New publication provides insights on the impact of COVID-19 pandemic on road safety in California
SafeTREC Co-Director Offer Grembek, former Postdoctoral Researcher Praveen Vayalamkuzhi, and Applications Program Manager SangHyouk Oum have co-authored a book chapter, "Highway Crashes in California During the COVID-19 Pandemic: Insights and Considerations" as part of the new publication "Pandemic in the Metropolis: Transportation Impacts and Recovery." The book, edited by Anastasia Loukaitou-Sideris, Alexandre M. Bayen, Giovanni Circella, and R. Jayakrishnan, "offers an authoritative guide to the impact of COVID-19 on mobility and transportation in cities, includes case studies from California that illustrate lessons applicable to other metropolitan areas, and presents empirical, data-driven research work throughout."
This chapter describes the results of a short-term analysis of highway crashes in California during the first year of the COVID-19 pandemic. The pandemic has had an unexpected and abrupt influence on the demand for mobility. The effect of this was a drastic reduction in the level of activity on the roads. This level of activity defines the exposure of road users to crash risk and represents a focal variable in the sciences of traffic safety. The rapid rate of change in traffic that occurred during the pandemic, triggered a need to monitor highway safety at a higher frequency than what was previously common in traffic safety studies. We compiled data at the weekly level and analyzed six-week periods. Our analysis shows that the minor injury crash rate per 100 million vehicle-miles traveled (VMT) has gone down from 37.58 per 100 million VMT during the before period to 25.52 per 100 million VMT in the first period after the pandemic. This is a reduction of 32% in the minor injury crash rate per 100 million VMT. In contrast, the more severe and often catastrophic, major injury crash rate per 100 million VMT increased from 4.47 per 100 million VMT during the before period to 5.15 per 100 million VMT in the first period after the pandemic. This is an increase of 14.8% in the major injury crash rate per 100 million VMT. The resulting bifurcation across different crash severity levels indicates that although the overall crash rates dropped, the rate of catastrophic crashes (i.e., fatal and severe) got worse. The main implication of this finding is that a reduction in minor injury crashes does not necessarily correspond to a reduction in major crashes. These findings demonstrate that it is possible to reduce the overall crash rate without making the system safer in terms of fatal and severe crashes, and this should be considered when developing roadway safety programs.