Road surface wetness as affected by evaporation, surface runoff and traffic splashing

Mats Riehm
Per-Erik Jansson

Road surface wetness governs the fate of pollutants on the road surface. The wetness is also important for estimating the risk of ice formation during winters. The road surface water is affected by evaporation, run-off and traffic induced splash and spray. Increased knowledge of how these processes govern the road surface water and how they could be modelled would help to improve the possibility to abate problems with raised levels of air pollutants, as well as traffic safety issues by facilitating optimization of the use of anti- and de-icing chemicals. The aim of this study was to use a modeling tool in order to differentiate between three processes governing the loss of wetness from the road surface within a cross section of a road during two different climatic scenes (winter and spring). Two new measurement techniques were used for detailed measurements of road surface wetness across a road to validate the model. It could be concluded that the changes in wetness on the road can be simulated from general simple weather and traffic information. Furthermore, the wetness across the road is very heterogeneous and can be described by a distribution of regulating parameter values. The presented model application has a potential for real time application on roads and within a region and also for predictions of future conditions by using weather forecast data.



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