Recent Major Improvements in Road Safety in the U.S.: Changes in the Frequency of Crashes or the Severity of the Outcome of Crashes?

Abstract

This study introduced a new methodology for evaluating the relative contributions of the changes in the frequency of crashes and the severity of the outcome of crashes to the recent large improvement in road safety in the U.S. The approach is based on a parallel examination of changes in variables for all crashes and for fatal crashes only. The change for all crashes provides an index of the change in the frequency of crashes; the difference between the change in the frequency of fatal crashes and the change in the frequency of all crashes provides an index of the change in the severity of the outcome of crashes. The specific analysis that was performed using this new methodology involved examining the changes from 2005 to 2009 in 11 selected variables common to both the GES database (all crashes) and the FARS database (fatal crashes only). The main result is that from 2005 to 2009 there were reductions in both the frequency of crashes and the severity of the outcome of crashes. The obtained patterns of change for the 11 examined variables are consistent with the known changes in factors such as the economic conditions (resulting in less driving, and different proportions of leisure and nighttime driving), installation of active-safety technology (e.g., electronic stability control), installation and quality of passive-safety technology (e.g., airbags), licensing of young drivers, and driver distractions.