Road traffic has been identified as a significant source of pollution in 95 per cent. of the air quality management areas (designated by local authorities) declared so far.
Local air quality assessments include a basic screening process to determine vehicles’ impact on air quality. Typically, this considers traffic as consisting only of light and heavy duty vehicle types, assigning average levels of emissions to each of these in order to model their air quality impact on the surrounding area. Although this method does not apportion a fraction of the overall level of air pollutants directly to specific classes of vehicles, such as heavy goods vehicles (HGVs), it does ensure that their emissions are represented in the assessment.
Should the screening process identify a likely failure of air quality objectives, a further, more detailed level of assessment is undertaken to establish whether an air quality management area is necessary. These methods of assessment all consider the specific contribution of HGVs to ambient air pollution.
No specific national assessment of the impact of HGV traffic has been made for the areas mentioned in (b), (c) and (d). Terrestrial special protection areas are also notified as sites of special scientific interest (SSSIs). Natural England data on the reasons for unfavourable condition on SSSIs identifies that 18,524 hectares of SSSI land are adversely affected by air pollution. However the impacts of air pollution and identification of air pollution as an adverse activity affecting site condition are currently considered to be under reported. Furthermore SSSI condition is not disaggregated to identify different sources of air pollution. Individual assessments of the impact from air pollution have been made in respect of specific sites.