There are two main reasons for this: Most bridges use steel and concrete in their construction, both of which are good heat conductors. This means that any heat the bridge has moves through the bridge structure to the surface where the heat is lost to the air. Roads on the other hand are mostly made from asphalt, which is a poor conductor of heat - so experiences a lower rate of heat loss. As the freezing wind passes around the bridge, it loses heat from all directions. The road can only lose heat from its surface.

In fact, while the temperature on the road surface is dropping, the sub-surface heat underneath the road helps keep it warm enough to either prevent icing or delay its onset. Bridges will continually lose heat and freeze shortly after temperatures in the atmosphere hit the freezing point.

This phenomenon can cause problem areas as drivers suddenly hit unexpected icy conditions. Pelmorex can offer a variety of weather solutions for winter maintenance of bridges.

• Detailed atmospheric and bridge deck temperature forecasts. This is closely linked to RWIS solutions, but will take into account the very different thermal properties of various bridges. This will allow winter maintenance personnel to actively prepare for icy conditions at these trouble cold spots.
  
  
• Automated spraying systems can be installed - these work by monitoring the weather and bridge deck conditions. Using RWIS data, a computer algorithm calculates when icing conditions will occur and activates the system before the road ices. The system which Pelmorex installs utilizes state-of-the-art technology including plowable, in-pavement nozzles that can spray from the middle of the road, replacing or supplementing standard wall-mounted nozzles to cover 4 to 6 lane roads. A PC interface also allows remote site monitoring and activation of FreezeFree anti-icing liquid spray systems.