Modeling the Impact of COVID-19 Interventions on Interstate Crash Rates Using Comparative Interrupted Time Series

Abstract

In the early stage of the severe acute respiratory syndrome (SARS)-CoV-2 coronavirus (COVID-19) outbreak in March 2020, a series of restrictions were released to minimize the exposure and spread of the communicable virus. These restrictions had significant impacts on the mobility and safety of transportation networks. The objective of this study is to assess the causal effects of the COVID-19 restrictions on traffic crashes on interstate highways. Specifically, compared with previous years, the study is to understand whether the COVID-19 outbreak has increased the rate of traffic crashes on Interstate 80 in Nebraska. A comparative interrupted time series (CITS) model was established to examine the week-to-week differences in traffic crashes before, during, and after the implementation of the COVID restrictive measures in Nebraska. Traffic crash data and traffic count data on Interstate 80 for 33 weeks, from Day 1 to Day 183, of 2020 were used. Meanwhile, the same periods of data in 2018 and 2019 were also included as a control group in the models. Results show that the COVID-19 restrictive measures were associated with significant, immediate, positive effects on crashes (i.e., crash reduction or mitigation) with no or minor injuries, crashes with single or two vehicle(s), and crashes with one injury involved. The findings contribute to the understanding of the impact of COVID-19 interventions on interstate highway safety when future outbreaks of COVID-19 or other pandemics become possible.