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Directions in Highway Safety Cover - Summer 2011 Download Newsletter pdf
[2 MB, 12 pgs.]

Summer 2011 | Vol. 13 | No. 2

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CDC Compares Self-Reported and Observed Seat Belt Use

In a recent study published in Injury Prevention, the Center for Disease Control (CDC) compares self-reported and observed seat belt use. The main finding is that self-reported seat belt use is no longer higher than observed use. CDC concluded that, “As seat belt use has increased over time, measures of self-reported and observed use have converged, and any upward bias in self-reported use due to social desirability has substantially declined.” Dr. Aybaniz Ibrahimova, a CDC fellow, conducted the study. It replicates an original study published in Injury Prevention in 1996. CDC compared state-level seat belt use from the Behavioral Risk Factor Surveillance System (BRFSS) to the state-level observational survey results. The BRFSS estimates represent people who report always wearing their seat belt when riding in a vehicle.

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A couple of findings are particularly interesting. First, the BRFSS and observational estimates from the same states were closer to each other in the states with primary laws. Also, four states stood out as outliers. It appears that people in Louisiana and Massachusetts over-reported and people in North Dakota and South Dakota under-reported seat belt use to BRFSS. In the case of North Dakota and South Dakota, a higher proportion of residents reported part-time belt use compared to other states. CDC speculates that the observational surveys are picking up some of these part-time users. It is also likely that the rural population in the Dakotas is underrepresented in the observational survey, which may contribute to the disparity between the BRFSS and observed estimates. The new seat belt observation methodology may provide a remedy to this problem. CDC notes that they do not know what might contribute to the disparity in Louisiana and Massachusetts, but the Agency looked back to previous data and saw the same pattern.

State BRFSS Belt Use State Observational Belt Use
Louisiana 89.2 % 75.5 %
Massachusetts 80.4% 66.8 %
North Dakota 59.2 % 81.6 %
South Dakota 59.7 % 71.8 %