Naturalistic Driving Study: Descriptive Comparison of the Study Sample with National Data (2015)

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1Data from Project S31, Naturalistic Driving Study (NDS) User Support and Data Dissemination, of the second Strategic Highway Research Program (SHRP 2) are meaningful only if the relation of the drivers, vehicles, roads, and crashes in the data to the drivers, vehicles, roads, and crashes in the United States is understood. However, this relation may vary for different research questions. This report illustrates how the data relate to the country as a whole across several key dimensions. SHRP 2 data are fairly inclusive of the nation in many respects. The counties from which partici- pants were drawn, when aggregated, include a wide range of geographical features, roadways, and climates. Similarly, the SHRP 2 vehicle fleet includes all the national fleet’s light vehicle types and most of its light vehicle makes, although it is biased toward recent model years. SHRP 2 drivers range in age from 16 to 95, with younger and older drivers oversampled. Two SHRP 2 crash rates were calculated: a lower “confirmed” estimate, using the crashes known to have been reported, and an upper “possible” estimate, using the crashes judged to meet the police-reportable threshold. The confirmed SHRP 2 crash rate is slightly below the national police-reported crash rate, and the pos- sible SHRP 2 rate is substantially above the national rate. However, the SHRP 2 NDS sample is not representative of the national driving population. Analysts who wish to use Project S31 data to make comparisons with a national population of some characteristic, such as driver age, will need to weight the SHRP 2 data to match the national distribution of that characteristic. This report provides an example of weighting by driver age and gender. The information presented in this report should be helpful in using and interpreting SHRP 2 NDS data to illuminate how drivers behave in real-world settings, especially those moments leading up to and during crash-related events. Executive Summary