Snowstorm Event–Based Crash Analysis

Abstract

This study investigated the impact of snowstorms on a roadway system and assessed winter maintenance efforts in improving highway safety from a macroscopic perspective. The Wisconsin State Trunk Highway System was used as the data source. An inverse relationship between deicing material consumption and crash counts during snowstorms is reflected in the analysis; it also implies multiple causes of snowstorm crashes. Primary factors considered in this research were the effects of various weather conditions and winter maintenance. Results showed a mixed influence of both the snowstorm severity and winter maintenance investment on road safety. That is, severity of the snowstorm in regard to duration, intensity, and wind speed increases traffic crashes and casualties with simultaneous consumption of more deicing materials and labors. The research also explicitly proves that a proactive winter maintenance effort significantly improves traffic safety. Temporal distribution of crash occurrence during a snowstorm shows that a large percentage of crashes occurred during initial stages of the snowstorms, probably because snow removal activities had not yet begun. The pattern is quite similar for state-maintained highways and local roads, except that in the second half of a snowstorm, a higher percentage of crashes occur on local roads than on state highways, possibly suggesting that the different level of maintenance and use of deicing materials may play an important role. Additional research is required to quantify the effects of deicing materials specifically, particularly in regard to application rate and frequency, on highway safety.