operations, road capacity, and road safety. This report provides a roadmap for moving these concepts to reality.

METEOROLOGICAL CONDITIONS THAT INFLUENCE THE ROADWAY ENVIRONMENT

Nearly all weather conditions affect the roadway environment in some way, typically by affecting visibility, surface traction, or maneuverability of vehicles. Winter weather conditions, including snow accumulation, freezing rain, icy surfaces, and blowing snow, have received the most attention by the transportation community because they can significantly impair the operability of the roadway system over a large region (Figure 1-1). In 2001 110,072 crashes occurred on snowy or slushy roads; consequently, over 1,100 people were killed and nearly 95,000 people were injured. An additional 183,377 crashes occurred in 2001 during snowfall or sleet; nearly

FIGURE 1-1 Traffic on a snowy day. SOURCE: Curt Pape, Minnesota Department of Transportation.



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