On 11 July 2019, the Department for Environment, Food & Rural Affairs (DEFRA) released the Air Quality Expert Group’s report on non-exhaust emissions (NEE) from road traffic. This refers to particles released into the air from brake wear, tyre wear, road surface wear and re-suspension of road dust during on-road vehicle usage. There is no legislation in place to limit or reduce NEE particles.
Data from the UK National Atmospheric Emissions Inventory indicate that particles from brake wear, tyre wear and road surface wear currently constitute 60% and 73% (by mass), respectively, of primary PM2.5 and PM10 emissions from road transport, and will become more dominant in the future. Currently they contribute 7.4% and 8.5% of all UK primary PM2.5 and PM10 emissions. The national inventory indicates that half of NEE occurs on urban roads, owing to the greater braking per km than on non-urban roads and making this of especial importance in urban environments.
The most effective mitigation strategies for NEE are to reduce the overall volume of traffic, lower the speed where traffic is free-flowing, for example on trunk roads and motorways, and promote driving behaviour that reduces braking and higher-speed cornering.
The Scottish Government’s ‘Clearer Air for Scotland’ document offers definitions on the various types of particulate matter [PM] mentioned above.
Source: DEFRA, 11 July 2019