This methodological and analysis report outlines the procedures and findings for the fifth annual wave of the “Observational Survey of Cell Phone and Texting Use among California Drivers Study,” conducted by Ewald & Wasserman Research Consultants (E&W) on behalf of the California Office of Traffic Safety (OTS) and the Safe Transportation Research and Education Center (SafeTREC) at the University of California, Berkeley. This combined report describes E&W’s survey research and data collection procedures implemented for the fifth wave of this longitudinal study, which collected data of a statistically representative sample on drivers’ distracted driving behaviours, including cell phone and other electronic device use. The overall study design included the observation of California vehicle drivers at controlled intersections such as traffic lights and stop signs-using a data collection protocol similar to the National Occupancy Protection Use Study (NOPUS) methodology published by the National Highway Transportation Safety Administration (NHTSA) on electronic device use by drivers in their Traffic Safety Facts publications, DOT HS 811 372 and DOT HS 811 361. The data collection plan also incorporated sections of the methodological outline of the Seat Belt Survey Regulation for Section 157 Surveys: 23CRF Part 1340, published by NHTSA. In the 2015 observations, the majority of drivers (73.0%) drove alone, and 22.0% had one passenger in the car. The increase of drivers driving alone since 2014 (4.8%) and the decrease (3.5%) of drivers driving with one passenger is significant (Table 13). In total, 5.4% of all observed drivers displayed distracted driving due to device use, compared to 3.8% in 2014, a significant increase of 1.6% (Table 16). Compared to 2014, holding a phone to the ear significantly increased by 0.6%, the use of headsets/Bluetooth devices increased significantly by 0.5%, and manipulating a hand-held device while driving increased significantly by 1.1% (Table 17). There is no significant difference between males and females in the rate of distracted driving, but there is a 1.7% significant increase of male driver device use compared to 2014 (Table 18). The difference in device use among the areas defined as rural, urban, or suburban is significant, with the highest observed device use in suburban areas (7.3%) and the lowest in rural areas (3.7%). Compared to 2014, the increase of electronic device use while driving was significantly higher in suburban areas (a 2.7% increase, Table 19). Overall, younger drivers are displaying significantly more electronic device use, with 7.0% of all 16-24- year-olds displaying this behavior. There is also a notable increase in the device use in all age groups since 2014, with a significant increase of 1.7% for 25-69-year-old drivers (Table 21). Distracted driving due to electronic devices use by time of observation does not show any significant differences among the rush hour, weekend, and all other times of data collection. The 1.8% increase in electronic device use since 2014 during rush hour as well as the 1.6% increase at other times except weekends is significant (Table 23). In 2015, there is a significantly higher rate of 16-24-year-olds being observed holding a phone to their ear while driving (3.5%) compared to the other age groups (Table 24). In comparison to the 2014 data, there is a significant 3.7% decrease among 16-24-year-olds in the manipulation of electronic devices while driving. At the same time, there is a significant increase in the observed manipulation of hand-held devices among 25-69-year-old drivers of 1.5% since 2015 (Table 24). The region variable–North, South, and Central California–and the observation of drivers talking on a headset or Bluetooth device shows significant differences with a lower observation rate among Central region drivers (Table 30). The increase of headset or Bluetooth use in Southern California by 0.7% compared to 2014 is significant as well. Overall, there are significant differences in the incidence of distracted driving and the number of passengers in the car. Of drivers alone in a car, 6.2% were observed using an electronic device while driving; that percentage is reduced with more passengers in the vehicle (Table 33). There has also been a significant 1.8% increase in instances of distracted driving due to device use for drivers alone in the car (Table 33). Use of hands-free devices is difficult to identify in observational studies because the device may not be visible to the observer. Consequently, "Talking with headset/Bluetooth" is likely to be underestimated at the observed level of 1.4% in 2015. The National Highway Traffic Safety Administration (NHTSA) has developed a methodology to correct for this difficulty. The correction raises the hands-free usage from 1.7% to 3.3%, and the overall cell phone usage rate from 7.3% to 9.2% (see also Appendix B). (Author/publisher)
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