Safety Impacts of Road Weather Information Systems (RWIS)-A State-wide Cost Effectiveness Case Study

Road Weather Information Systems (RWIS) have long been favoured by many North American and European highway authorities as they provide real-time and near-future road condition information during the winter months. Information disseminated by individual RWIS stations is collectively used to efficiently mobilize winter road maintenance operations, promoting safe travel during adverse weather events. However, the high installation and operational costs of RWIS oblige transportation authorities to quantify their cost-effectiveness, particularly in improving traffic safety. Therefore, this study addresses the research question "Has RWIS implementation led to a significant reduction in winter weather collisions, making roads safer for commuters?" by implementing one of the most widely adopted methods used in traffic safety studies; namely, the before-and-after Empirical Bayes approach. For the evaluation, Geographic Information Science (GIS) -based techniques were used to prepare intensive datasets. Further, Safety Performance Function and Yearly Calibration Factors were locally calibrated using this large-scale spatial data, where network-based service area analysis using GIS played a crucial role in selecting treatment and reference sites. The case study results of seven stations in Iowa, U.S., showed inclement winter collision reduction ranging from 31.53% to 88.23%. This study further answered another research question, "Is RWIS a cost-effective safety countermeasure?" by conducting a detailed economic analysis and estimating benefit-cost ratios ranging from 7.51 to 34.16. The results indicate that RWIS is an economically viable safety countermeasure.