Data on Health and Well-being of American Indians, Alaska Natives, and Other Native Americans. National Household Travel Survey (NHTS)

12/01/2006

Sponsor: U.S. Department of Transportation/Federal Highway Administration, Bureau of Transportation Statistics, and National Highway Traffic Safety Administration
Description: The 2001 National Household Travel Survey (NHTS) was developed to gather comprehensive data on travel and transportation patterns in the United States. Data were collected on daily trips taken in a 24-hour period, as well as long distance trips collected for the 4-week period prior to the travel day. Data collected for the daily trips include the purpose of the trip, the means of transportation used, how long the trip took, when the trip took place, and characteristics of private vehicle ownership. The survey measured personal travel, which excluded travel made as part of the respondents job (i.e., business trips). The NHTS data are used primarily for gaining a better understanding of travel behavior. For example, NHTS data are used to quantify travel behavior, analyze changes in travel characteristics over time, relate travel behavior to the demographics of the traveler, and study the relationship of demographics and travel over time. Additionally, people in fields outside of transportation use the NHTS data. For example, social service agencies may use the data to learn more about how low-income households currently meet their travel needs.

In addition to the national sample, planning organizations could purchase add-on surveys in their state or specific county so that reliable estimates could be made for that geographic area. The nine add-on samples include the following areas:

  • State of Wisconsin
  • State of New York
  • State of Texas
  • Hawaii (state-wide, excluding Oahu)
  • Oahu, Hawaii
  • Baltimore, Maryland
  • Des Moines, Iowa
  • Lancaster, Pennsylvania
  • Edmonson, Carter, Pulaski, and Scott Counties, Kentucky
Relevant Policy Issues: Transportation Availability.
Data Type(s): Survey
Unit of Analysis: The NHTS data are organized into five different data files and contain data on the 26,038 households from the national sample, and the 43,779 completed add-on households. There were over 160,000 person interviews from the national sample and add-on households, with about 100,000 of them from the add-on sample. Records from each data file can be linked to one another using the Household ID number. Descriptions for each data file are as follows:
  • Household file: Contains one record per sampled household. Variables include the number of vehicles, type of residence, household income, and information on the primary household respondent.
  • Person file: Contains one record per person who completed a person interview. Variables include information on traveling to work; the number of miles driven; customer satisfaction with transportation arrangements; and person demographics such as age, race, driver status, and medical condition.
  • Vehicle File: Contains one record per each vehicle owned, leased, or available for regular use by the household members in each sample household. Variables include type of vehicle, vehicle ownership, mileage, and housing characteristics.
  • Travel day trip file: Contains one record per each trip taken by an interviewed person in a sampled household, for the households randomly- assigned travel day.
  • Long trip file: Contains one record per each trip of 50 miles or more away from home. The long distance trip data were collected in the national sample and NY and WI add-on samples only.

For the NHTS study, household members include all people who think of the sampled household as their primary place of residence. It includes persons who usually stay in the household but are temporarily away on business, vacation, or in a hospital. It does not include people just visiting, such as college students who normally live away at school.

Identification of AI/AN/NA: Race is self-reported, using the following survey item:

Im going to read a list of races. Please tell me which best describes your race. Are you ...
(Interviewers are instructed to code all that apply.)

  • White
  • African American, Black
  • Asian
  • American Indian, Alaskan Native (AI/AN)
  • Native Hawaiian, or other Pacific Islander (NH/PI)

The following categories are not asked but are coded in the data files:

  • Multiracial
  • Hispanic/Mexican
  • Other
  • Refused
  • Dont Know
AI/AN/NA Population in Data Set: 2001 NHTS Household File
Total number of records: 69,817 households
AI/AN primary household respondent: 401
NH/PI primary household respondent: 370
White/AI primary household respondent: 547
AI/Hispanic primary household respondent: 44

2001 NHTS Person File
Total number of records: 160,758 completed interviews
AI/AN person in household: 882
NH/PI person in household: 1,027
White/AI person in household: 1,275
AI/Hispanic person in household: 115

2001 NHTS Vehicle File
Total number of vehicles: 139,382
AI/AN primary driver: 697
NH/PI primary driver: 720
White/AI primary driver: 1,189
AI/Hispanic primary driver: 62

2001 NHTS Day Trip File
Total number of day trips: 642,292
AI/AN traveler: 3,383
NH/PI traveler: 3,794
White/AI traveler: 4,834
AI/Hispanic traveler: 413

2001 NHTS Long Trip File
Total number of long trips: 45,165
AI/AN traveler: 277
NH/PI traveler: 127
White/AI traveler: 609
AI/Hispanid traveler: 24

Geographic Scope: The geographic scope of the study is national. Geographic indicators included are state, Census division, Census region, and Metropolitan Statistical Area (MSA) or Consolidated Metropolitan Statistical Area (CMSA).

The NHTS data are supplemented with tract and block group data that are derived from the 2000 Census data. These data are used to describe the characteristics of the areas where the NHTS respondents live, including descriptors such as housing units per square mile, an urban/rural code, and population density per square mile.

Date or Frequency: The NHTS interviews were conducted from April 2001 through May 2002. The NHTS resulted from integrating two national travel surveys: the Federal Highway Administration-sponsored Nationwide Personal Transportation Survey (NPTS) and the Bureau of Transportation Statistics-sponsored American Travel Survey (ATS). The NPTS collected detailed information on personal travel patterns using daily travel surveys, and was conducted in 1969, 1977, 1983, 1990, and 1995. The ATS obtained information about long-distance travel of persons living in the United States and was collected in 1977 and 1995.
Data Collection Methodology: Data collection consisted of three main phases. First, a household interview was conducted using computer assisted telephone interviewing (CATI) technology. The household interview was designed to collect information about the household, household members, and vehicles available to the household, and to elicit participation in the travel diary task. Next, travel diaries were mailed to the households. Each household in the sample was assigned a specific 24-hour Travel Day and kept diaries to record all travel by all household members for the assigned day. Respondents were also asked to document a 28-day Travel Period in order to collect longer-distance travel (over 50 miles from home) for each household member, including information on long commutes, airport access, and overnight stays. The assigned travel day was the last day of the assigned travel period. For a household to be included in any of the data sets, interviews had to be completed with at least half of the household adults. Finally, for the national sample and the New York and Wisconsin add-on samples, odometer readings from the household vehicles were collected from the respondent.
Participation: Optional, with incentives.
Response Rate: Overall weighted response rates were 41.2 percent for the national sample and 38.9 percent for the full sample (includes national sample and 9 add-on samples). These response rates were an improvement from the previous 1995 survey response rates, and are considered high for travel surveys of this type.
Sampling Methodology: NHTS collected travel data from the civilian, non-institutionalized population of the United States. Sampling was done by creating a random-digit dialing (RDD) list of telephone numbers. The sampling frame consisted of all telephone numbers in 100-banks of numbers in which there was at least one listed residential number. (Each 100-bank contains the 100 telephone numbers with the same area code, exchange, and first two of the last four digits of the telephone number.)
Analysis: The NHTS is a weighted data set. The weights reflect the selection probabilities and adjustments to account for nonresponse, undercoverage, and multiple telephones in a household. To obtain estimates that are minimally biased, weights must be used. Tabulations without weights may be significantly different than weighted estimates and may be subject to large bias. There are separate sets of weights for the full sample and for the national sample. For each set, there are household weights, person weights, travel day and travel period weights. The NHTS methodology report describes the process for applying the weights appropriately.
Strengths: There are multiple years of data available. Documentation for the NHTS is readily available, very detailed, and extremely clear.
Limitations: During the 2001 NHTS data collection period, the September 11th terrorist attacks occurred and severely disrupted travel in the United States for months. These attacks altered the amount and modes of travel that were being documented during this data collection.

Although there are multiple years of data available for comparison purposes, aggregation of the data is not recommended. The sample design varied across administrations of the survey. Also, there were changes in national travel behavior across the years of data collection due to the state of the economy, the price of oil, and the terrorist attacks of September 11, 2001. Some significant variations can be expected in travel trend analysis, but the nature of these variations is such that aggregation of the data across multiple years is discouraged.

As the data from the NHTS study is organized into four separate files, it may require strong programming skills to merge the files together if this is required for a specific research questions.

Access Requirements and Use Restrictions: The public use data are available to the public at no cost.
Contact Information: Federal Highway Administration/DOT
The Office of Highway Policy Information (HPPI)
Rm 3306
Washington, DC 20590
Phone: (202) 366-5021
Fax: (202) 366-7742

The NHTS public use database can be downloaded directly from: http://nhts.ornl.gov/2001/html_files/download_directory.shtml.

 

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