Winter Severity Index: Using Road Weather Information System Data to Improve Preparedness for the Pennsylvania Department of Transportation

Road Weather Information System (RWIS) data provides multifaceted weather information to Departments of Transportation for many states and even the Federal Highway Administration. For the Pennsylvania Department of Transportation (PennDOT) Winter Operations Section this data plays a major role for roadway conditions in the winter season. RWIS data from 71 sites across the state provides coverage for winter storms regarding snowfall, ice accumulation, major snowfall events, and duration of events. Using the RWIS data from the previous three winter seasons, a scale was created to help better prepare the state for the 2019-2020 winter and winters to come. The RWIS data that is used within this scale is the amount of snowfall, duration of snowfall, amount of frozen precipitation, and duration of frozen precipitation. This scale was called the Winter Severity Index (WSI) and is calculated for every day that there is a winter event or frozen precipitation. WSI varies from mild to extreme depending on the type of precipitation and duration of the precipitation accumulated, the more accumulation, the more extreme the event. The amount of salt used per county in each season was then compared to the WSI to determine which counties of Pennsylvania were best prepared with their salt usage and where improvements needed to be made. It was found that 15 counties in Pennsylvania were ill-prepared based on their salt usage. Two current improvements, watching how much salt is being applied to the roadways and only applying salt when absolutely necessary are currently being made to make sure that these counties are better prepared for upcoming winters.