Effects of macroeconomic conditions on the incidence of motor vehicle accidents

The economic recession has been suggested as a probable cause of the significant decline in traffic casualties in the U.S. in the early 1980s. The present study was designed to identify the underlying relationship between changes in economic conditions, as reflected in the rate of unemployment, and motor vehicle crash involvement. The potentially intervening influence of vehicle miles traveled was also examined. ARIMA and dynamic regression time-series modeling procedures were used to assess the direction, magnitude, and lag structure of the relationships. Results revealed a significant concurrent inverse relationship between the rate of unemployment and the frequency of crash involvement, and a significant lag 1 positive relationship between these two variables. Vehicle miles traveled was not a significant intervening influence between un-employment and crash involvement. Summing the concurrent and lagged effects indicated a net negative relationship between unemployment and crash involvement. However, the magnitude of the effect is quite small, accounting for only a small portion of the total decline in traffic casualties in recent years.