Factors Influencing Thermal Mapping

The pattern of temperature across a highway or runway is determined by local environmental factors and prevailing weather conditions. On any given winter night, this will lead to some sections always being relatively warmer or colder than others.

The combination of local features and how they react to prevailing weather conditions generates a unique signature of each highway/runway. Thermal Mapping is used to help the winter maintenance practitioner locate and quantify temperature variations across a network.

Key influencing factors:

• Prevailing weather conditions.

• Sky view factor (exposure). This will be dictated by features such as vegetation, buildings and tunnels etc. A low sky view will tend to indicate features overhanging or close to the highway or runway. Such features will tend to inhibit night-time cooling and may help the surface to retain some of its heat. A high sky view will relate to an open environment and will tend to exhibit cold night-time pavement temperatures, as there is nothing to prevent the surface cooling.

• Altitude (temperature will tend to decrease with height).

• Proximity to the coast and major water bodies.

• Urban heat island effect.

• Cuttings, embankments, elevated sections. These are localised features that will affect the energy flux of the road/runway at that point.

• Highway/runway construction (surface material e.g. concrete/asphalt/open asphalt, and depth of construction).

• Traffic volume & flow.

 

Thermal Mapping establishes the relationship between these variables and how they interact under different weather scenarios. Thermal Fingerprints (actual survey data of pavement temperatures) and Thermal Maps (the graphical representation of the relative variations in highway/runway surface temperature across an area).