Non-exhaust emissions from road traffic

Road traffic has long been recognised as a major source of air pollution due to emissions of a range of gaseous pollutants, most notably carbon monoxide, oxides of nitrogen and volatile organic compounds, as well as particulate matter. The gaseous pollutants are present in exhaust emissions, and, until recently, the dominant source of particles was also from the vehicle exhaust. However, road transport is also an important source of ‘non-exhaust emissions’ (NEE) of particles, which are produced from frictional processes associated with vehicle usage: predominantly from brakes, tyres and the road surface. Whilst regulations set by the European Union have led to progressive reductions in the emissions of the regulated gaseous pollutants and of particulate matter from the exhausts of new vehicles, the non-exhaust emissions are not currently targeted by emissions regulations. Therefore, as the exhaust emissions have fallen, the proportion of non-exhaust emissions to the total emissions from road traffic has increased. Data from the UK National Atmospheric Emissions Inventory (NAEI) indicate that emissions of non-exhaust particles from road transport already exceed those from the exhaust, and their proportion is projected to increase in the future. Therefore, to achieve further improvements to PM2.5 and PM10 air quality relating to road transport sources requires attention to reducing NEE, and not solely on approaches focused on lowering exhaust emissions. However, quantitative data on the magnitude of non-exhaust emissions are sparse and highly uncertain, particularly when compared to data for exhaust emissions. The exact contribution of non-exhaust emissions to air quality locally and nationally is therefore currently subject to considerable certainty. The aim of this AQEG report is to summarise current evidence for the non-exhaust emissions of particles from road transport at the point of on-road usage.

  • Record URL:
  • Supplemental Notes:
    • Report prepared for Department for Environment, Food and Rural Affairs; Scottish Government; Welsh Government; and Department of the Environment in Northern Ireland
  • Corporate Authors:

    UK Air


    Air Quality Expert Group

  • Publication Date: 2019-7


  • English

Media Info

  • Pagination: 89p

Subject/Index Terms

Filing Info

  • Accession Number: 01714723
  • Record Type: Publication
  • Source Agency: ARRB Group Limited
  • Files: ATRI
  • Created Date: Aug 26 2019 11:22AM