INTRODUCTION: Distracted driving resulting from secondary task engagement is a major contributing factor to teenage drivers' crash risk. This study aims to determine the extent to which visual inattention while engaging in distracting secondary tasks contributes to teenage drivers' crash risk.
METHODS: Real-world driving data were collected from a cohort of 82 newly licensed teenagers (average age 16.48 years, SD=0.33) recruited in Virginia. Participants' private vehicles were equipped with data acquisition systems that documented driving kinematics and miles driven, and made video recordings of the driver and driving environment. Data were collected from 2010 to 2014 and analyzed in 2017. The analysis of secondary task engagement was based on 6-second video segments from both crash and random samples of normal driving.
RESULTS: Of a wide range of secondary tasks, only manual cellphone use (OR=2.7, 95% CI=1.1, 6.8) and reaching/handling objects while driving (OR=6.9, 95% CI=2.6, 18.6) were associated with increased crash risk. Drivers' duration of eyes off the road accounted for 41% of the crash risk associated with manual cellphone use and 10% of the risk associated with reaching/handling objects while driving.
CONCLUSIONS: Secondary tasks vary in the risk they introduce to the teenage driver. Manual cellphone use and reaching for objects were found to be associated with increased crash risk. These findings objectively quantify the effect of visual inattention resulting from distracting secondary tasks on teenage drivers' crash risk. Teenage drivers may benefit from technologic and behavioral interventions that will keep their eyes on the road at all times and discourage engagement in distracting secondary tasks.