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16 TABLE 7 Strategies and tactics and LOS expectations Within-event LOS After-event LOS Strategies and Tactics Low Medium High Low Medium High Anti-icing X X Deicing X X X X Mechanical X X Mechanical and Abrasives X X Mechanical and Anti-icing X X Mechanical and Deicing X X X X Mechanical and Prewetted X X Abrasives Anti-icing for Frost/Black Ice/ X X Icing Protection Mechanical and Abrasives Containing > 100 lb/LM of X X X X X X Chemical Chemical Treatment Before or Early in Event, Mechanical Removal During Event, X X and Deicing at End of Event Mechanical and Anti-icing Mechanical and Abrasives Containing More than 100 lb/LM of Chemical Timely mechanical removal of snow/ice within an event, in conjunction with an overall anti-icing strategy, will pro- "Rich" abrasives/chemical mixtures containing more than duce the highest possible LOS within and after events. 20 percent chemicals by weight have been used for many years. They are capable of providing all ranges of LOS, depending on pavement and weather conditions. The LOS provided is generally in proportion to the amount of chemi- Mechanical and Deicing cal in the mix and the application rate. Research has shown that to produce a high LOS, a strategy of using chemicals Mechanical removal in conjunction with a deicing strategy alone will be more effective and less costly than using mix- within an event will produce low to medium LOS within and tures of chemicals and abrasives. after winter weather events. This primarily results from con- trolling the depth of loose snow and ice on the roadway. Chemical Treatment Before or Early in an Event, Mechanical Snow/Ice Removal During an Event, and Deicing at the End of an Event Mechanical and Prewetted Abrasives This is a hybrid strategy suitable for lower priority roads Mechanical removal plus treatment with abrasives that that produces a medium after-event LOS for a small chemi- have been prewetted with liquid chemical is capable of pro- cal investment. The initial chemical application seems to pre- ducing low within- and after-event LOS. Pavement temper- vent a strong ice/pavement bond. This, in conjunction with atures above 32F that will not allow ice/pavement bond may the later chemical application and any solar pavement warm- allow higher LOS to be achieved. Limited research shows ing, leads to a fairly quick recovery. This is particularly effec- prewetting abrasives might produce a slightly higher LOS tive when the chemicals are placed in a narrow band around than a stockpile mix alone. the center of a two-lane crowned roadway. TREATMENT SELECTION Anti-icing for Frost/Black Ice/Icing Protection When selecting treatments, the most important considera- Use of a liquid ice control chemical for pretreating areas tion is LOS goals. Depending on a variety of factors, the susceptible to frost/black ice/icing that may occur in the goals may change during an event. absence of precipitation is a proven effective anti-icing tac- Every snow and ice control treatment should be individ- tic that prevents ice formation. Since the ice does not form, ually designed to produce an effect that is consistent with the LOS is always high. the LOS goals, weather conditions, pavement conditions,

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17 and available resources of the moment. Weather and pave- information on weather and pavement conditions plus having ment conditions are continually changing and may require an understanding of the LOS goals and capabilities of avail- tactical adjustments. LOS goals may be changing with the able resources. These resources include snow and ice control time of day and pavement conditions. Available resources strategies and tactics, materials, equipment, and manpower. may be changing with equipment breakdowns and manda- Attachment 1 provides recommended guidelines for using tory personnel rest periods. road and weather information to make snow and ice control The actual formula or process for making wise and appro- treatment decisions. Chapter 8 provides recommended oper- priate treatment decisions is simple. It involves using timely ational guidelines for winter maintenance field personnel.