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7 TABLE 2 Climate-related items SUMMARY OF SNOW AND ICE CONTROL OPERATIONAL CONSIDERATIONS Frequency of Snow and Ice Events Low Moderate Climate is an issue that is primarily of importance in the High planning phase of snow and ice control operations. With minor exception, the various snow belt climate zones in North Amer- Severity of Winter Pavement Exposure Mild ica all experience similar types of winter weather events with Moderate mixtures of precipitation classes. The difference among the Severe climate zones is in the distribution of expected precipitation Wintertime Precipitation Type class events. Mountain climates, for example, see very few Rate freezing rain events; however, they may see more snow events Urban Influence with high accumulations. The bottom line is that all snow belt Small maintenance forces have to be prepared to deal with all types Medium Large of precipitation events. Industrial The ability to forecast and recognize the various types of Water Influence precipitation is extremely important. This influences to a Minor large degree the type of treatment, material choice, and mate- River Lake rial application rate. Ocean Site conditions, especially pavement temperature, snow/ Elevation/Large Scale Topography ice on the highway surface, and ice/pavement bond, are major Plain factors when deciding on material type and application rate. Rolling Mountainous Traffic characteristics appear to be less important than weather and site conditions; however, higher traffic volume and speed can displace snow and ice control materials from the high- way surface. TABLE 3 Precipitation definitions Light Rain. Small liquid droplets falling at a rate such that individual drops are easily detectable splashing from a wet surface. Include drizzle in this category. Moderate Rain. Liquid drops falling are not clearly identifiable and spray from the falling drops is observable just above pavement or other hard surfaces. Heavy Rain. Rain seemingly falls in sheets; individual drops are not identifiable; heavy spray from falling rain can be observed several inches over hard surfaces. Freezing Rain. When rain freezes upon impact and forms a glaze on the pavement or other exposed surfaces. Sleet (Ice Pellets). Precipitation of transparent or translucent pellets of ice, which are round or irregular in shape. Light Intensity of Sleet: Scattered pellets that do not completely cover an exposed surface regardless of duration. Visibility is not affected. Moderate Intensity of Sleet: Slow accumulation on ground. Visibility reduced by ice pellets to less than 7 mi (13 km). Heavy Intensity of Sleet: Rapid accumulation on ground. Visibility reduced by ice pellets to less than 3 mi (5.6 km). Light Snow. Snow alone is falling and the visibilit y is greater than 1/2 mi (0.9 km). Moderate Snow. Snow alone is falling and the visibility is greater than 1/4 mi (1/2 km) but less than or equal to 1/2 mi (0.9 km). Heavy Snow. Snow alone is falling and the visibility is less than or equal to 1/4 mi (1/2 km). Blowing Snow. When fallen snow is raised by the wind to a height of 6 ft (1.8 m) or more and is transported across a road. None. No precipitation or blowing snow. NOTE: An estimate can be made of the moisture content of falling snow as follows: 1 = powder snow 2 = ordinary snow 3 = wet/heavy snow a Definitions taken from Federal Meteorological Handbook (FMH) No. 1 (6).

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8 TABLE 4 Site conditions TABLE 5 Traffic conditions Area Type Traffic Volume Urban Very low Suburban Low Rural Medium Special Highway Segment Areas High Hills Very high Curves Commercial Vehicle Mix Grades Low Intersections Moderate Bridges High Sags Ramps Vehicle Speeds Crosslopes Low Weaving Areas Moderate Narrowings High Roadway Widenings Elevated Roadways Pavement Surface Types Tangents Shadings from Solar Influence Forest/vegetation Buildings/structures Cuts Pavement Conditions Temperature Ice/pavement bond Frost or thin ice Slush, loose snow, packed snow, thick ice