Farmer, Charles M.
Insurance Institute for Highway Safety
The objective of this study was to determine the extent to which the 2015 increase in U.S. traffic fatalities is consistent with historical relationships between the economy and fatalities and to project the trend in fatalities through 2024 based on those relationships.Methods:
Linear regression was used to model the number of vehicle miles traveled (VMT) during 1990-2015 as a function of calendar year and the unemployment rate. Then Poisson regression was used to model annual traffic fatality counts as a function of year, the unemployment rate, and miles of travel. Projections of future unemployment rates by the Bureau of Labor Statistics were used to project future miles traveled and traffic fatality counts.Results:
VMT was estimated to increase by an average 1.5% per year if the unemployment rate was unchanged. For each unit increase in the unemployment rate, the VMT declined by an average 1.8% per year. Fatalities were estimated to decline by approximately 2.2% per year if the VMT and unemployment rate were unchanged. Each 1% increase in VMT was associated with a 0.96% increase in fatalities. Finally, after accounting for the effects of time and VMT, for each unit increase in the unemployment rate fatalities declined by 2.1%.Conclusions:
The sharp increase in U.S. traffic deaths in 2015 can be tied primarily to the improving economy, although other lesser factors also were involved. However, the long-term decline in traffic deaths seems to be continuing. Assuming a more gradual improvement or leveling of the economy, it is projected that there will be about 34,000 traffic deaths in the U.S. in the year 2024.