Examining the causal effects of distracted driving on crash injury severities

Abstract Distracted driving is a critical factor affecting traffic safety. Although previous studies have been devoted to exploring the effects of driver distraction on crash risks, few of them are available to quantitatively analyze the impacts on crash injury outcomes. Thus, the study aims to examine the effects of distracted driving on injury severities for both at-fault and not-at-fault drivers. Propensity score matching method is adopted to balance the covariates between the data sets of distracting and normal driving, so as to avoid the potential effects caused by confounding factors. Average treatment effect is calculated to quantify the impacts of distraction on specific injury severity levels. The results indicate that 1) drivers are inclined to be distracted in the scenarios of roadways with higher speed limits, non-peak hours, intersection area, sunlight, cloudy weather, young and female drivers, and heavy vehicles; 2) for the at-fault drivers, the distraction appears to increase the occurrence probabilities of both fatal and injury crashes; and 3) as for the not-at-fault drivers, the distraction can lead to the increase of possible injury crashes. The study confirms the significant causal effects of driver distraction on crash injury severities and serves to propose the countermeasures to reduce the distracted driving.