Nineteen state highway locations around south-central and southwestern Minnesota were evaluated during winter 2019-20 for the application of deicer “hot shots,” extra levels of salt or other chemical treatments used to deice roadways and maintain roadway driving levels of performance. Locations were selected based on previous recordkeeping that indicated difficult winter driving conditions including drifting, blow ice formation, ice fog (black ice formation), roadway shading, and exposed bridge decks. Highways selected were representative of low-traffic-volume roadways classified as rural commuter, primary, and secondary roads. Deicer application amounts were gathered from AVL measurements made onboard plow trucks. Local and regional weather conditions were measured. A total of 909 application passes by plow trucks were found for the nineteen locations of study for winter 2019-20. Hot-shot treatments were observed to comprise 28% of the total treatments.
Hot-shot treatments were observed, but neither at the proportions nor in the patterns expected for the studied situations of winter roadway difficulty. Operator judgment appeared to be much more important than any other defined factor. In the balance of winter driving level of service and costs, with costs not only measured in money but also in labor, equipment and environmental impact, perhaps the best investments will be in enhanced operator training and the sharing of experience; roadway and weather information systems; and public education and the management of expectations. This report can be downloaded from the Minnesota Department of Transportation web site at https://www.dot.state.mn.us/research/reports/2020/202032.pdf