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Over time, VIUS captures comprehensive data on the usage of the United States’ nongovernmental commercial and private truck fleet. Prior to the 2002 iteration, VIUS was fielded every 5 years, offering trending opportunities between surveys. After the 2002 VIUS, nearly 20 years passed until the next deployment in 2021. This hiatus introduced unique challenges and opportunities for survey improvement—both in survey methodology and survey questionnaire design—to allow for capturing information on the adoption of advanced vehicle technologies as well as vehicle evolution. 

This report (Differences Between the 2002 VIUS and 2021 VIUS) lists and compares key analytical and methodological differences between the 2002 VIUS and 2021 VIUS—particularly, with respect to data fields and survey methodologies. The main findings include the following: 

• Compared to the 2002 VIUS, the 2021 VIUS included 31 new data fields and series. These new fields include logical follow-up questions as well as questions related to new technologies and administrative priorities. In addition, 28 questions in the 2021 VIUS included nonresponse validation options (e.g., “none of the above” or similar). 
• Several methodological changes exist between the 2002 VIUS and 2021 VIUS that can impact statistical comparability between the two surveys. These changes include differences in the primary survey instrument (e.g., paper for the 2002 VIUS versus online tool for the 2021 VIUS), survey design, weighting plans, geographic coverage, and response rates. 
• Considering the differences between the data fields and survey methodologies of the 2002 VIUS and 2021 VIUS, comparison between the two surveys should be limited to contextual and historical applications.