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Winter roadway operations, commonly known as snow/ice control operations, are one of the most critical functions of state, provincial and local transportation agencies in cold regions. These operations aim to provide safety and mobility by timely and effective application of materials and plowing. The most common materials used are salt (sodium chloride, solid and brine), magnesium chloride-based, and calcium chloride-based deicers, agro-based additives and blends, and abrasives, with the specific choice and application method and rate dependent on temperature, precipitation type, level of service goals, budget, and environmental sustainability. Best practices of material application are designed to apply the right type and amount of materials in the right place at the right time. A companion document to this report, the “Material Application Methodologies Guidebook,” synthesizes the use of materials, including application strategies, application rates, and application equipment. This report documents the literature review and agency interviews that were conducted to assemble the information for the Guidebook.

Extremely cold winter storms (below about 10°F) bring about different considerations for taking care of roads than warmer winter storms, where granular salt and salt brine are cost-effective measures of melting snow and ice when used in combination with other operations (e.g., plowing). At temperatures lower than about 10°F, either extremely large quantities of salt are needed or no amount of salt can melt snow or ice pack. Best practices for using chemicals during extremely cold winter storms include: waiting until the end of the storm, using deicers in daylight hours only, mixing salt with MgCl2, CaCl2, and/or agriculture by-products, and using high application rates. Despite their environmental and hidden costs (air pollution, sedimentation, spring cleanup & disposal), abrasives are frequently used during extreme temperatures to provide temporary traction. Best practices for using abrasives during severe cold includes prewetting with liquid deicers (although not plain salt brine-it may freeze) or hot water. Innovative strategies continue to be tested at severe temperatures, including conductive pavements and geothermal systems, which have demonstrated to be potentially effective tools.