Snow Event Effects on Interstate Highway Crashes

Abstract

This study compares snow event and equivalent nonsnow interstate vehicular crash rates and investigates weather-related elements that may contribute to crash occurrence during snow events. Vehicular crashes reported in the state of Iowa are examined on seven different sections of the interstate highway system during the 1995/1996, 1996/1997, and part of the 1997/1998 winter seasons. A geographic information system was utilized to combine crash records with weather and traffic count data to obtain the data set analyzed in this study. A significant increase was observed when winter snow event crash rates on the seven interstate highway sections were compared to crash rates on those same sections during equivalent nonsnow conditions. Crash, weather, and traffic data were further analyzed to identify snow event elements that play important roles in crash occurrence on interstate highways. The results of a Poisson model for crash frequency indicated that snow event duration, snowfall intensity, and average wind speed during snow events are important contributory elements. Additionally, traffic volume during snow events was also found to be a significant factor in crash occurrence.