Developing a Winter Severity Index: a Critical Review

Severe weather conditions, especially snow and ice during the winter season, threaten surface transportation nationwide and impact roadway safety and mobility. In particular, snow and ice decrease pavement friction and vehicle maneuverability, causing slower speeds, reducing roadway capacity, and increasing crash risk. These stressors make road maintenance during winter a pressing concern. The annual cost of winter highway maintenance in the United States is approximately $2.3 billion; however, evaluating the performance of such maintenance activities is difficult. To address this difficulty, the storm's severity should be standardized to measure performance against storm severity. Studies have been conducted to develop winter severity indices that can measure the difficulty in maintaining the targeted level of service due to storms in North America. Given the diverse approaches catalogued within these studies, there is a critical need for a comprehensive and organized literature synthesis to summarize existing approaches and to provide guidance for future winter severity index–development. To address this objective, this study investigated existing winter weather severity indices and classified the indices into different groups based on their development process and their similarities. In total, 19 winter severity indices were identified and sorted into seven groups. Subsequently, the key meteorological variables (i.e., temperature, snow, wind, and freezing rain) that have been used by other transportation agencies to develop winter severity indices were identified and explained in detail. Finally, the relevance of previous winter severity indices to future winter severity index–development was discussed and meteorological variables that can potentially be incorporated into the model were identified. This literature synthesis consolidates the current knowledge regarding winter severity indices and provides future guidance for developing an effective and reliable winter severity index.


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  • Accession Number: 01700308
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Feb 14 2019 3:06PM