A Salt Inventory Management Strategy for Winter Maintenance

Expenditures for winter maintenance materials total nearly $20 million annually in a mid-western USA state. During an average winter the State Department of Transportation (DOT) uses approximately 666,000 tons of rock salt and has the capacity to store roughly 617,000 tons of material at various locations. Each year, each county in this Mid-western state establishes a contract through DOT with a salt vendor before the winter season and that vendor supplies all garages in the county for the entire season. In order to develop a systematic salt inventory management strategy that achieves the statewide goals for safety, ordering guidelines for each county that specify when to order and how much to order based on an (R, S)-inventory guideline is developed. These guidelines take into account the history of usage and deliveries in a county, as well as the monthly variation in usage. The inventory guidelines developed for the different areas of the state are based on a weather regression model for the major cities/counties in the state relating usage to weather. The guidelines were tested and refined using a computer simulation methodology. The resulting guidelines are compared to the state’s current DOT guidelines for inventory, as well as compared to the county storage capacities to develop recommendations.