that were issued, the significance of which was expressed by President Obama: “These fuel standards represent the single most important step we’ve ever taken to reduce our dependence on foreign oil.”

*Revised 4/18/2018

3.2.1.3 Advocacy Groups and Nonprofits

In addition to its use by government agencies, NHTS is widely used by consultants and organizations outside of government. Nonprofits and advocacy groups, for example, use the NHTS to educate the public, inform decisionmakers, and to advocate for their legislative and policy agendas. This section highlights some of the research being conducted by the American Association of State Highway and Transportation Officials (AASHTO), American Automobile Association Traffic Safety Foundation (AAATFS), and the American Association of Retired People (AARP).

AASHTO, a nonprofit, nonpartisan association representing State highway and transportation departments, has used NHTS data in its Commuting in America report, a series of briefs that describe commuting patterns and trends in the U.S. While the primary data source for this report is the American Community Survey, NHTS data are added to provide information on how work-related travel fits in with the rest of daily travel, presenting a more complete picture of commuting. As one interviewee explained:

“NHTS data needs to be used to give strength to the Census data; the two complement each other–one is fat where the other is thin.”^[16]

Commuting in America is distributed to every member of Congress and their staff, and all State Secretaries of Transportation and their staff for use in transportation-related decisions.

Another nonprofit, AAAFTS, which conducts research to address growing highway safety issues, also has relied on NHTS data to shed light on risks associated with driving. More specifically, these analyses used NHTS data on number of miles driven, number of trips, demographic characteristics (age and gender), and vehicle occupancy. Two research projects are summarized in Table 7.

Table 7. AAAFTS project examples using NHTS data.

Document	Description
Teen Driver Risk in Relation to Age and Number of Passengers(34)	Provide a measure of exposure to risk (e.g., miles driven) among different subgroups by computing crash rates per mile in relation to age/gender. Quantify teenage drivers' relative risk of crash involvement per mile driven in relation to the presence, number, and age of passengers in the vehicle.
Risks Older Drivers Pose to Themselves and Other Road Users(35)	Explore the risks that drivers pose to themselves and to others (e.g., passengers or occupants of other vehicles) on a per-driver, per-trip, and per-mile basis.

 

As an input to these risk analyses, NHTS data serve an important role. Through providing a more detailed understanding of the risks associated with teen and older drivers, this research helps identify the nature of the risk among different population subgroups, and these results can be used to develop specific polices or laws that will mitigate those risks.

The AARP also has used the NHTS extensively as a source of information for research on transportation issues affecting older Americans. The AARP even purchased an Add-on sample from the 2009 NHTS to have more robust data on this topic. Table 8 lists several examples of research sourcing NHTS data. This research contributes to a better understanding of the transportation needs of older Americans and policies or laws that may be needed to support this population.

Table 8. AARP project examples using NHTS data.

Document	Description
Transportation Funding Reform: Equity Considerations for Older Americans(36)	Presents the case for the government to expand, improve, and enhance a wide range of transportation facilities and services that meet the needs of older people.
Aging in Plac3 Place*(37)	Compares the U.S. to other countries on those age 65+ in America traveling by foot or bicycle.
Impact of Baby Boomers on U.S. Travel, 1969 to 2009(38)	Discusses the impact aging Baby Boomers having on travel, including declining vehicle miles traveled.
T 4 America. Dangerous by Design, Study without Options(39)	Issues and impacts of the largest number of Americans 65+ living in the suburbs.

*Revised 4/18/2018

Recently the AARP’s Government Relations and Advocacy group supported the passage of a Livable Communities Act to coordinate policies and investments to develop communities that accommodate the housing and transportation needs of older persons. In a letter to the Senate Committee urging passage of the Livable Communities Act, AARP referenced the 2009 NHTS, providing data on the percentage of seniors who drive. In addition, NHTS inputs on walking trips have been used to develop the AARPs Livability Index, an online tool that assesses seven broad categories of community livability: housing, neighborhood, transportation, environment, health, engagement, and opportunity. The Livability Index helps users better understand their communities and make decisions about future needs.

3.2.1.4 Technology and Policy Innovation

As described in this previous evaluation topic, the breadth and depth of NHTS Use, academics and consultants use the NHTS data to address a wide range of questions. These research topics are often directly linked to policy initiatives and are useful in providing context or understanding. This can be particularly important for research on innovative technologies.

Research being conducted at the University of Michigan, for example, used NHTS data to explore the impacts of self-driving vehicles on vehicle ownership.⁽⁴⁰⁾ The researchers found the potential for reduced vehicle ownership within households based on sharing of completely self-driving vehicles that employ a “return-to home” mode. As the DOT continues to focus on Automation,^[17] NHTS enables research that contributes to our understanding of what to expect in a world of self-driving vehicles, and it provides decisionmakers with important information on which to base future policies in this area.

In addition, there has been a significant growth in the use of NHTS data to explore issues related to electric vehicles. Papers cover a variety of topics within this area, including 1) the design and performance of charging facilities, as well as their impact on land use decisions;⁽⁴¹⁾ 2) charging technology, including storage (e.g., fuel cells and batteries) and use of renewable energy;⁽⁴²⁾ and 3) understanding electric vehicle feasibility and needed improvements to meet forecasted demand.⁽⁴³⁾ With DOT’s growing emphasis on sustainability, and with policy initiatives such as the Department of Energy’s SmartGrid, this research plays an important role in informing the national conversation on electric vehicles and their feasibility.

3.2.1.5 Use of NHTS in the Media

The media, as well as public and private sector journals, have covered a range of issues that highlight NHTS findings, including the growth of biking and walking, changes in commuting patterns, shopping patterns, and transit use, and more recently, the impact of self-driving vehicles on vehicle ownership. The media outlets covering these stories reach a national audience and include USA Today,⁽⁴⁴⁾ Bloomberg News,⁽⁴⁵⁾ The New York Times,⁽⁴⁶⁾ The Washington Post,⁽⁴⁷⁾ Atlanta Journal Constitution,⁽⁴⁸⁾ The Denver Post,⁽⁴⁹⁾ and St Louis Post Dispatch⁽⁵⁰⁾ to name a few. NHTS data findings are reported by foreign media outlets.

The media can serve as another channel through which NHTS findings make their way to decisionmakers, and these stories can help to set the agenda, calling attention to certain issues or topics. The FHWA Public Relations Office receives two to three requests for information per week, on average, from the media. As the Public Relations Officer explained:

“Of the many data sources made available to the public by the FHWA, the National Household Travel Survey is among the most highly requested by reporters writing about changes in America’s transportation habits–from the rise of elderly drivers, to the growth of multiple, short trips (compared to longer “trip-chaining” trips), to the rise of bike riding and walking, to the decline of teens seeking their driver’s licenses at 16. The data run the gamut, which explains their utility to news reporters.”^[18]

3.2.2 Use of NHTS in Policymaking in Nontransportation Fields

Several Federal agencies including the Energy Information Administration (EIA) and Environmental Protection Agency (EPA) use data from the NHTS as inputs to models and in the calculation of policy-related statistics. These sources provide information to policy and decisionmakers that impact energy and environmental policy. Models may also be used at State or region levels to provide information in compliance with Federal and State regulations. Other agencies such as the Centers for Disease Control (CDC) use findings that are solely available in the NHTS to inform health initiatives, which in turn facilitate the development of health-related programs.

The EIA uses NHTS data to calculate energy-related statistics and has used these data in a number of its reports, including its Annual Energy Outlook. NHTS-derived VMT and household vehicle data are combined with data from the EIA and EPA on fuel economy and fuel price 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. For example, EIA uses these data to respond to specific requests from members of Congress to assess the impacts of proposed energy legislation.

EPA uses NHTS data, specifically VMT, number of vehicles, and fleet information (e.g., age) to develop default model data that can be used in its Motor Vehicle Emissions Simulator (MOVES),⁽⁵¹⁾ an emission-modeling system that estimates emissions for mobile sources. While agencies are expected to upload their own data to the model in order to customize the results to their specific geographic area, this default data can be used in cases where States or regions do not collect their own data. States are required to provide EPA with emissions data as part of their State Implementation Plan, and MPOs in nonattainment areas must report on emissions to ensure the region is meeting conformity and air quality goals. In this way, NHTS data are helping States and MPOs meet their reporting and planning requirements.

In the health arena, NHTS data on walking and bicycling are used to spotlight the importance of physical activity to good health. A CDC official expressed the importance of the NHTS data as follows:

“The NHTS travel diary is unique in that it provides trip data by mode, length, and purpose—unlike any national health survey. For public health, this data allows a more detailed analysis of travel behavior, especially of active transportation (walking, bicycling, and, by some definitions, transit use) which, in turn, is known to be associated with an active and healthy life.”^[19]

Table 9 presents several key examples of the use or potential use of NHTS data in the health field, including the Surgeon General’s Call to Action to Promote Walking and Walkable Communities, Healthy People 2020,⁽¹¹⁾ part of The Department of Health and Human Services’ 10-year agenda, and the White House Task Force on Childhood Obesity.⁽⁵²⁾ These examples demonstrate how NHTS data are being used to benchmark progress on health goals and to encourage the development of policies and programs that will advance the nation’s health priorities. In its Report to the President, for example, the White House Task Force on Childhood Obesity(52)^(52)* makes specific policy recommendations for how to reach its goals, including enhancing Safe Routes to School Programs and reauthorizing a Surface Transportation Act that improves livability and encourages physical activity by adopting “Complete Streets” principles (e.g., new and improvement construction projects to accommodate bicyclists and walkers). NHTS data help lay the groundwork for these types of policy recommendations.

*Revised 4/18/2018

Table 9. Health field use of NHTS data.

Document	NHTS Data use	Purpose
Step It Up! The Surgeon General’s Call To Action To Promote Walking And Walkable Communities(12)	Identifies NHTS as one of the data sources for surveillance of active transportation.	Stimulate action nationwide to solve a major public health problem by promoting walking and walkable communities.
Morbidity and Mortality Weekly Report: Active Transportation Surveillance — United States, 1999–2012(53)	Referenced as a potential system to monitor certain types of physical activity (e.g., walking and bicycling).	Use five surveillance systems (one of which includes NHTS) to assess one or more components of active transportation. Help public health and transportation professionals monitor population participation in active transportation. Use data findings to plan and evaluate interventions that influence active transportation.
Vital Signs on Walking(54)	Length of walking trips, by different trip purposes.	Provide information on one of the CDC's “Winnable Battles,” an issue with a significant impact on health and known effective strategies to address it.
The White House Task Force on Childhood Obesity Report to the President, Solving the Problem of Childhood Obesity within a Generation(52)	Bike and walk trips to school (used as a baseline measure of “How Kids Get to School,” and set the goal of increasing by 50% (by 2015) the percentage of children who take walking and biking trips to school.)] school.)*	Serve as a call to action with specific recommendations for addressing obesity as well as benchmarks of success.
Healthy People 2020(11)	Biking and walking trips (used to provide a baseline measure and performance targets).	Outlines the Department of Health and Human Services’ 10 Human Services’ 10*-year agenda, providing national guidelines for public health. Used by health agencies in developing and prioritizing their programs.

*Revised 4/18/2018

In addition to the research related to physical activity, NHTS offers the opportunity to research other important public health issues. As the CDC official noted:

“Travel behavior and active transportation also intersect with public health through factors such as air quality, safety, access to care, etc., making NHTS valuable in examining those connections.”^[20]

3.2.3 State and Local Use of NHTS Data for Planning, Policy, and Project Decisionmaking

In addition to informing Federal policy and rulemaking, there are examples where NHTS data, particularly the Add-on sample, has been used to inform planning as well as policy and project development within State and local governments.

3.2.3.1 State and Local Transportation Policy and Planning

The NHTS data are used by numerous States and MPOs in developing, calibrating, or validating travel demand models that directly inform State or local policy and planning decisions. As one Add-on partner stated:

“Models are the only quantifiable source for transportation planning decisionmaking—NHTS is a must-have input to the models. All planning efforts are based on regional transportation models.”^[21]

Others use the State and local results (from the Add-on sample) directly to research State issues. Table 10 highlights a few examples of NHTS data use by States and MPOs for travel demand and travel planning purposes.

Table 10. State/MPO NHTS use for travel demand models and travel planning.^[22]

State	NHTS use	Purpose
New York	Add-on data reports (county level analysis). Validation of State travel demand models. Research on custom issues.	NY transportation department uses data to validate the travel demand model, which informs State projects and programs. Results used directly by MPOs for long-range planning. Research on origin-destination flow to assess employment related travel. Research on proximity to transit and related travel behavior.
Iowa	Data on trip rates and trip making characteristics are inputs to State and MPO travel demand models.	State and county level models used for transportation planning decisions.
Ohio, Kentucky, Indiana MPO (OKI)	Do not have MPO data. Use NHTS to “borrow” data from similar regions in neighboring States to create trip rates for MPO travel demand model.	The model is used by Ohio transportation department and MPO for long-range planning. MPO model also used as an input to the Ohio transportation department Certified Traffic Forecasts (provides input for projects).
Atlanta Regional Commission	Data from GA State Add-on sample used to benchmark MPO travel survey.	MPO travel survey used for regional planning decisions.
North Central Texas Council of Governments	Regional MPO researching use of TX State Add-on data to: Integrate into travel demand model. Look at trends from past MPO travel survey to present.	Support regional transportation planning.
Maricopa Association Governments(55)	NHTS Add-on sample used for travel demand model estimation and calibration.	Informed MAG’s Regional Transportation Plan.

 

3.2.3.2 Environmental and Energy Policy and Regulations

As previously described in Section 3.2.2, NHTS data are used by States and MPOs as one input to the MOVES model to estimate emissions. The results from these models enable States and MPOs to meet reporting requirements as specified in the Clean Air Act (CAA)(56)^(56)*. While Volpe does not know the extent to which NHTS data serves as an input to these air quality reports, several Add-on partners mentioned that NHTS serves this valuable function. In Vermont, Volpe found evidence of NHTS data being used to inform energy-related issues at the State level.

*Revised 4/18/2018

Table 11. State/MPO NHTS use for environmental and energy planning.^[23]

State	NHTS use	Purpose
Ohio, Kentucky, Indiana MPO	Regional travel demand model (see Table 11).	Future travel conditions from model feed into air quality reporting as required by State and Federal EPA. EPA MOVES software used for these forecasts.
Vermont	Daily travel demand and trip generation.	Estimate transportation energy use in the State and forecast electric vehicle travel demand and its likely adoption within the State. Data used as a basis for planning the placement of charging facilities throughout the State.

 

3.2.3.3 NHTS Use in the National Cooperative Highway Research Program (NCHRP)

Through its mission to address transportation issues integral to the State transportation departments, MPOs, and local governments, the NCHRP has developed guidebooks and reports to assist communities in multiple aspects of transportation planning. The NHTS is often a source of information used to develop the guidebooks as well as a source of data recommended to implement the transportation planning forecasts and techniques. These guidebooks are used to inform policy and projects at the regional, corridor, or project level.

Table 12. NCHRP reports using NHTS data.

Document	Examples of NHTS Data Use	Purpose
NCHRP 716 Travel Demand Forecasting: Parameters and Technique(57)	Use transferable parameters from the NHTS in the development of travel model components when local data are insufficient or unavailable. Check the reasonableness of model outputs (e.g., validation and calibration).	Provide guidance on travel demand forecasting procedures and their application for solving common transportation problems. Provide information on developing travel models.
NCHRP 770 Estimating Bicycling and Walking for Planning and Project Development: A Guidebook(58)	Includes transferable methods to estimate and forecast bicycling and walking. NHTS data includes walking, biking, transit trips; VMT/PMT; mode share; Distance traveled by bike; biker characteristics; and vehicle ownership.	Provide information on estimating and forecasting bicycling and walking activity. Multiple modeling approaches reviewed and compared.
NCHRP 758 Trip Generation Rates for Transportation Impact Analyses of Infill Developments(59)	Use of NHTS (or other travel survey data) to calculate trip generation rates used to compare to/adjust ITE published rates for Infill Development. NHTS data includes trip purpose/land use, mode, and trip characteristics.	Describe an easily applied methodology using travel survey data to prepare and review site-specific transportation impact analyses of infill development projects located within higher-density urban and suburban areas.

 

3.2.3.4 Project Selection and/or Modification

In trying to identify project level impacts of the NHTS data, Volpe primarily relied on its interviews with State and MPO contacts, as well as a literature review of State and local applications of the NHTS data. Based on these methods, Volpe found a range of examples in which NHTS data was used to inform transportation-related project selection or modification. In some cases, the data confirmed the need for a project (e.g., based on travel demand data) or enabled the State or MPO to prioritize projects. As one interview noted,

“We get lists of projects and funding is limited, so we use survey data to help us decide if investment in a project is worth it—the data may tip the balance of the scale one way or the other.”^[24]

Examples are summarized in Table 13.

Table 13. State/MPO NHTS data use for project selection or modification.^[25]

State	NHTS Use	Example Project
Ohio, Kentucky, Indiana MPO (OKI)	NHTS Add-on data used.	Ohio transportation department’s Brent Spence Bridge Project (Ohio River) used future traffic volumes calculated using the MPO travel demand model in the project design process.
Atlanta Regional Commission	State Add-on data used in conjunction with MPO survey data.	Used Add-on data to look at trip-making behavior in areas of concern; the data reinforces decisionmaking and helps prioritize project selection. Transit Project: NHTS data helped identify whether there was a need to re-route buses in the downtown area. Park and Ride: NHTS data supported decisions on where to invest in Park and Ride lots.
Iowa	Data on trip rate and trip-making characteristics used as inputs to travel demand models.	Using the model can assess impacts of proposed projects on trip rates in the area. Interchange project. Travel demand model used to assess several design scenarios for project. Model provided trip rates and congestion levels for scenario comparison (e.g., build vs. no-build). Corridor level projects: Similarly, for corridor level projects, such as capacity expansions, the travel demand model can assess impacts of the project on trip rates. Passenger Rail: Used NHTS to look at commute trip origin/destination patterns between Chicago, Iowa, and Omaha to assess potential for rail travel.
California(60)	Data on trip purpose, mode share, characteristics of households, and safety attitudes used; geographic analysis was also conducted.	Used NHTS California Add-on data on behavior and trends to identify barriers to pedestrian and bicycle travel; results enabled State to tackle these “low hanging” issues.
Florida(61)	National and Add-on sample used, including data on trip purpose, and personal, household, and travel characteristics.	Assessed transit markets in Florida, as well as U.S., from five perspectives: market size, modal share, attitudes, socio-demographics. and trip characteristics. Results can be used by transit agencies for strategic planning and more generally to develop policies and fund programs for those who are transportation and economically disadvantaged.

 

The interviews and literature search did not reveal any specific examples in which NHTS data informed a nontransportation-related project. Nonetheless, Volpe expects that there may be cases where NHTS did serve this role. For example, NHTS data forms the basis for several of the Physical Activity objectives presented in Healthy People 2020⁽¹¹⁾ (Section 3.2.2), and through the interviews, Volpe heard that the goals and objectives outlined in Healthy People 2020 provide agencies and organizations with funding opportunities and help guide the development of their projects and programs.

3.3   NHTS Responsiveness to its User Community

The success of the NHTS Program depends on its ability to meet the needs of its user community. The degree to which the NHTS interacts with and solicits feedback from the community reflects its responsiveness. This section focuses on documenting the different ways in which NHTS has collected information from its user community and how this feedback has led to changes in the program.

The evaluation questions used to assess how responsive the NHTS team is to its user community included the following:

• To what extent does NHTS use multiple methods to solicit feedback from its user community?
  
  
• Does NHTS continuously reach out to its user community?
  
  
• In what ways has NHTS made changes based on user feedback:
  
  
  • – To its outreach (e.g., tools, publications, etc.)?
    
    
  • – To its 2016 survey?

The NHTS receives extensive feedback from its user community through direct user support, outreach activities, and the NHTS task force. An Expert Panel has also been convened to provide input on the upcoming 2016 survey. These channels have provided the NHTS with direction in planning of the NHTS, the development of user tools, and in the creation of reports and presentations. The following section of the Report summarizes findings on the different mechanisms that NHTS uses to collect user input, the frequency with which it uses the methods, and changes that NHTS has made based on input from its user community.

3.3.1 Direct User Support

NHTS provides continuous support to its users through its website (www.nhts.ornl.gov), where it houses the datasets, user guidance documents, publications, and analysis tools. The NHTS also uses the website to keep its users updated on any news related to the survey.

FHWA receives ongoing feedback from users who contact FHWA Public Affairs or the NHTS staff directly for assistance. The NHTS team fields 2–4 data requests per week and fields user questions received by email or phone on an ongoing basis. Data analysts at Oak Ridge National Laboratory (ORNL) are also available to support users with more challenging data requests or data usage questions.

In each of the interviews, respondents were asked to comment on NHTS responsiveness to its user community. Overall, the response was extremely positive. As one interviewee stated:

“Overall, they do a great job of supporting users and provide service to all without fee.”^[26]

Another user indicated the following:

“Any time I have questions, Adella and her team are there to answer the questions.”^[27]

Lead users and task force members all describe a very collaborative relationship with the NHTS staff. As one lead user explained:

“NHTS appreciated and incorporated the [task force] feedback. One change made as a result of feedback obtained by [the] task force—NHTS created a differential for weekday data to meet needs of Add-ons.”^[28]

In another example of the collaboration that exists between NHTS and its user community, a lead user commented that when his team found anomalies in the 2009 data, NHTS pulled, investigated, and reweighted the data based on the user’s feedback.

Several interviewees noted that resource constraints limit the amount of outreach that can be performed.

“NHTS is very constrained in resources—things like webinars [and] training modules can be done with [a] relatively modest budget, but [it is] hard to do a lot more outreach.”^[29]

“Given constraints NHTS Program office operates under, they do a good job updating the user community.”^[30]

In addition, another user would like to see a more formal means of communicating survey needs.

“What’s missing is a mechanism for users to make their needs known – need a situation where people feel they can describe their data needs and NHTS will a) understand, and b) act on it.”`^[31]

The NHTS Program Manager also acknowledged that there are many demands on the NHTS survey, but the survey has “limited real estate.” In making decisions on what new content to add, the Program Manager uses input from the user community, but is also guided by the priorities of the Office of the Secretary, TRB programming, topics in the media, as well as other sources. According to the Program Manager, she is, “always listening and tuning into key policy issues of the day.”

3.3.2 Outreach Activities

On an informal level, the NHTS Program Manager reaches out to agencies across the government to understand the ways in which the NHTS data might serve their needs. For example, there has been a brown bag lunch with HUD and meetings with the EIA and CDC. As another mechanism of sharing insights and gathering input, the NHTS holds formal conferences and workshops for its users shortly after the NHTS data have been released. Two key examples include the following:

• Using National Household Travel Survey Data for Transportation Decisionmaking—Workshop (June 2011).
  
  
• Data for Understanding Our Nation's Travel: National Household Travel Survey Conference (November 2004).

For the two-day workshop convened in 2011, more than 60 presentations using NHTS were given, along with 22 posters. This workshop offered users the opportunity to share insights, issues, or challenges in using the NHTS data.

Other key outreach activities include presentations and panel sessions at the annual meeting of TRB, as well as updates to key TRB committees (e.g., Travel Survey Methods Committee). These outreach activities provide the opportunity for the NHTS user community to share how they use of the NHTS data, while also providing feedback on the survey methodology, dataset, and analysis tools. Table 14 lists major NHTS outreach activities in the last 11 years.

Table 14. 15-year review of formal NHTS outreach activities.

Outreach Type	Title	Date
Annual TRB Meeting	Session 302: Innovative Analysis of National Household Transportation Survey Session 602: Panel, Continuous, and Cross-Sectional Travel Surveys: Lessons Learned and Successes Achieved Session 799: Data Needs for the Future—The Big Picture	January 2015
Annual TRB Meeting	Session 197: Planning for 2015 National Household Travel Survey Session 244: Travel Characteristics Past, Present, and Future: Communicating Information Derived from National Household Travel Survey, Part 1 Session 384: Travel Characteristics Past, Present, and Future: Communicating Information Derived from National Household Travel Survey, Part 2 Communicating Information Derived from National Household Travel Survey, Part 2*	January 2014
Annual TRB Meeting	Session 190: The Future of National Household Travel Data: Getting Feedback from the User Community	January 2013
Annual TRB Meeting	Session 339: Turning Past Experience into Future Plans for the National Household Travel Survey	January 2012
Workshop	Using National Household Travel Survey Data for Transportation Decision Making	June 2011
Annual TRB Meeting	Session 181: National Household Travel Survey: data Tools and Overview of Trends	January 2011
Annual TRB Meeting	Session 710: National Household Travel Survey: Data Applications, Tools, and Analyses Session 720: Emerging Issues and National Household Travel Survey Data Applications	January 2010
Annual TRB Meeting	Session 790: National Household Travel Survey, 2008: Add-on Applications, Data Use, and Dissemination	January 2009
Annual TRB Meeting	Session 119: Application of Passenger Travel Data for National, State, and Local Congestion Performance Measurement	January 2008
Annual TRB Meeting	Session 380: Showcase of Nationwide Personal Transportation Survey and National Household Travel Survey Data Analyses and Applications	January 2007
Annual TRB Meeting	Session 394: National Data Requirements and Programs: What Do We Have? What Do We Need?	January 2006
Annual TRB Meeting	Session 383: Data Needs and Sources for Nonautomobile Modes: Emerging Technologies for Nonmotorized and Two-Wheeled Vehicles	January 2005
Annual TRB Meeting	Session 732: Travel Behavior Trends from 2001 National Household Travel Survey	January 2004
Conference	Data for Understanding Our Nation's Travel: National Household Travel Survey Conference (Transportation Research Circular Number E-C071)	November 2004

*Revised 4/18/2018

Recently, the NHTS team has added regional workshops with current and potential Add-on partners to their outreach activities. These workshops allow MPOs, State transportation departments and other groups to share their needs and concerns with the Add-on portions of the NHTS. For example, NHTS staff traveled to Colorado and Arkansas to hear about their concerns and understand their needs with regard to the survey.

In addition, FHWA has contracted the services of a consulting firm, Battelle Memorial Institute, to help States and MPOs assess their data needs and whether or not the NHTS is an appropriate vehicle to answer their questions (regardless of whether or not the State or MPO is an Add-on partner). The contractor provides methodology support, helping States and MPOs determine necessary sample sizes based on the analysis they plan to conduct. For example, Battelle held several conference call meetings with the Arizona Add-on partner to discuss their objectives in joining the NHTS and sample size appropriateness to capture those objectives. Battelle then ran computation exercises using the 2009 data and provided Arizona with a couple of different scenarios for how it might allocate its sample across counties to meet its objectives.

3.3.3 NHTS Task Force

More recently, a central part of NHTS outreach has been the NHTS task force. In 2011, the NHTS Program developed the task force to bring the user perspective to the NHTS as it prepared for its next survey. The task force serves as a bridge between FHWA (NHTS team) and the NHTS user community by soliciting input from users and facilitating discussions with them. The NHTS Program Manager meets monthly with members of the NHTS task force to obtain updates on their activities.

The objective of the NHTS task force was to understand how the NHTS community uses NHTS data and how potential survey modifications would impact the community. Through sessions and workshops at TRB, user forums at other transportation research events, a user survey, and phone calls with the user community, the 22-member Task Force gained an understanding of the needs and experiences of this community.

In October 2013, the NHTS task force presented its phase 1 findings in the Transportation Research Circular E-C178. Although no formal recommendations were made by the task force, its findings provided detailed user feedback on the previous NHTS and data needs for future NHTS. The circular provided data on themes including the following:

• How NHTS data are used.
  
  
• How well NHTS data meet user needs.
  
  
• Additional data desired for next NHTS/additional data needs.
  
  
• Sampling and under-represented population groups.
  
  
• Survey frequency.

3.3.3.1 Summary of Task Force Findings

The NHTS task force found that NHTS is widely used for a variety of purposes by many different user groups. Needs of users differ widely, but there is extensive need for national trend analysis. NHTS fulfills its mission as a nationally representative survey of travel behavior, but it falls short of what many users would like, including the following:

• Many users would like the NHTS to be conducted more frequently.
  
  
• Users have concerns that the RDD sample no longer accurately represents U.S. households (oversamples elderly, under samples young, omits cellphone-only households).
  
  
• NHTS data are used for a wide variety of purposes by many different user groups; some groups’ needs are met while others feel that the data falls short of delivering what they need.
  
  
  • – Likes include that data are easy to use and available in multiple formats.
    
    
  • – Dislikes, especially among modelers, were inclusion of weekend and holiday data in sample (leading to smaller effective sample), and missing data from some household members.
    
    
• Users are increasingly interested in statistically valid data of more detailed geographies, including MPOs and rural areas.
  
  
• Users would like the next NHTS to take advantage of technical advances in survey sampling, design, and data collection (e.g., GPS data), but also want comparability with previous surveys.
  
  
• Users need more help translating data into useful information. Additional and more flexible tools are desired and information on how to fuse with other datasets.

The findings also note that the NHTS may not be reaching all its potential users and that its value could be increased with better guidance on how to fuse it with other standard data sets.

3.3.4 Changes to the NHTS

The NHTS Program has enhanced its website and its online tools based directly on feedback from its user community. Questions and data requests from the user community are often the basis for the NHTS website’s FAQs. For example, in 2011, NHTS issued FAQs detailing Urban-Rural Designations and Trip Purpose (variables in the dataset), because of questions on these topics from the user community. User feedback led to the development of online analysis tools such as the Table Designer and Data Extraction Tools. These tools allow users to access multiple years of data at any time. User requests and feedback also inform the topics selected for briefs, reports, and the pre-loaded tables that are included on the website.

In addition, the development of the NHTS Academy is based on feedback from the user community. During a task force event in Dallas Texas, the Chief of Travel Monitoring and Surveys Division learned that NHTS users wanted “self-paced learning tools.” In response to this request, the NHTS team developed the NHTS Academy—a series of short informational videos designed to help the user community understand and make better use of the NHTS data. The NHTS designs modules that are based on recurring issues or problems among its users.

Based on the task force findings and input from the broader user community, the NHTS has also made significant changes to the methodology for its upcoming 2016 survey.^[32] There was concern that the 2009 NHTS was over-representing the elderly and did not include younger, cell-phone only households, so the methodology has been updated to better represent U.S. households, with the objectives of maximizing response and minimizing bias. Key changes to the survey include the following:

• Move from RDD sample to an Address-Based Sample.
  
  
• Conduct recruiting using a mail out/mail back method (rather than CATI).
  
  
• Provide mail, phone, and email reminders to recruits to encourage response.

In response to complaints of missing data from family members, make the following changes:

• Change retrieval of travel diary data to web retrieval survey (instead of CATI), with option to complete by phone (with interviewer using web survey).
  
  
• Provide diaries for each household member.

In response to the greater use of activity-based modelling in the user community, the NHTS survey is being redesigned to collect activities at each stop. Based on Add-on members’ complaints about having to pay for unwanted weekend and holiday data, Add-on participants will have the option to collect only one day of sample over weekend travel instead of two days of weekend sample.

3.3.5 Expert Review Panel⁽⁶²⁾

In developing its survey methodology for the 2016 survey, NHTS convened a panel of survey research experts to obtain their input and review. The first panel meeting was held in March 2014. NHTS summarized the findings from the panel in detailed notes. The panel met again in April 2015 to provide input on all aspects of the methodology. NHTS is using the feedback from the expert panel to inform its decisions about the administration of the 2016 survey.

3.4   Challenges and Lessons Learned

Challenges and lessons learned were documented in reference to the overall NHTS Program as well as the Add-on program. Findings for each are presented in this section.

3.4.1 NHTS Program

Challenges and lessons learned regarding the NHTS Program are based on data gathered during the interviews. Specific questions were included in the discussion guides for the current and previous program managers, as well as for the Chief of the Travel Monitoring and Surveys Division. Lead users, while not prompted, still mentioned challenges, as well as suggestions for how to address those challenges. Their responses are included in the findings.

Interviewees were asked to comment on challenges and lessons learned in three areas:

• Survey planning process.
  
  
• Survey administration and oversight.
  
  
• Outreach.

3.4.1.1 Survey Planning Process

Interviewees identified several challenges and lessons learned regarding the NHTS planning process. Many saw funding as one of the biggest issues for survey planning. Specifically, the lack of institutionalized funding results in the NHTS being perceived as not a high priority. One lead user noted that “without consistent, stable funding the program cannot run in a systematic fashion.” Other interviewees expressed concern that the lack of stable funding negatively affected States’ use of the survey. For instance, one said that:

“Financial planning is critical. States will not come on board without funding.”^[33]

Several interviewees suggested that there is a lack of resources (e.g., staffing) that additional funding could help support. On a similar note, one lead user expressed disappointment in having to defend something that “should be so obvious.”

Several interviewees suggested that if the NHTS was conducted on a regular cycle with dedicated funding, it could be more effective. They noted that the irregularity of the survey and long lapses of time between surveys results in States perceiving the NHTS as unreliable. One interviewee said:

“NHTS has historical continuity; however, it will be 7.5 years since the last survey. [FHWA] will lose people if [they] can’t provide data on a more regular basis.” The unpredictable timing of the survey hinders Add-on partners’ ability to count on when they will have their data, which affects a [State’s] ability to participate as an Add-on altogether.^[34]

Others raised the concern that because technology is changing our travel behavior so rapidly, it is important to conduct the survey at more regular intervals in order to capture these changes in travel.

Another issue raised is related to the survey method design and content. An interviewee suggested that it will be challenging to determine how effective a web-based survey will be given the length and complexity of the NHTS. Furthermore, it is unclear how the changes in methods will impact the data, and hence the trends in travel behavior. (e.g., To what extent will NHTS be able to distinguish changes because of survey method from changes because of travel trends?) Another interviewee suggested that in the future:

“[There are] new and different ways of collecting data, e.g., credit cards and cell phones… NHTS needs to be on its game…needs to know when to change its methods and when to defend what they are doing.”^[35]

3.4.1.2 Survey Administration and Oversight

Interviewees discussed challenges and lessons learned regarding the NHTS administration and oversight process. One of interviewees commented on both monitoring progress and data cleaning, noting that:

“A great step forward was taken by Adella Santos in the 2009 NHTS, by requiring the creation of daily online updates on the status of the sample during the recruit and retrieval survey stages.”^[36]

The interviewee indicated that there are plans with the 2016 survey to provide more information throughout the year-long survey field period to address “the quality, completeness, and coherence of the data,” and that effort should be made to test the effectiveness of this monitoring. The same interviewee also noted that performing the data cleaning in a shorter amount of time is a challenge. Ideally, there would be less lag time between the end of data collection and publication of the public-use dataset.

Interviewees offered several recommendations for improving the administration and oversight of NHTS. Several of the key recommendations include the following:

• Develop NHTS into a family of surveys that would have some specialized data collection for issues such as long-distance travel, use of emerging modes (e.g., Uber and Lyft), and connections between travel behavior and health status.
  
  
• Consider linking NHTS data to supplemental data, such as cellphone locations.
  
  
• Strengthen relationships in the administration for sharing the uses of the data.
  
  
• Adopt a more systematic approach to post survey analysis. A lot of the data seemingly goes unanalyzed because people just use what they are interested in studying, rather than the entire dataset.

3.4.1.3 Outreach

Several challenges and lessons learned regarding effective NHTS outreach methods were raised in the interviews. A few interviewees commented on challenges in doing outreach and getting user input. Several users indicated that more outreach is needed to bring in the opinions of others, including those from nontransportation Federal communities.

Another user suggested that the task force should be more proactive in getting user input on the 2020 survey and added that that type of outreach should occur several years in advance of the survey. One user suggested that effective user outreach could help address the challenge of balancing new issues with core questions (i.e. trend data are very important, but travel behavior changes and new issues arise; NHTS needs to get rid of obsolete data and cover new phenomena). Several interviewees also identified resource constraints (e.g., staffing) as a cause for this lack of outreach. One interviewee noted that they:

“[NHTS] needs to have dedicated staff for outreach. [They] also need staff that is trained to analyze data.”^[37]

Another area of concern was the lack of outreach to and access of data for decisionmakers (i.e. policy makers). One user noted that:

“Congressional staff has an idea of what their data needs are but they can’t articulate them.”^[38]

Another emphasized the need to improve decisionmakers’ access to NHTS data:

“Legislative staff wants the ability to go online and get information—recent information, quick and simple. They are not going to hunt around for what they are looking for; if it’s not there, they are going to move on.”^[39]

Furthermore, one user indicated that the NHTS staff does not always understand the policy audience.

Other interviewees identified some specific recommendations for improving outreach of NHTS, including the following:

• Need to brand NHTS data better so decisionmakers can really gauge its impact in addressing issues. It is often not cited properly, which makes it lose credit. This makes supporting future surveys in the NHTS more of a challenge.
  
  
• Need more training on the uses of NHTS data and for the Add-on programs. NHTS could provide webinars for the user community on various reasons why decisions were made (e.g., categorization of income levels, weighting and controlling measures, effects of change in survey methods, etc.). NHTS also could conduct more usage training sessions for internal State transportation offices. They need to conduct more external outreach efforts to more States, MPOs, and private entities for next NHTS.

3.4.2 Add-on Program

During the interviews, Add-on partners were asked to identify any challenges of the NHTS Add-on program. A summary of their responses is presented below. It should be noted that the views expressed only represent feedback from a relatively small number of States and MPOs and are not meant to be representative of the views of all Add-on partners.

When asked about challenges, a couple of Add-on partners mentioned a lack of communication between the States. Interviewees expressed a desire to see increased communication among the Add-ons to get a better sense of what other States are doing (e.g., what questions they are asking and can States and MPOs support each other as they collect data). For instance, one interviewee noted that a big “weakness is not having other States’ data. In New York, a lot of the traffic goes out of State, but none of those States participate in the Add-on.”

One suggestion was to consider creating a community of Add-ons (e.g., face-to-face meeting, listserv) to put them in touch with each other. Furthermore, there was some miscommunication between the regions and NHTS team in terms of what type of data the regions need. For example, in one case the regions were using Monday through Friday travel models, but the NHTS collected data based on seven day weeks. A significant amount of money ended up being spent covering days of the week that the State did not want. As mentioned above, lack of funding was identified as a barrier for getting more States on board.

Interviewees reinforced the importance of the survey being flexible. One interviewee referenced an example of how they could not get questions on tolling into the survey for Florida. Another interviewee indicated that States necessarily lose some flexibility and control when they become Add-on partners because they are not managing the survey nor can they make changes to the methods. However, he went on to say that NHTS is a “solid survey” that provides a good option for many States and MPOs, particularly smaller ones that may not have the resources or expertise to collect their own data. Another issue that was raised is that technology is rapidly changing, and the NHTS needs to adapt to those rapid changes in order to be successful. Interviewees recognized that the NHTS faces several constraints such as its limited funding and the need to negotiate with its consultants.

Other challenges included the need for more training and tools and improved quality of the survey. Two interviewees suggested that there need to be more tools to help States and MPOs more easily analyze the data, including tools for data visualization. This is particularly important for smaller States and MPOs that may not have staff with survey or statistical expertise. Another interviewee stated that the 2009 survey did not meet the expectations of Add-on partners. They suggested that the NHTS team needs to:

“...understand the objectives of Add-ons, set correct expectations for what Add-ons can do, provide updates during planning, and provide information and feedback during data collection and completion.”^[40]

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⁷ For the trend analysis, when the NHTS original categorization is used, 56 percent of publications in the 2014 Compendium are classified as transportation topics (Figure 10). Using the Volpe categorization, however, that statistic is 46 percent (Figure 7), because Volpe added a separate topic for health.

⁸ Values in parentheses equal the number of Compendium publications for that particular year.

⁹ Non-transportation topics/fields include energy, environment, and survey methods and data analysis.

¹⁰ FHWA Staff, in-person interview conducted by Margaret Petrella (Volpe) and Lora Chajka-Cadin (Volpe). March 2015.

¹¹ Former FHWA Staff, in-person interview conducted by Margaret Petrella (Volpe) and Lora Chajka-Cadin (Volpe). March 2015.

¹² Transportation Consultant, phone interview conducted by Margaret Petrella (Volpe), April 2015.

¹³ Transportation Consultant, phone interview conducted by Margaret Petrella (Volpe) and Lora Chajka-Cadin (Volpe). April 2015.

¹⁴ Transportation Consultant, phone interview conducted by Margaret Petrella (Volpe) and Lora Chajka-Cadin (Volpe). April 2015.

¹⁵ The 2007 Energy Independence and Security Act (EISA), requires that the US DOT establish CAFE standards separately for passenger cars and light trucks each model year.

¹⁶ Transportation Consultant, phone interview conducted by Margaret Petrella (Volpe) and Lora Chajka-Cadin (Volpe). April 2015.

¹⁷ Advancing Automation is a central priority in the 2015-2019 Intelligent Transportation Systems (ITS) Strategic Plan developed by the ITS Joint Program, and self-driving vehicles are also featured in the Secretary's Beyond Traffic: 30 Year Outlook report.

¹⁸ FHWA Staff, in-person interview conducted by Margaret Petrella (Volpe) and Lora Chajka-Cadin (Volpe). March 2015.

¹⁹ CDC Researcher, email follow-up to phone interview conducted by Margaret Petrella (Volpe). April 2015.

²⁰ CDC Researcher, email follow-up to phone interview conducted by Margaret Petrella (Volpe). April 2015.

²¹ NHTS Add-on Partner, phone interview conducted by Margaret Petrella (Volpe). April 2015.

²² Information obtained through interviews with the evaluation team.

²³ Information obtained through interviews with the evaluation team.

²⁴ NHTS Add-on Partner, phone interview conducted by Margaret Petrella (Volpe). April 2015.

²⁵ Information obtained through interviews with evaluation team.

²⁶ Transportation Consultant, phone interview conducted by Lora Chajka-Cadin (Volpe). March 2015.

²⁷ NHTS Add-on Partner, phone interview conducted by Lora Chajka-Cadin (Volpe). May 2015.

²⁸ Transportation Consultant, phone interview conducted by Lora Chajka-Cadin (Volpe). May 2015.

²⁹ Academic, phone interview conducted by Margaret Petrella (Volpe). April 2015.

³⁰ Transportation Consultant, phone interview conducted by Lora Chajka-Cadin (Volpe). May 2015.

³¹ Transportation Consultant, phone interview conducted by Margaret Petrella (Volpe) and Lora Chajka-Cadin (Volpe). April 2015.

³² The changes to the 2016 survey presented in this section are the NHTS proposed changes, which are currently under review at the Office of Management and Budget. A summary of final changes may not be ready until November or December 2015.

³³ FHWA Staff, phone interview conducted by Margaret Petrella (Volpe) and Lora Chajka-Cadin (Volpe). May 2015.

³⁴ Ibid.

³⁵ Academic, phone interview conducted by Margaret Petrella. April, 2015 April 2015*.

³⁶ FHWA Staff, email correspondence, September 2015.

³⁷ Transportation Consultant, phone interview conducted by Margaret Petrella (Volpe), April 2015.

³⁸ Transportation Consultant, phone interview conducted by Margaret Petrella (Volpe) and Lora Chajka-Cadin (Volpe). April 2015.

³⁹ Senior Associate Consultant, phone interview conducted by Lora Chajka-Cadin (Volpe), May 2015.

⁴⁰ Research Scientist, phone interview by Lora Chajka-Cadin (Volpe). March 2013.

*Revised 4/18/2018