Digitally Distracted at the Wheel : Car Accidents and Smartphone Coverage

Digital distraction, or the myopic use of technology at the expense of longer-term utility, is of growing importance as technology with the potential to distract becomes ubiquitous. We examine the consequences of digital distraction among drives in California by examining the relationship between 3G coverage -- crucial for smartphone use -- and traffic accidents. To address the endogeneity between cell phone use and traffic accident propensity, we use the rollout of 3G cellular coverage on California's roads between 2001 and 2013. We construct road-level event studies computing the increase in traffic accidents when a road receives 3G coverage, controlling for traffic volume and road-level fixed effects. We use machine learning techniques to recover the historical relationship between road-level 3G coverage and cellular towers. We find that accidents rates increase by 1.1 percentage points when a road receives 3G coverage. The accidents most responsive to 3G coverage are non-severe crashes, those that take place in highly trafficked areas, and those driven by younger drivers. Back-of-the-envelope calculations suggest that 3G coverage resulted in 3,300 additional accidents in California alone, implying digital distraction may have meaningful aggregate consequences