The Pooled Fund Study (PFS) Maintenance Decision Support System (MDSS) is a toolset that provides objective guidance to winter maintenance personnel on the best treatment options for maintaining required levels of service in the face of adverse road weather conditions. The PFS MDSS applies a sophisticated pavement model working within agency operating constraints to arrive at optimal treatment strategies. Thus far, the PFS MDSS has primarily been applied as a short term prognostic tool used to predict future road conditions in response to expected weather conditions and candidate maintenance actions. This project is an extension of this product into a diagnostic tool by using archived weather data in combination with PFS MDSS software to generate an objective assessment of expected road conditions and maintenance resource utilization throughout entire winter seasons. These assessments will be compared to the maintenance actions that were actually performed in selected test areas in order to establish the level of correlation with actual resource utilization. A Winter Severity Index will then be derived that is based upon the scientifically modeled response of roadways to weather and maintenance activities rather than on weather conditions alone. Such an index is useful to winter maintenance agencies as both an objective metric for agency performance as well as for justification of annual variances in agency winter maintenance costs.