Influences on passenger vehicle casualty accident frequency and severity: unemployment, driver gender, driver age, drinking driving and restraint device use.

A correlational examination of 84 consecutive months of data on the frequency and severity of passenger vehicle casualty traffic accidents, unemployment rates, drinking driving, restraint device use and the driver demographics of driver age and driver gender suggested the following: Increases in unemployment levels remove young male drivers from the driving population, which in turn reduces the frequency of drinking driving and increases the proportion of restraint device use in this population. These changes combine to reduce both the frequency of casualty accidents per million driven kilometers and the severity of these accidents. However, the apparent relationship between changes in restraint device use and the frequency and severity of casualty accidents, and the apparent relationship between changes in drinking driving and the frequency of casualty accidents can be, to a great extent, a function of unemployment-driven changes in driver demographics.