Survey Information
The Vehicle Inventory and Use Survey (VIUS) provides data on the physical and operational characteristics of the Nation's truck population. This survey is conducted every 5 years as part of the economic census. Title 13 of the United States Code (Sections 131, 191, and 224) directs the Census Bureau to take the economic census every 5 years, covering years ending in 2 and 7.
The 1997 VIUS is a probability sample of private and commercial trucks registered (or licensed) in the United States as of July 1, 1997. This survey excludes vehicles owned by Federal, state, or local governments; ambulances; buses; motor homes; farm tractors; unpowered trailer units; and trucks reported to have been sold, junked, or wrecked prior to July 1, 1996. A sample of about 131,000 trucks was surveyed to measure the characteristics of nearly 75 million trucks registered in the United States.
Additional Overview Information.
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The economic census is the major source of facts about the structure and functioning of the Nation's economy. It provides the framework for such composite measures as the gross domestic product, input/output measures, production and price indexes, and other statistical series that measure short-term changes in economic conditions.
VIUS data are of considerable value to government, business, industry, academia, and the general public. Data on the number and types of vehicles and how they are used are important in studying the future growth of transportation and are needed in calculating fees and cost allocations among highway users. The data also are important in evaluating safety risks to highway travelers and in assessing the energy efficiency and environmental impact of the Nation's truck fleet. Businesses and others make use of these data in conducting market studies and evaluating market strategies; assessing the utility and cost of certain types of equipment; calculating the longevity of products; determining fuel demands; and linking to, and better utilizing, other data sets representing limited segments of the truck population.
The 1997 VIUS is a probability sample of about 131,000 trucks registered in the United States as of July 1, 1997. This survey consists of an initial and a supplementary sample of truck registrations. A description of each sample follows.
Initial sample. The sampling frame for the initial universe was constructed from files of active truck registrations for the 50 states and the District of Columbia. All registrations on the sampling frame were identified as being active as of July 1, 1997.
The frame was stratified by geography and truck characteristics. The 50 states and the District of Columbia made up the 51 geographic "state" strata for the initial sample. Body type and gross vehicle weight (GVW) determined the following five truck strata: (1) pickups; (2) vans, minivans, and panels; (3) light single-unit trucks (GVW < 26,000 lb); (4) heavy single-unit trucks (GVW >= 26,000 lb); and (5) truck-tractors. Therefore, the sampling frame for the initial sample was partitioned into 255 geographic-by-truck strata. Within each of these strata, a simple random sample of truck registrations was selected, resulting in an initial sample of approximately 128,000 truck registrations.
Supplementary sample. Each truck represented on the sampling frame for the initial universe had associated with it a state of registration and a state as part of its mailing address. In the 1997 VIUS initial sampling frame and in previous TIUS sampling frames, a truck registered in a state other than the one listed on its mailing address was excluded. (For example, a truck registered in Florida that had a mailing address in Wisconsin was excluded from the sampling frame.) Therefore, previous TIUS estimates did not include data from these trucks. In order to represent these trucks in the 1997 VIUS estimates, a supplementary sample was selected independently from the initial sample.
Additional Sample Design Information.
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For each selected truck, a questionnaire was mailed to the registered owner. The registered owner was requested to provide data about the truck identified by the vehicle registration information imprinted on the questionnaire, regardless of whether or not the truck was still in his or her possession. The information provided by each respondent was subjected to extensive computer edits. Questionable responses were reviewed and corrected when necessary.
The VIUS utilized two questionnaires. The TC-9501 form was mailed
to the registered owners
of trucks in stratum 1
and 2. The TC-9502 form was mailed to the owners of trucks in
stratum 3, 4, and 5.
The questionnaires
can be accessed by clicking on the links provided.
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An estimate based on a sample survey potentially contains two types of errors: sampling and nonsampling. Sampling error occurs because characteristics differ among sampling units and because only a subset of the entire population is measured in a sample survey. Nonsampling error encompasses all other factors that contribute to the total error of a sample survey estimate. The accuracy of a survey result may be affected by these two types of errors.
Sampling and nonsampling errors are often measured by the quantities, bias and variance. The bias of an estimator of an unknown population value is the difference, averaged over all possible samples of the same size and design, between the estimator and the unknown population value. Any systematic error or inaccuracy that affects the reported data from all sampling units in a similar way will cause the resulting estimates to be biased. Variance is the squared difference, averaged over all possible samples of the same size and design, between an estimator and its average value.
Additional Reliability of Estimates
Information.
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Surveys: The results of the 1997 VIUS are comparable to the 1992 and prior Truck
Inventory and Use Surveys (TIUS). We changed the survey name to account for areas of future expansion,
including the possible addition of automobiles and buses. The following specific changes were made:
State data releases for the 1997 VIUS
became available in early October 1998. These data releases were issued on a flow
basis over the next year as they were completed. The U.S. Summary was released in October 1999.
All data releases were issued on the Internet at:
http://www.census.gov/svsd/www/97vehinv.html as PDF (portable document format)
files and are on this CD-ROM as well. The U.S. Summary is also available in print.
The U.S. Summary and state data releases include
summarized data that cover the characteristics of the Nation's private and
commercial fleets, such as the number of vehicles, number of truck miles,
major use, annual miles, model year, body type classification of operator,
and annual mileage by commodity line categories.
For more information on any 1997 VIUS product, see our web site (http://www.census.gov/econ/www/viusmain.html) or call Customer Services at 301-457-4100.
Users of transportation data may also be interested in the following Census programs:
Commodity Flow Survey provides data on shipments by domestic establishments classified
in mining, manufacturing, wholesale, and selected retail industries. Published aggregate
data feature shipment characteristics, such as value, tons, ton-miles, and average miles per
shipment by mode of transportation, commodities shipped, and destinations.
For more information:
http://www.census.gov/econ/www/se0700.html or 301-457-2788.
Transportation Annual Survey covers firms with paid employees that provide commercial
motor freight transportation and public warehousing services. Data collected include total
operating revenue and operating revenue by source, total expenses, percentage of motor carrier
freight revenue by commodity type, size of shipments handled, length of haul, and vehicle fleet
inventory.
For more information:
http://www.census.gov/econ/www/se0800.html or 301-457-2763.
Economic Census: Transportation Sector covers establishments that provide passenger and
freight transportation to the general public, government, or other businesses. Published data
include kind of business, geographic location, total operating revenue, annual and first quarter
payroll, and number of employees for pay period including March 12.
For more information:
http://www.census.gov/econ/www/servmenu.html or 301-457-2824.
Economic Census: Manufacturing Sector includes establishments that manufacture transportation
and transportation related products. Published data include geographic location, annual payroll,
inventories, capital expenditures, materials consumed, cost of materials, energy consumed, and
quantity and value of product shipments.
For more information:
http://www.census.gov/econ/www/manumenu.html or 301-457-4673.
Current Industrial Report - Truck Trailers covers establishments engaged in the
manufacture of truck trailers with a rating of 10,000 pounds or more per axle. This report
provides detailed monthly and annual data on the quantity and value of shipments of truck
trailers.
For more information:
http://www.census.gov/econ/www/ip4200.html or 301-457-4673.
Journey to Work provides data gathered from the 1990 Decennial Census. Data provided
include place of work, usual means of transportation to work, the number of persons who rode
(if in a car, truck, or van), the time leaving home for work, and the usual number of minutes
to get from home to work.
For more information:
http://www.census.gov/population/www/socdemo/journey.html or 301-457-2454.
Import/Export data can be obtained from the Census Bureau through the Data
Dissemination Branch of Foreign Trade Division. Data are collected under the Harmonized
Commodity Description and Coding System (Harmonized System).
For more information:
http://www.census.gov/foreign-trade/www/index.html or 301-457-2311.
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