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A direct observation study of nighttime seat belt use was conducted in Indiana surrounding the Click It or Ticket (May Mobilization) activities. Two nighttime full statewide surveys were conducted, one in April and the other in June 2006. For this study, the hours between 9:30 p.m. to 5:45 a.m. were defined as nighttime. This time included all hours of darkness between the end of twilight in the evening to the beginning of twilight in the morning during June 2006 in Indianapolis, Indiana. Observations were conducted at roadway intersections, freeway entrance and exit ramps, and road segments using specialized night vision equipment. The nighttime survey waves were designed to coincide with daytime waves already planned for Indiana by the Center for the Advancement of Transportation Safety, and the Indiana Criminal Justice Institute.

The first objective of the study was to determine if there was a differential change in daytime versus nighttime seat belt use surrounding the mobilization activities. A secondary objective was to compare daytime to nighttime seat belt use to see if there was lower seat belt use at night, as has been found by others.

The comparisons across the mobilization period revealed a statistically significant increase during the day (79.7% and 84.3%, respectively), and a statistically significant decrease at night (79.0% and 74.0%, respectively). These results suggest that the daytime mobilization activities had a positive effect on daytime belt use, but no effect on nighttime belt use. There is no obvious reason for the belt use decrease observed at night during this period.

Comparisons were also made between daytime and nighttime belt use within each time period(pre- and post-mobilization). No differences were observed during the pre-mobilization wave, while a statistically significant difference was observed during the post wave. This difference is jointly attributed to the differential effect of the mobilization activities on daytime and nighttime belt use across the mobilization period, and the decrease observed within the nighttime waves.

Finally, many of the common daytime trends in belt use (i.e., lower belt use for males than females) were also found at night, with the exception of the effect of age (typically younger motorists buckle up less often) and seating position (typically drivers display higher belt use).

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