NORTRIP - Non-exhaust road traffic induced particle emissions: development of a model for assessing the effect on air quality and exposure

Christer Johansson
Cecilia Bennet

The PM10 concentrations exceed the EU limit values in almost all countries in Europe. Especially, in many Nordic cities, non-exhaust particle emissions are the main reason for high PM10 levels along densely trafficked roads. This is connected to the use of studded tyres and winter time road traction maintenance, e.g. salting and sanding. The ultimate aim of the project has been to develop a process based emission model, that can be applied in any city without site specific empirical factors, for management and evaluation of abatement strategies and that is able to describe the (non-exhaust) emissions on an hourly or at least daily basis with satisfactory accuracy. The model is built upon existing road dust emission models, combined with field and laboratory measurements. The major features of the model are:

  • Road dust and salt loading is calculated based on a mass balance equation
  • Production of road dust, and subsequent emissions, are based on the total wear of road, brakes and tyres
  • Maintenance activities (e.g. salting, sanding, cleaning, ploughing) contribute to the mass balance as well as processes such as drainage and splash/spray
  • Retention of road surface dust is dependent on the surface moisture content
  • The road surface moisture is calculated based on a mass balance equation for surface water and ice
  • Evaporation is based on energy balance modelling of the road surface
  • Maintenance activities (e.g. cleaning, ploughing, salt solutions) and processes (e.g. drainage, splash/ spray) are included in the moisture mass balance
  • The impact of salting on both dust retention and melt temperature is considered



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