Rural and urban traffic fatalities, vehicle miles, and population density

The purpose of this study was to evaluate the effect of population density on the rates of motor vehicle mortality in rural and urban areas, while controlling for vehicle miles traveled (VMT). Rural and urban data for traffic mortality, VMT, and population were obtained for each state from the Federal Highway Administration for 1998-2000. Linear regression was used to estimate the effect of population density, VMT per capita, southern location, and presence of a trauma system on mortality. Variation in rural mortality rate (per 100,000 population) was proportional to rural VMT per capita, but population density and southern location were also independent predictors, together accounting for 91% of this variation. Variation in urban mortality rates was not affected by population density, but urban rates were also higher in the south. The exposure-based rural mortality rate (deaths per 100 million VMT) was inversely proportional to population density, which along with southern location explained 41% of the variation from state to state. The presence of a state trauma system did not measurably affect mortality. After controlling for VMT and southern location, state population density was a moderately strong predictor of rural but not urban traffic mortality rates.