More about Surface Temperature
Surface temperature is a far better indicator than air temperature of whether precipitation will cause any problems on winter roadways. What really makes the difference between a wet road and an ice or snow covered road is the surface temperature, along with any anti-icing or deicing treatments that have been applied. The surface temperature helps the Iowa DOT Maintenance Division employees determine the amount and type of treatment to use to maintain or restore the highway to normal winter driving conditions.
Surface temperatures are not easy to predict because there are a lot of factors that influence the surface temperature of a roadway. Some of the factors are:
  • Subsurface temperature
  • Air temperature
  • Amount of thermal gain from sunlight; is it day or night, cloudy, or sunny?
  • Type of structure; is the surface a bridge or roadway?
  • The surrounding terrain; is it shaded by a grove of trees, in a valley or on a hill?
  • Roadway orientation & composition; is the lane sloped toward or away from the sun, what is the type and depth of pavement?
    • Anti-icing

    Anti-icing is the snow and ice control practice that has a goal of preventing the formation or development of bonded snow and ice by timely applications of a freezing point depressant.

    Deicing

    Deicing is the snow and ice practice of removing bonded snow and ice from the roadway using freezing point depressants or mechanical methods. It is typically associated with using freezing point depressants such as salt or calcium cloride to melt through a layer of snow and ice to get to the underlying surface, or by the use of plows or ice blades to remove snow and ice.

    Freezing point depressant

    A freezing point depressant is any deicing chemical that lowers the freezing point of water. The most common freezing point depressants used in the United States are sodium chloride (salt), calcium chloride and magnesium chloride.


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