Developing a Winter Severity Index to Improve Safety and Mobility

Adverse weather conditions are responsible for millions of vehicular crashes, thousands of deaths and billions of dollars in economic and congestion costs. Local, state, and federal agencies face increasing pressure to efficiently allocate resources in order to maintain accessibility to areal roadways during adverse weather events and must balance safety with stringent budget accountability. Many of these agencies utilize some type of performance or mobility metric to assess how well they are maintaining road access; however, such metrics often do not consider the overall severity of the weather conditions thus making it difficult to accurately assess success and failure for the agency. Some agencies that do consider weather severity in their performance metrics do not have an explicit index for weather conditions alone nor are the weather data used robust enough to understand the complex variability of most weather events. This research focuses on the development of an independent winter weather severity index for the state of Nebraska (NeWINS). The unique features of this index will include varying levels of complexity in order to more accurately capture the atmospheric conditions while simultaneously allowing for simplicity dependent entirely on the needs of the end‑user. The index will also bring in a climatological aspect to the index which has not been incorporated in many current indices.

First, an in-depth literature review was conducted to synthesize the current practices in developing winter severity index. The literature review helped the research team identify potential variables that need to be included in NeWINS. A rigorous data collection effort was undertaken to create a ten-year database in the state of Nebraska. Variables included, for example, are storm type (light snow, moderate snow or heavy snow event), air and road surface temperatures, and wind conditions. Meteorological data are obtained from the High Plains Regional Climate Center’s Automated Weather Data Network (AWDN), the National Centers for Environmental Information (NCEI) and the Meteorological Data Assimilation Ingest System (MADIS).  NeWINS is an event driven index that was derived for the Nebraska Department of Roads (NDOR) districts across the state. The index applied statistical analyses to the collected database and developed a mathematical formula that can be used to measure winter severity for each district. To validate the developed winter severity index, real‑time case studies will be conducted by applying the index to the 2016-17 winter season. While the 2016-17 season will not be completed by the time of this presentation, preliminary results and observations will be presented. 

It is expected that developing the winter severity index for the state of Nebraska would help both local and state transportation agencies to efficiently allocate resources during adverse weather events, while balancing safety, mobility, and available budget. Furthermore, the theoretical and practical contributions provided by NeWINS can be used by other local, state and federal agencies to improve their performance measurement practices.