The association between strengthened cellphone laws and police-reported rear-end crash rates

Reagan, Ian J. / Cicchino, Jessica B. / Teoh, Eric R. / Cox, Aimee E.
Insurance Institute for Highway Safety
August 2022

Introduction: Prior evaluations of the relationship between cellphone bans and crash outcomes show unclear effects. Advances in smartphone functionality have coincided with legislation to comprehensively define and prohibit cellphone use while driving. California, Oregon, and Washington enacted legislation (effective in 2017) to update earlier bans specific to handheld phone calls and texting. The current study evaluated the relationship between strengthening cellphone laws and the rates of rear-end crashes, a crash type sensitive to visual-manual cellphone use, in California, Oregon, and Washington.
Method: Negative binomial regression compared the change in monthly per capita rear-end crash rates in California, Oregon, and Washington before and after the law changes relative to the rates in two control states, Colorado and Idaho, during 2015–2019. Analyses examined (a) rear-end crashes with injuries in all three study states, including minor to fatal injuries; and (b) rear-end crashes of all severities in California and Washington, including property-damage-only crashes and crashes with injuries; Oregon was excluded from this analysis because of a 2018 change to its reporting criteria for property-damage-only crashes.
Results: Washington’s strengthened law was associated with a significant 7.6% reduction in the rate of monthly rear-end crashes of all severities relative to the rates in the control states. The law changes in Oregon and Washington were associated with significant reductions of 8.8% and 10.9%, respectively, in the rates of monthly rear-end crashes with injury relative to the rates in the control states. In contrast, California did not experience changes in rear-end crash rates of all severities or with injuries associated with the strengthened law.
Conclusion: The results of this study are mixed, with law changes associated with significant reductions in rear-end crash rates in two of the three study states. Differences in the wording of the laws, levels of enforcement, and sanction severity may help explain the divergent results. Practical application: The crash reductions in Oregon and Washington suggest that enacting legislation that comprehensively bans practically all visual-manual cellphone activity may have made the laws easier to enforce and clarified to drivers that handheld cellphone use is unacceptable in these states.