An Analysis of the Relationship Between Rainfall and the Occurrence Of Traffic Accidents

Abstract

Analysis of METROMEX rainfall data and traffic accident reports for seven southern Illinois cities within the area of the St. Louis precipitation anomaly revealed a statistically significant increase in the number of accidents reported during rainy periods compared to non-rainy periods in each city. When observations for the cities were combined, a statistically significant linear trend between mean number of accidents and amount of rainfall was identified. A measure of accident severity, computed by the mean number of injuries for each accident, increased in some of the cities when it rained but decreased in others. None of these increases or decreases were statistically significant. It is speculated that the St. Louis precipitation anomaly probably results in an increase in the occurrence of traffic accidents in the area of its effect.