Snowstorm Event-based Crash Analysis

This study investigated the snowstorm impact on Wisconsin state highway system and assessed the winter maintenance effort in improving highway safety from a macroscopic perspective. Though the inverse relationship between the de-icing material consumption and the crash counts during the snowstorms is not reflected in the analysis, it implies that causes of snowstorm crashes are multifold. The following main factors were investigated: weather, human factors, and winter maintenance. The results showed a mixed influence of both the snowstorm severity and winter maintenance investment on road safety. In other words, the severity of the snowstorm in terms of duration, intensity, and wind speed increases traffic crashes and casualties, while at the same time consuming more de-icing materials and labors. The research also explicitly proves that a proactive winter maintenance effort will significantly improve traffic safety. The temporal distribution of the crash occurrence during a snowstorm shows that a large percentage of crashes occurred during the initial stages of the snowstorms, likely because snow removal activities had not yet commenced. The pattern is very similar for both state-maintained highway and local roads except that in the second half of a snowstorm, higher percentage of crash occurred on local roads than that of the state highways possibly suggesting that the different level of maintenance and the use of deicing materials may play an important role. Additional research is required to specifically quantify the effects of de-icing materials, particularly with regards to application rate and frequency, on highway safety.